BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Kit Gallagher (QMUL) DTSTART:20200228T050000Z DTEND:20200228T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/1 DESCRIPTION:Title: Viable Gauge Choices in Cosmologies with Non-Linear Structures\ nby Kit Gallagher (QMUL) as part of Cosmology Talks\n\n\nAbstract\nLink to Video \n\nRefer ence for cosmological perturbation theory: arxiv.org/abs/0809.4944\n\nReference for Post Newtonian The ory: Gravity\, by Eric Poisson\, Cambridge University Press< /a>\n\n
\n\nIndex to Key Parts of the Talk:\n\n0:00:00 Shaun's introduction\n\n0:01:05 Kit's opening comments on the paper: compared the differences in the gauge problems in two different approac hes to approximating solutions to the Einstein field equations\; cosmologi cal perturbation theory (applicable on large scales)\; post-Newtonian grav ity (applicable on small scales)\; what the gauge problem is\; paper/book references\;\n\n0:09:12 Q&A: Next steps: Issue on large scales - next gen galaxy surveys will requi re more realistic theoretical modeling than has been done in the past\; di scussion of different approaches\; important precautions\n\n0:15:51 Why the paper's approach was not us ed before: using post-Newtonian ideas in cosmology is kind of a new th ing to do\n\n0:16:29 Two take aways from the talk\n\n0:17:37 1st slide: Cosmological Perturbation Theory\n\n0:18:56 Conceptual problems: discussion leading to explanation of the gauge problem in cosmological perturbation t heory\n\n0:27:11 Post-Newton ian gravity: capable of dealing with large density contrasts\, provide d...\n\n0:28:16 : the condit ions under which a post-Newtonian expansion can be done\; 3 conditions \n\n0:31:40 Small velocities and weak field lead to...: mathematical consequences\; small time der ivatives: equations change structure from wave equations to Poisson equati ons\n\n0:40:55 The explicit structure of all the gauge transformations\n\n0:49:17 Section IV A in paper: Spatially Flat Gauge choice\n\n0:52:13 Sectio n IV B in paper: Synchronous Gauge choice\n\n0:52:42 Section IV F in paper: N-body Gauge choice\n\n0:53:13 Section IV G in paper: Longitudinal Gauge choice: important one to look at\n\n0:57:40 Q&A on the N-body gauge \n\n1:00:00 Section V of pap er: Newtonian Motion Gauge\n\n1:04:40 Discussion on equation 89 in paper\n\n1:07:50 Applicability\n\n1:10:32 Summary\n\n1:16:17 Q&A: what are two simple things you'd want viewers to take away from this talk?\n\n1:17:45 Q&A: outside of your own research\, what do you t hink is the most interesting thing in cosmology at the moment?\n\nRefe rence for cosmological perturbation theory: https://arxiv.org/abs/0809.494 4\n\nReference for Post Newtonian Theory: https://www.cambridge.org/core/b ooks/gravity/1F0CF38A59B1E51A63C7C3138268BE5D\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Seshadri Nadathur (ICG Institute of Cosmology and Gravitation\, Un iversity of Portsmouth) DTSTART:20200319T050000Z DTEND:20200319T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/2 DESCRIPTION:Title: Voids are powerful\, free and have tantalising insights on H0\n by Seshadri Nadathur (ICG Institute of Cosmology and Gravitation\, Univers ity of Portsmouth) as part of Cosmology Talks\n\n\nAbstract\nSesh tells us how the void-galaxy cross correlation provides information about cosmolog y via redshift space distortions and (importantly) the Alcock Paczynski ef fect. The information is independent of Baryon Acoustic Oscillations (BAO) and improves error bars by up to a factor of four. The combination of voi ds and BAO have very interesting insights into the Hubble discrepancy and the late-time acceleration of the Universe.\n\nLink to video of talk: youtube.com/watch?v=Uivv hqEuVuo\n\nThe most relevant papers for this talk: arxiv.org/abs/2001.11044 and arxiv.org/abs/1904.01030\n\n
\n\nIndex to Key Parts of the Talk:\n\n00:00 Shaun's introduction\n\n00:38 Sesh's opening comments on the paper: BAO and RSD have be en studied for decades and applied to basically every spectroscopic galaxy survey but the void-galaxy cross-correlation measurement is something tha t's pretty new\n\n01:40 Q&A: what are two simple things you'd want viewers to remember about this talk? : what a void-galaxy cross-correlation is and why it tells us anything about cosmology\; the distribution of galaxies around the center of low d ensity void regions is anisotropic\, not symmetric\; details of that aniso tropy\; usefulness as another method to measure the current expansion rate of the universe\, H0\n\n04:18 Q&A: what was the motivation for this work?: interest in what can be done with voids\; by using the void-galaxy cross-correlation\, improvemen t can be made in the measurement precision of important quantities like th e expansion rate and growth structure of the universe\; can improve the pr ecision of such quantities by about a factor of two (equivalent to an incr ease in the survey volume without requiring any new data or observation ti me)\n\n08:13 First slide: Voi d-galaxy basics: the distribution of galaxies around void locations\; anisotropic in redshift space\; not looking at void size but at distortion away from sphericity\, plot showing distortion due to galaxy velocities a round voids (key segment 11:32 to 13:59)\; second and more interesting and important effect (13:59 to 17:00)\n\n17:05 Correlations in redshift space: 2 sources of anisotrop y - RSD (peculiar velocities\, growth rate) and Alcock-Paczynski effect\; why the void-galaxy correlation is a better measurement method than the st andard auto-correlation technique\n\n19:57 Breaking the RSD/AP degeneracy: the quadrupole moment o f the void-galaxy correlation function\; Fig. 3 in paper \n\n25:33 Measuring ξvg in surveys\, 1st sli de: various complications that have to be considered but left for a di fferent talk\n\n25:54 Measur ing ξvg in surveys\, 2nd slide: simulations testing\; Fig. 7 and 8 (t riangle plot showing posterior constraints on parameters of the joint RSD- AP model for the void-galaxy cross-correlation) in paper\; the important p arameters in Fig. 8 are the AP parameter and the growth rate\, they are no t strongly degenerate with each other\; were able to get a 1% measurement of the AP parameter\n\n28:27 Cosmological implications I: Factor 2x improvement in precision (comp ared to BAO + FS\, full shape of the galaxy power spectrum)\; covariance m atrix\; about a factor of 4 improvement in Fap\; information that is not a vailable from usual 2-pt or 3-pt statistics\n\n32:35 Comparing voids to bispectrum: higher order s tatistics than just the galaxy power spectrum gives more information\; le ft panel shows same BOSS data but going from power spectrum to bispectrum\ ; right panel shows going from power spectrum to power spectrum + voids\; the gain from adding voids far exceeds that from the bispectrum\n\n35:32 < a href="https://youtu.be/UivvhqEuVuo?t=2132">Cosmological implications II< /a>: direct evidence of acceleration independent of CMB and SN Ia (picked up again at 43:15)\n\n34:47 Cosmological implications III: results from using combinations of BAO\ , voids\, and Ly-a to determine H0 \n\n43:15 Back to Cosmological implications II: > 10σ evidence of late-time acceleration (>> SN Ia)\; also direct evidence for DE\n\n47: 39 the DE EoS can be constra ined better with voids included and is consistent with a cosmological cons tant: Fig. 15 and discussion in paper\n\n48:07 Recap of the take-away messages: very powerful method for analyzing data from galaxy surveys\, and it's essentially for free as don't need any new observations and it tightens cosmological const raints\; some tantalizing answers on H0 discrepancy\; the strongest late-t ime evidence for DE comes from BAO+voids and not supernovae\n\n50:07 Q&A: outside of your own research \, what do you think is the most interesting thing in cosmology at the mom ent?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Graham White (TRIUMF) DTSTART:20200326T050000Z DTEND:20200326T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/3 DESCRIPTION:Title: Light dark matter is an ideal mix of particle and cosmology\nby Graham White (TRIUMF) as part of Cosmology Talks\n\n\nAbstract\nGraham te lls us how Big Bang Nucleosynthesis (BBN) and the Cosmic Microwave Backgro und can be used to constrain the potential existence of particles beyond t he Standard Model. \n\nThe focus is on light dark matter (masses less than 1GeV)\, which escapes direct detection bounds by being too light to kick nucleons hard enough and is most interesting to cosmology because it has p recisely the masses relevant in the early universe processes we can "obser ve"\, e.g. BBN.\n\nGraham volunteered to give this talk on less than 36 ho urs notice\, so huge thanks to him for pulling something together so quick ly!!\n\nTalk video: youtube.com/watch?v=85sXsaj02yE\n\nGraham's paper: Cosmological Bounds on sub-GeV Dark Vector Bosons from Electromagnetic Energy Injection\n\n
\n\nIndex to Key Parts of the Talk:\n\n00:00 Sha un's introduction\n\n00:43 Graham's opening comments \n\n01:20 Q&A: what are two simple things you'd want viewers to remember about this talk?\n\n02:49 Q&A: What is the motivation for this work?: focus is on the mass rang e between 1 MeV and 1 GeV\, a particularly interesting region for cosmolog ical constraints \n\n08:36 1st slide: Where to look for hidden sectors\n\n09:44 Why bother with cosmology?: tie-in with co nstraints previously identified\n\n10:51 Big Bang nucleosynthesis: 3 slides\n\n14:08 Electromagnetic Cascade: several proces ses outlined\; one very important thing that has been a little neglected i s final-state radiation\n\n15:22 Photon spectrum: 2 slides\; conventional wisdom is to use the univ ersal spectrum method\, but it breaks down in this sub-GeV case for severa l reasons\, see top of pg3 of paper\n\n16:09 the universal spectrum method results in orders of magnitu de differences from the exact calculations at this scale: it was previ ously known this can occur near or below the GeV scale\n\n17:30 Light element abundances: 3 observ ables trying to constrain\n\n18:53 Boltzmann equations\n\n19:46 Nucleon-destruction\n\n20:42 Benchmarks for photon injection\n\n23:38 Benchmarks for electron injection\n\n24:28 Monochromatic inj ection: Figure 7 in paper\n\n26:08 Other model independent constraints: 2 slides\; Fig. 2 in p aper\n\n28:01 Model dependen t constraints: 4 slides\; Figs. 1 and 3 in paper\n\n31:51 Discussion on the Lithium problem\n\ n34:10 CMB ionization constr aints: 3 slides\n\n38:05 CMB spectral distortion constraints: 2 slides\n\n38:57 COBE and PIXIE Limits: Fig. 5 in paper \n\n39:23 Freeze in abundanc es: 2 slides\; section 5.1 of paper\n\n42:04 Parameter constraints: Fig. 6 in paper\n\n45:25 < a href="https://youtu.be/85sXsaj02yE?t=2725">Conclusions\n\n46:00 Q&A: Next steps\n\n49:15 Q&A: Recap of take-away message s\n\n49:55 Q&A: outside of your own research\, what do you think is the most interesting thing in cosmology at the moment?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Julien Lesgourgues (Institut für Theoretische Teilchenphysik und Kosmologie\, RWTH Aachen University) DTSTART:20200402T050000Z DTEND:20200402T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/4 DESCRIPTION:Title: Cosmology won't measure individual neutrino mass states\nby Jul ien Lesgourgues (Institut für Theoretische Teilchenphysik und Kosmologie\ , RWTH Aachen University) as part of Cosmology Talks\n\n\nAbstract\nJulien tells us about the cosmological effects of different neutrino mass states (i.e. the same sum of masses\, but different masses for each individual n eutrino - e.g. "normal" vs "inverted"). \n\nThere are effects\, but they'r e all very small and not even the best future experiments will distinguish them.\n\nNon-standard model neutrinos would still have interesting effect s\, but it seems that cosmology's insight on the SM ones will be limited t o the sum of the masses.\n\nVideo of talk\n\nPaper: [2003.03354] What will it take to measure individual neutrino mass st ates using cosmology?\, by Maria Archidiacono\, Steen Hannestad\, Juli en Lesgourgues\n\nSupplemental info: Review of paper by Sunny Vagnozzi\n\n\n\nIndex to Key Parts of the Talk:\n\n[00:01] Shaun's intro to the topic and Julien's work\ n\n[00:32] Julien's opening co mments summarizing the paper's findings \n\n[01:46] Q&A: what are two simple things you'd want view ers to remember about this talk?: two take-home messages\, one for par ticle physicists and one for cosmologists\n\n[04:01] Q&A: what is the motivation for this work?: th ere were many papers addressing the same question but situation not crysta l clear\, this work used Bayesian evidence which was not used before and a lso discusses in detail the physical effects of different mass splittings on the cosmological observables\n\n[05:21] Title page from the paper and collaborators\; definitions of acronyms and proxies that will be referred to: normal (NH)\, inverted (IH)\, and degenerate (DH) hierarchy\; Proxy 1 (1 massive + 2 massless)\, Proxy 2 (2 massive + 1 massless)\n\n[08:09] Plot of total neutrino mass vs lightest\, commentary on Fi g. 1 of paper\n\n[11:23] Total background density evolution for IH and NH compared to the equivalen t DH model\, Fig. 2b from paper\n\n[15:11] CDM density perturbation evolution for IH or NH compared to the equivalent DH model\, Fig. 4a\n\n[17:06] The power spectrum of the different models\; Fig. 5 from paper \n\n[20:54] Observable galaxy power spectrum\, Fig. 7a: probably the most intere sting plot\, reformulated in terms not of the theoretical matter power spe ctrum but of the real observable power spectrum that Euclid will measure\; all done analytically or semi-analytically with CLASS code and starting f rom linear observables\n\n[25:45] Observable weak lensing\, Fig. 7b\n\n[26:13] Ratio of the lensed angular power spectra of te mperature\, E-mode polarization\, and B-mode polarization for the same mod els\, Fig. 6b\n\n[28:54] Mass reconstruction forecast using DH instead of fiducial NH/IH + Bayesia n evidence ratio of "correct" / DH\; Fig. 8\n\n[32:04] Julien's recap comments on the paper's find ings\n\n[36:28] Q&A: Nex t steps\n\n[39:05] Q&A: outside of your own research\, what do you think is the most interesting t hing in cosmology at the moment?\n\n[41:35] Q&A on spatial curvature\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Deanna C. Hooper (University of Brussels) DTSTART:20200409T060000Z DTEND:20200409T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/5 DESCRIPTION:Title: CMB spectral distortions are a prime untapped resource\nby Dean na C. Hooper (University of Brussels) as part of Cosmology Talks\n\n\nAbst ract\nDeanna tells us about what we could learn from future measurements o f the spectral distortions in the CMB\, as well as how spectral distortion s complement current and future measurements of CMB anisotropies. She also discusses CLASS (v3.0)\, the code you can (very soon) use to calculate pr edictions for both.\n\nThere is a guaranteed spectral distortion signal to detect within ΛCDM and the possibility to constrain many possible deviat ions\, including primordial black holes and decaying dark matter. In fact\ , we can detect the signal even if the PBHs and/or decaying dark matter on ly make up one part in a million of the total dark matter!\n\nWhy have we waited so long (and are still waiting) for an updated measurement after CO BE-FIRAS\, which is now more than 25 years old?! I don't know\, but hopefu lly it won't be another 25.\n\nVideo of Talk\n\nPaper: [1910.04619] The synergy between CMB spectral distortions and anis otropies\, by Matteo Lucca\, Nils Schöneberg\, Deanna C. Hooper\, Jul ien Lesgourgues\, Jens Chluba\n\nCLASS\, the Cosmic Linear Anisotropy Solving System\n\nSupplemental Info: \n\nDeanna's 20-tweet thread on this paper\n\nDeanna also does live streams about cosmology/the universe on Periscope. These a re aimed at a general audience: https://www.pscp.tv/DCHooper91/1LyxBNjVbzjxN\n\n
\n\n< b>Index to Key Parts of the Talk:\n\n[00:02] Shaun's intro to the topic and Deanna's work\n\n[00: 45] Deanna's opening comments on this work: spectral distortions (SDs)\, deviations from a perfect b lack body spectrum\, have very much not been exploited to full potential\; a whole new region of parameter space can be explored\; first step was to implement the full calculation of SDs in the standard Boltzmann code CLAS S\; can now produce both the anisotropy and SD predictions for the same mo del\n\n[01:52] Q&A: what are two simple things you'd want viewers to remember about this talk?: (1) SDs are the future of CMB\, even with future CMB missions\; SDs will allo w several orders of magnitude improvements in some regions of parameter sp ace\, and (2) we now have a very powerful tool in CLASS v3 which computes SDs in parallel with anisotropies.\n\n[02:33] Q&A: what is the motivation for this work?: there is only one observation of the spectrum of CMB photons from COBE-FIRAS 25-yea rs ago\, with deviations of 10^-5\; but even with ΛCDM\, SDs are clearly predicted on the order of 10^-8\; if an SD mission does not measure anisot ropies at 10^-8\, it means ΛCDM is wrong\; other models also predicting S Ds\; an SD mission could distinguish between models\; observation is reall y lagging behind the theory\; SDs are extremely well understood\, studied for 30-40 years\; improvements in code\, mainly by Jens Chluba\; SD missio ns have been proposed but not yet funded\n\n[05:42] Q&A (an aside): Why is it taking so long for a new mission to probe SDs?: problem of foreground removal\; perhaps overloo ked as only a small part of the community is pushing for this\; gaining mo re and more attention now\; being able to test the predictions of ΛCDM is something we should be doing\; NASA roadmap includes SDs but nothing offi cially approved yet\; feasible to have measurements within 15-20 years\n\n [07:20] Returning to motivati ons: paper is long but intended as a review of the whole formalism whi ch streamlines earlier literature and details of the new CLASS code\n\n[08 :52] Slide of paper title pag e and collaborators\n\n[09:07] Main Technicalities of Spectral Distortions: 4 contributions to the total distortion to the photon intensity spectrum\; other comments on frequency bins\, amplitude of the SDs\, heating function\, branching ratio s\n\n[17:10] Branching ratio s slide: CLASS calculations plot of the 4 distortion types\n\n[21:42] SDs to the total photon inte nsity caused by ΛCDM processes and basic extensions: testable predict ion of ΛCDM if we had the satellite to do it\n\n[24:20] SDs to the total photon intensity caused by D M decay and annihilation: Decaying DM can be constrained by SDs\; Fig. 1 left panel and Fig. 2 right panel in paper\n\n[25:40] Heating rate produced by DM decay and annihil ation: Fig. 4 left panel in paper\n\n[26:20] SDs to the total photon intensity caused by PBH evapo ration: Figure 5 right panel in paper.\n\n[27:10] Making mock data to see what we'd be able to do with future missions\n\n[28:26] Constraints from different current and future missions for ΛCDM + n_run: 5 different cases involving combinations of Planck\, FIRAS\, P IXIE\, LiteBIRD\, CMB-S4\, PRISM\; Fig. 7 in paper\n\n[33:10] Constraints on decaying DM fraction as a function of the particle lifetime: Deanna's favorite plot from the pa per\, Fig. 8\; the part of the plot where spectral distortions are needed\ ; different regions of parameter space\, one can be constrained by anisotr opies and the other with SDs\n\n[35:55] Constraints on PBHs as a function of their mass: they foun d a new way to study PBH evaporation\; Fig. 9 in paper\n\n[39:05] Q&A about using CLASS v3\n\n[40: 19] Next Steps: 2 papers in the pipeline using this framework\; 3rd paper on foreground removal\n\ n[42:56] Reiterating 2 takea way points from talk\n\n[43:40] Q&A: outside of your own research\, what do you think is the most interesting thing in cosmology at the moment?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Omar Darwish (DAMP\, University of Cambridge) DTSTART:20200416T060000Z DTEND:20200416T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/6 DESCRIPTION:Title: Lensing maps are great\, but they're even better with the tSZ effec t removed!\nby Omar Darwish (DAMP\, University of Cambridge) as part o f Cosmology Talks\n\n\nAbstract\nOmar tells us about the excellent quality lensing map he's produced with the Atacama Cosmology Telescope collaborat ion. You honestly won't believe how well this lensing map correlates with the cosmic infrared background (sorry about the clickbait). \n\nThis map w ill be incredibly useful to cross-correlate with any dataset of tracers in side the relatively large window of ACT observations. It will be public ve ry soon\, so once it is you should definitely be using it!\n\nOmar also ex plains how he and the collaboration\, for the first time\, removed the ann oying thermal Sunyaev–Zeldovich contamination that ordinarily produces a ~10% bias in sigma8 (and thus any other cosmological parameter correlated with sigma8).\n\nVi deo of Talk\n\nPaper: [2004 .01139] The Atacama Cosmology Telescope: A CMB lensing mass map over 2100 square degrees of sky and its cross-correlation with BOSS-CMASS galaxies\n\n Review of paper by Sunny Vagnozzi\n\n
\n\nIndex to Key Parts of the Talk:\n\n[00:02] Shaun' s introduction\n\n[00:23] Omar's opening comments on this work\n\n[02:24] Q&A: what are two simple things you'd want viewers to remember about this talk?\n\n[05:32] Q&A: what is the motivation for this work?\n\n[07:52] < a href="https://youtu.be/BnFxAFrxbtI?t=472">Title slide of talk and collab orators: ACTPol lensing maps and foreground-cleaned galaxy correlation s\; with Mathew Madhavacheril\, Blake Sherwin\, and the ACT Collaboration\ n\n[08:45] CMB Lensing Intro< /a>: lensing deflection field\; lensing convergence field κ \n\n[12:02] < a href="https://youtu.be/BnFxAFrxbtI?t=722">CMB Lensing Reconstruction Bas ics\n\n[14:27] ACT Experi ment: effective area BOSS-North + Deep56 ~ 2100 sq deg\; overlap with multiple surveys (BOSS\, DES\,...)\n\n[16:11] CMB Lensing from ACT: Deep56 ACTPol Lensing [16:31]\; Deep56 ACTPol Lensing vs Planck CIB [19:41] (plo t shown here is top part of Fig. 2 in paper)\; BOSS-N ACTPol Lensing vs Pl anck CIB [20:52] (bottom part of Fig. 2 in paper)\n\n[21:32] ACT CMB Lensing Maps\n\n[25:38] Many CMB Lensing x Galaxy papers\n\n[27:16] One particular systematic effect for low-z galaxy lensing cross correlations: this effect will become impor tant for AdvACT and Simons Observatory\n\n[30:44] Systematics: tSZ contamination: important for TT dominated lensing maps\; negative bias ~10 - 20%\n\n[32:06] Removing tSZ contamination: three sli des\n\n[36:07] tSZ cleaned C MB lensing maps from ILC ACT+Planck\n\n[38:20] Symmetrising gradient cleaning for foreground remov al\n\n[44:36] Minimum va riance forecasted lensing noise\n\n[45:24] Contaminated vs non-contaminated measurement\n\n[46 :07] Simple amplitude fit\; refers to Fig. 5\, pg10\, of paper\n\n[46:45] Next Steps\n\n[48:37] Conclusions\n\n[49:40] Q&A: outside of your own research\, what do you think i s the most interesting thing in cosmology at the moment?\n\nSupplement al info: A tweet thread by Shaun about this talk\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Jurek Bauer (Georg August University of Göttingen) DTSTART:20200424T060000Z DTEND:20200424T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/7 DESCRIPTION:Title: Fuzzy dark matter arising from GUT scale physics should be ruled in /out by SKA\nby Jurek Bauer (Georg August University of Göttingen) as part of Cosmology Talks\n\n\nAbstract\nJurek tells us about the prospects for constraining axion (aka ultralight aka fuzzy) dark matter with future 21cm intensity mapping survey such as SKA and HIRAX.\n\nAxion models aris ing from specific energy scales predict that an axion with a given mass wi ll only provide a certain fraction of the total dark matter. It seems plau sible that with SKA we will be able to detect ultralight dark matter even if it arises from a GUT scale axion model. An observational noise model fo r SKA was included to make this claim\, but as of yet no theoretical uncer tainty is included in the calculation.\n\nVideo of talk\n\nPaper: [2003.09655] Intensity Mapping as a Probe of Axion Dark Matter\, by Jurek B. Bauer\, David J. E. Marsh\, Renée Hložek\, Ham sa Padmanabhan\, Alex Laguë\n\n
\n\nIndex to Key Parts of the Talk: \n\n[00:02] Shaun's intro t o the topic and Jurek's work\n\n[00:57] Jurek's brief summary of the paper: we investigated the impact of ultralight axions on 21cm intensity mapping (IM) in the post-rei onization universe\; vastly increases the accessible modes\; use a data-dr iven framework for the HI power spectrum provided by the HI halo model of Padmanabhan+ 2017 (a separate Cosmology Talk is available on this at youtu.be/K8bS_52_XMk)\; etc. \n\n[02 :27] Q&A: what are two simple things you'd want viewers to remember about this talk?: (1) their HI halo model allowed extending the axion phenomenology to a completely new l evel\; it highlights the importance of the bias\, and (2) exciting prospec ts with near future surveys (SKA1MID\, HIRAX\, CMB-SO)\, which in combinat ion can test the theoretical predictions\n\n[03:54] Q&A: what is the motivation for this work?: ult ralight axions (ULAs) are a well-motivated DM candidate\, and (2) work by Carucci+ 2017 (more at [29:0 2])\n\n[08:39] First slid e: What is 21cm Intensity Mapping?: includes commments on Fig. 13\, pg 12\, of the paper\n\n[10:40] Axion Physics: large de Broglie wavelength introduces scale-dependent pressure\; ULAs suppress the matter power spectrum on small scales\, depen ding on their mass\; axionCAMB used for computation. See section 2.1 and F ig. 1 of the paper.\n\n[12:57] Modeling the 21cm signal\; halo mass function (HMF)\; halo bias\; ne utral hydrogen - halo mass relation\; neutral hydrogen density profile\; r edshift space distortions are ignored in the present study\, a conservativ e assumption (see pg4 of paper)\n\n[16:47] HI Halo Model: comments based on Fig. 2\, pg4\, of pape r\n\n[17:52] Modeling the 21 cm signal: Use spherical harmonics tomography: slice survey volume int o redshift bins and do spherical harmonic decomposition for the surface\, similar to CMB\n\n[19:30] Ac commodating Axions: comments on Fig. 3 on pg6 of the paper\n\n[22:39] HMF and HI bias: comment s on Figs. 4 and 5\, pg6\, of the paper\n\n[26:20] The HI Power Spectrum for the ULAs: comments on Fig. 6\, pg 7\, of the paper\n\n[29:02] Comparison to HI Power Spectrum simulation by Carucci+ 2017: similar trend but an offset\; comments on Fig. 7\, add'l details on pg 8 of paper\n\n[32:26] Degene racy Structure: 4 parameters are highly degenerate\; ways to break deg eneracies\; Fig. 10 comments\, add'l details on pg11 of paper\n\n[34:44] < a href="https://youtu.be/bMlrDOWw978?t=2084">Error on Axion Fraction - Ove rview: comments on Fig. 9\, pg10\, of the paper\n\n[38:40] Combining IM with CMB-SO: comments on Fig. 12\, pg12\, of the paper\n\n[39:28] SKA1MID and HIRAX surveys: exclusion limits\; comments on Fig. 14\, pg13\, of the paper\n\n[44:08] Q&A: What's next?\n\n[44:58] Two takeaway comments\n\n[45:41] Q&A: outside of your own research\, what do you think is the most interesting thing in cosmology at the moment?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/7/ END:VEVENT BEGIN:VEVENT SUMMARY:W. L. Kimmy Wu (KICP at the University of Chicago) DTSTART:20200501T060000Z DTEND:20200501T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/8 DESCRIPTION:Title: Planck lensing and line of sight BAO in mild tension. A vital clue in the Hubble mystery?\nby W. L. Kimmy Wu (KICP at the University of C hicago) as part of Cosmology Talks\n\n\nAbstract\nKimmy tells us about a s ubtle but very interesting tension between Planck lensing data and line of sight Baryon Acoustic Oscillation (BAO) data.\n\nShe and her coauthors di scovered this via an intriguing mismatch between Planck and South Pole Tel escope (SPT) lensing results. The Planck and SPT power spectrum amplitudes matched\, but when combined with BAO and Big Bang Nucleosynthesis the inf erred Hubble parameters were slightly different.\n\nLike great data-detect ives they tracked the source of this discrepancy down to the mismatch betw een Planck lensing and line of sight BAO. Why the line of sight BAO might be causing this is unclear. On the Planck lensing side\, it has something to do with the shape of the lensing power spectrum\, e.g. the location of the peak - because SPT only measures the power spectrum's tail and so is o nly sensitive to the amplitude.\n\nThe result is definitely interesting\, and unknown by the community until now (as far as I'm aware). Whether it i s a red herring or a vital clue in the hunt to solve the Hubble mystery re mains to be seen. But it should provide fuel for both model builders and h unters of systematic errors trying to solve this mystery.\n\nVideo of talk\n\nPaper: [2004.10207] Hubble constant tension between CMB lensing and BAO measurements\, by W.L. Kimmy Wu\, Pavel M otloch\, Wayne Hu\, Marco Raveri\n\n
\n\nIndex to Key Parts of the T alk:\n\n[00:02] Shaun's int ro to the topic and Kimmy's work\n\n[01:10] Kimmy's brief summary of the paper: A tension metric \, the update difference in mean parameters\, is applied to trace the orig in of the observed differences in H0 between Planck and SPT lensing measur ements when both are combined with BAO measurements with a baryon density prior\n\n[01:52] Q&A: what ar e two simple things you'd want viewers to remember about this talk?: ( 1) a surprise result\, the driver of the tension between the two data sets is a mild tension between the Planck lensing data set and BAO measurement s (in particular\, the line-of-sight BAO measurements appear to be an outl ier)\, and (2) a very good use case for this update difference in mean ten sion metric\, it allows the data to tell what are the interesting paramete r directions to look at\n\n[04:42] Q&A: what is the motivation for this work?: A little history on how they stumbled across this curiosity\; first slide: Ωm\, H0 constraint s with galaxy BAO + BBN prior\; SPTpol lensing and Planck lensing are cons istent\, but there is something about adding BAO and BBN that draws out va rious features of the lensing spectrum that causes a difference in the H0 inference \n\n[11:04] Brief overview of CMB lensing measurements\n\n[12:51] Planck and SPTpol lensing measurements\n\n[14:1 8] The BAO measurements \ n\n[15:37] Perpendicular and Parallel BAO\n\n[17:00] Tension metric: update difference in mean parameters\, Qudm: a modifie d version of the simpler metric\, difference in mean parameters\, which wo rks well if both data sets are Gaussian\; Qudm is useful where A's posteri or is Gaussian but B's is not\, but where A + B are sufficiently approxima tely Gaussian\; usefulness of KL decomposition (more details in the paper in section II: Quantifying Tensions)\n\n[22:51] Choosing the Parameter basis\n\n[26:35] Qudm: BAO + BBN + SPTpol lens update w ith Planck lens: How much fractional constraining power each KL mode c ontributes to a parameter\n\n[30:17] Qudm: BAO + BBN update with Planck lens\n\n[32:59] Parallel and perpendicular BAO measure ments are consistent\n\n[35:37] Parallel BAO contributes most to the mild tension between Planck l ensing and BAO+BBN\n\n[39:50] High best-fit Ωm to parallel BAO => high H0\n\n[40:53] Redshift slope in parallel BAO measu rements drives high Ωm\n\n[42:20] High Ωm strongly ruled out\n\n[44:23] Q&A: Where to next?\n\n[47:30] Q&A: What might be causing the Hubble ten sion?\n\n[50:18] Q&A: ou tside of your own research\, what do you think is the most interesting thi ng in cosmology at the moment?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Adam Riess (Johns Hopkins University) DTSTART:20200506T060000Z DTEND:20200506T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/9 DESCRIPTION:Title: Cepheid crowding is not the cause of the Hubble tension\nby Ada m Riess (Johns Hopkins University) as part of Cosmology Talks\n\n\nAbstrac t\nAdam tells us about what he and collaborators considered to be the lead ing candidate for a systematic error in the SHOES measurement of the expan sion rate of the Universe. This is "Cepheid crowding"\, the possibility th at background sources change our interpretation of Cepheid brightness\, ru ining one step in the SHOES distance ladder.\n\nThey devise a nice way to test whether the crowding is correctly accounted for and find that it is. So crowding cannot be the "explanation" of an error in the distance ladder measurement of H0.\n\nHe also stresses that both the early and late unive rse measurements of H0 are now backed up by multiple different measurement s. Therefore\, if the resolution isn't fundamental physics\, then no singl e systematic can entirely solve the tension.\n\nWe also discuss a few topi cs around the H0 tension\, including what resolution of the tension he wou ld pick as most likely if forced to gamble (answer: a deviation from vanil la ΛCDM in the early universe)\n\nVideo of talk\n\nPaper: [2005.02445] The Accuracy of the Hubble Constant Measurement V erified through Cepheid Amplitudes\, by Adam G. Riess\, Wenlong Yuan\, Stefano Casertano\, Lucas M. Macri\, Dan Scolnic\n\n
\n\nIndex to K ey Parts of the Talk:\n\n[00:02] Shaun's intro to the topic and Adam's work\n\n[00:57] Q&A: Adam's brief summary of the paper: Cepheid crowding can be ruled out at greater than 5σ as an issue caus ing the Hubble tension\n\n[02:58] Q&A: what are two simple things you'd want viewers to remember about this talk? \n\n[04:21] Q &A: what is the motivation for this work? Of all the potential systematics to check\, why is crowding the one that you chose?\n\n[06:09] First slide: the paper and the SH0ES colleagues involved\n\n[06:49] Background on the Hubble tension problem\n\n[08:38] The distance ladder method for measuring the Hubble constant: late universe method\n\n[09:31] Representative early universe methods to dete rmine the Hubble constant: early vs late universe determinations diff er by 5-6σ (*see Adam's later comment at [37:23] on his rule of thumb to clarify what differentiates early vs late universe methods)\n\n[10:54] Why do we use Cepheid variable s tars?: includes brief comments on other calibration methods besides Ce pheids\n\n[12:38] Importance of Cepheids since there aren't enough supernovae to build the distance lad der just from SNe\n\n[13:14] Cepheids and Crowding - the non-trivial challenge: idealized situa tion vs reality for accurate photometric measurements\; cannot resolve the non-uniform background under Cepheids but that must be accounted for to m easure accurate photometry\; image showing what crowding is\; how to figur e out how much crowding there is\; measuring the offset or bias that resul ts on average from the other field stars that are crowding into the resolu tion element\; extra wrinkles\; possibly the most significant challenge fo r Cepheid measurements beyond 20 Mpc is crowding and blending from redder stars particularly in near-infrared observations (Wendy Freedman quote)\n\ n[15:44] Amplitudes Provide < i>Direct Measure of Cepheid Crowding: crowded flux is bigger fract ional contribution when Cepheid at minimum\, which compresses the light cu rve amplitude\; mathematical relationship\n\n[18:09] Three Examples of Different Crowding Levels: NGC 1559: illustrates the amplitude compression effect from crowding\n\n[1 9:45] Step 1: Calibrate Ampl itude-period Relation with Milky Way Cepheids: Cepheid amplitudes depe nd on period\; expected amplitude as a function of period and crowding\n\n [21:01] Step 2: 224 NIR ampl itudes Measured in 4 hosts\, compare to Milky Way (benchmark): empiric ally measured amplitudes match prediction (with no free parameters) from c rowding assessed in the conventional way from local (Milky Way) regions\, confirming their accuracy for estimating the background at the (extragalac tic) Cepheid locations\n\n[23:21] Step 3: Constrain "unrecognized" crowding\, compare to Hubble tensio n: "unrecognized" crowding needed to explain Hubble tension ruled out at >5σ\n\n[25:10] So what c ould explain the Hubble tension?\n\n[32:56] Future Prospects: Improvements coming in the next coup le years\n\n[34:50] Q&A: If you had to guess right now\, what is the most probable explanation on either the theory or observational side?\n\n[37:23] *Adam's rule of thumb to clarify what differen tiates late universe vs early universe methods\n\n[39:13] Q&A: could a breakdown in the FRW metric at late times be an explanation?\n\n[41:10] Q&A: outside of your own research\, what do you think is the most interesting thing in cosmology at the moment?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/9/ END:VEVENT BEGIN:VEVENT SUMMARY:J. Colin Hill (Columbia University) DTSTART:20200515T060000Z DTEND:20200515T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/10 DESCRIPTION:Title: Early dark energy doesn't make cosmology concordant again\nby J. Colin Hill (Columbia University) as part of Cosmology Talks\n\n\nAbstra ct\nColin tells us about how even though early dark energy can alleviate t he Hubble tension\, it does so at the expense of increasing other tension. Early dark energy can raise the predicted expansion rate inferred from th e cosmic microwave background (CMB)\, by changing the sound horizon at the last scattering surface. However\, the early dark energy also suppresses the growth of perturbations that are within the horizon while it is active . This mean that\, to fit the CMB\, the matter density must increase (and the spectral index becomes more blue tilted). The consequence is that the matter power spectrum should get bigger.\n\nIn their paper\, Colin and his coauthors show that this affects the weak lensing measurements by DES\, K iDS and HSC\, and therefore including those experiments in a full data ana lysis makes things discordant again. The Hubble parameter is pulled back d own\, restoring most of the tension between local and CMB measurements of H0\, and the tension in S_8 gets magnified by the increased mismatch in th e predicted and measured matter power spectrum.\n\nIt is also worth noting that\, if you exclude the local measurements of H0\, there is no preferen ce for early dark energy in the data.\n\nThere is hope\, perhaps. If the s ound horizon could be changed without altering the growth of perturbations that might still be a valid resolution\, but it is unlikely to be caused by early dark energy (alone).\n\nVideo of talk\n\nPaper: [2003.07355] Early Dark Energy Do es Not Restore Cosmological Concordance\, by J. Colin Hill\, Evan McDo nough\, Michael W. Toomey\, Stephon Alexander\n\nReview of paper by Sunny Vagnoz zi\n\n
\n\nIndex to Key Parts of the Talk:\n\n[00:02] Shaun's intro to the topic and Colin' s work\n\n[01:15] Colin's summary of the 2003.07355 paper\n\n[04:52] The broader context to Colin's motivation for this work< /a>\n\n[08:16] First slide: T he Hubble Constant\n\n[08:54] Early Dark Energy: earlier EDE papers\; summary plot\; the chain of reasoning leading to the EDE models with a reference to Knox and Millea for a nice review\, 1908.03663 \; EDE models decrease the physical size of the sound horizon imprinte d in the CMB - they have added flexibility due to a set of 3 additional ne w parameters that are relevant in the calculation of the physical size of the sound horizon\n\n[12:27] How the EDE model has been implemented from a more physical perspective: a new (pseudo)-scalar field important prior to recombination\, whose en ergy density contribution decays away rapidly just before the redshift of last scattering\; the mass of the scalar field needs to be ~ 10 ^-27 eV\n\ n[17:36] The actual paramete rs used to describe this model: 3 physical parameters - mass of the fi eld\, a decay constant\, and its initial position on the potential\; these are converted into phenomenological parameters which are more closely rel ated to what the data can actually constrain\; plot showing fractional con tribution of EDE to cosmic energy budget as function of z\n\n[20:05] EDE maintains a good fit to CMB p ower spectrum data with higher H0: plot shows a sub-percent difference in the TT power spectrum between ΛCDM (H0=68.21) and EDE model (H0=72.19 )\n\n[21:40] What about larg e-scale structure?: motivation for the project - no one had made a plo t of the matter power spectrum P(k)\; modified version of the Boltzmann co de\, CLASS_EDE\, is public on github\n\n[22:26] Plot of the matter power spectrum comparing ΛCDM and EDE models: the plot of their ratio highlights the significant differe nces\n\n[24:19] Parameter Sh ifts are the driver for these differences: caused by parameter shifts in the so-called normal cosmological parameters in the EDE scenario compar ed to ΛCDM\; also a noticeable shift in the scalar spectral index\n\n[27: 38] Interesting physical eff ects due to the EDE itself\n\n[30:28] Updated EDE Analysis Including Large-Scale Structure Data Se ts: includes 2 data sets not included in previous work: DES "3x2pt" fu ll likelihood and S8 constraints from HSC and KiDS\; Cobaya code used for the MCMC sampling\n\n[33:08] Inclusion of LSS Data\n\n[35:07] Inclusion of DES/HSC/KiDS: inclusion of LSS data leads to no n-detection of EDE component\n\n[36:28] Analysis without SH0ES: comparing all data sets without SH OES\; looking at the posteriors in the EDE parameter space\; broadening of error bars when analyzing EDE model\, but no major shifts seen\; H0 tensi on persists\; strong upper limit on existence of EDE component\; SH0ES is in 3.5σ tension with other data sets (even in EDE model)\; bottom line: y ou can't shift the parameters in the way that's needed for the CMB without messing up the large-scale structure data\n\n[38:42] Summary: SHOES is the only data set driving preference for EDE (moderate evidence\, ~ 2σ)\n\n[40:43] Physical Priors: uniform priors on f_EDE and log(z_c) are very non-uniform on physical scalar field parameters f a nd m\n\n[41:34] Final Summar y: \n\n\n[42:45] Q&A: Where to next?: upcoming release of ACT c osmological parameter measurements in the next couple months\; the observa bles that dominate the constraining power are different between ACT (TE) a nd Planck (TT).\n\n[44:19] Q &A discussion on the sound horizon issue): to be consistent with LSS\, the sound horizon would need to be changed (lowered) in a way that does n ot then act to suppress the growth of pertubations\n\n[45:49] Q&A: what do you think is the most proba ble explanation of H0 tension?\n\n[48:13] Q&A: Outside of your own research\, what do you think is the most interesting thing in cosmology at the moment?\n\nOther Paper References:
\n[1811.04083] Early Dark Energy Can Resolve The Hubble Tension\, by V. Poulin\, T. Smith\, T. Karwal\, M. Kamionkowski
\n[1908.06995] Oscillating scalar fields and the Hubble tension: a resolution with novel signatures\, by T. Smith\, V. Poulin\, M. Amin< br>\n[1905.12618] Acoustic Dark Energy: Potential Conversion of the Hubble Tension\, by M. Lin\, G. B enevento\, W. Hu\, M. Raveri
\n[1904.01016] Rock 'n' Roll Solutions to the Hubble Tension\, by P. Agrawal\, F. Cyr-Racine\, D. Pinner\, L. Randall\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Hamsa Padmanabhan (CITA\, University of Toronto) DTSTART:20200529T060000Z DTEND:20200529T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/11 DESCRIPTION:Title: The overlap between HI halo modelling and cosmology\nby Hamsa Padmanabhan (CITA\, University of Toronto) as part of Cosmology Talks\n\n\ nAbstract\nHamsa tells us about how baryonic gases arrange themselves insi de galaxies\, specifically in the context of the HI halo model (with some deviation to discuss other gases like molecular hydrogen and carbon monoxi de).\n\nThis is a great talk in its own right\, full of really useful info rmation for cosmologists who want to know how intensity mapping\, etc\, wi ll be used for cosmology - but\, it also acts as a good companion talk to Jurek Bauer's talk on constraining axion dark matter using intensity mappi ng (https://www.yout ube.com/watch?v=bMlrDOWw978). Hamsa was a coauthor on Jurek's paper an d the expert in that collaboration on the HI/intensity mapping part.\n\nTh is video builds up to eventually being about this paper\, https://arxiv.org/abs/2002.01489\, however in getting there it covers the whole background of modelling HI and other baryonic gases within galaxies in an information packed\, but accessible w ay.\n\nVideo of talk \n\nPaper: [2002.01489] New empirical constraints on the cosmological evolution of gas and stars in g alaxies\, by Hamsa Padmanabhan\, Abraham Loeb\n\n
\n\nIndex to K ey Parts of the Talk:\n\n[00:01] Shaun's introduction to Hamsa's work\n\n[01:12] Hamsa's brief summary of the paper and her wor k\n\n[03:27] Q&A: what ar e two simple things you'd want viewers to remember about this talk?\n\ n[06:22] Q&A: What problems w ere unsolved that motivated this work?\n\n[09:21] Details on the paper: "everything here is mor e or less centered around this innovative technique known as intensity map ping...it's been gaining a lot of attention over the past few years and in fact over the last decade"\n\n[10:02] What intensity mapping is: "much faster and much cheaper" th an other methods\; "it can be done for different lines\, for different tra cers of large scale structure (e.g.\, 21cm\, CO\, C+)"\n\n[11:2 2] Impact of astrophysics and the "astrophysical systematic" that needs to be quantified: "how much does the uncertainty in the astrophysics (foreground) propagate into the power spectrum of 21cm intensity fluctuations?"\n\n[15:27] Efficiently modeling the astrophysics: " the most natural way to do this seems to be by using a halo model framewor k" for associating baryonic gas with dark matter halos\n\n[17:44] The HI halo model and its free param eters\n\n[25:02] Availab le HI data\n\n[27:54] Co nstraints\n\n[28:54] Bes t fit halo model\n\n[31:04] Insights\n\n[36:46] Cosmology and astrophysics constraints: precision and accuracy\n\n[37: 50] CO contraints: z ~ 0.3\n\n[38:14] A halo model f or carbon monoxide\n\n[40:54] Reverse engineering: "Abundance matching\; combine HI constraint s with empirical evolution of stellar-halo relations"\n\n[42:36] Stellar mass buildup: Commentary on Figures 2 and 4 in the paper\n\n[46:20] Summary

\n \n[49:48] Future work \n\n[51:36] Q&A: Outside of your own research\, what are your though ts on what's most interesting in cosmology currently?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Clare Burrage (University of Nottingham) DTSTART:20200605T060000Z DTEND:20200605T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/12 DESCRIPTION:Title: Atomic lab experiments rule out almost all of chameleon dark energ y model-space\nby Clare Burrage (University of Nottingham) as part of Cosmology Talks\n\n\nAbstract\nClare tells us about how chameleon dark ene rgy models can be very tightly constrained by simple atomic lab experiment s (well\, simple compared to particle accelerators and space telescopes). \n\nChameleon models were popular for dark energy because their non-linear potentials generically create screening mechanisms\, which stop them gene rating a "fifth force" even though they couple to matter. This means we wo uldn't normally see their effects on Earth. However\, in a suitably precis e atomic experiment the screening can be minimised and their effect measur ed.\n\nIn less than five years\, Clare and her collaborators went from the idea to the completed experiment\, which rules out almost all of the viab le parameter space where a chameleon model can explain dark energy. Only a tiny sliver of allowed space is left\, albeit at fundamental parameter va lues that would be natural ones - so maybe the chameleon is hiding right t here waiting?\n\nVid eo of talk\n\nMost relevant paper: [1812.08244] Experiment to detect dark energy forces using atom in terferometry\, by Dylan Sabulsky\, Indranil Dutta\, E. A. Hinds\, Benj amin Elder\, Clare Burrage\, Edmund J. Copeland\n\n
\n\nIndex to Key Parts of the Talk:\n\n[00:02] Shaun's intro to the topic and Clare's work\n\n[01:15] Clare's introductory brief comments\n \n[01:45] Q&A: what are a cou ple things you'd want viewers to remember about this talk?\n\n[02:27] Q&A: what is the background m otivation to your recent work and to this topic in general?\n\n[04:17] Q&A: In the near past\, what were the specific problems about this?\n\n[06:25] First slide: A Very Old Idea The types of ex periments we're going to talk about is the idea of testing the equivalence principle...What we're going to see is that these theories of dark energy \, or modified gravity\, or scalar fields kind of related to dark energy\, give you a reason to expect that under certain circumstances\, light obje cts or small objects would fall faster than large ones...that they feel an additional force essentially...and the interesting physics is why that on ly happens under certain circumstances\n\n[07:42] The standard picture: If the New Physics is Linear\n\n[10:55] If the New Physi cs is Non-Linear: Screening Mechanisms\n\n[12:43] The Chameleon A scalar field with canonical k inetic terms\, non-linear potential\, and direct coupling to matter. (astro-ph/0309300)\n\n[15 :58] Varying Mass Dynamic s governed by an effective potential. Non-linearities in the potential mea ns that the mass of the field depends on the local energy density.\n\n[17: 04] Chameleon Screening (1412.6373)\n\n[23:21] Why Atoms? (1408.1409)\n\n[25:51] Atom Interferometry\n\n[30:17] Atom Interferometry for Chameleons (1812.08244\, Experiment to de tect dark energy forces using atom interferometry)\n\n[32:04] Imperial Experiment\n\n[40:23] Combined Chameleon Constraints (1609.01192 and 1709.09071)\n\n[41:08] Summary\n\n[46:43] Clare's work in large collaboration atomic exp eriment proposals\n\n[48:15] Q&A: Where to next?\n\n[49:47] Q&A: Outside of your own research\, what do you think is the m ost interesting thing in cosmology at the moment?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Amanda Weltman (University of Cape Town) DTSTART:20200611T060000Z DTEND:20200611T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/13 DESCRIPTION:Title: Fast radio bursts and cosmology\nby Amanda Weltman (University of Cape Town) as part of Cosmology Talks\n\n\nAbstract\nAmanda Weltman te lls us about fast radio bursts (FRBs)\, which have been in the news recent ly in the context of the "missing baryons". She tells us about that measur ement (and her own theoretical work preceding it)\, but also about FRBs in general and how they'll be useful for cosmology.\n\nFRBs are what it soun ds like they are\, short bursts of radio frequency radiation detected from outside the solar system. We still don't know 100% what their origin is\, but it is possible at least some of them come from magnetars (neutron sta rs with very large magnetic fields).\n\nA very useful property of FRBs is that they have a non-zero dispersion relation in the intergalactic medium\ , because they interact with the ionised electrons in that space. This mak es it possible to measure the electron density of the inter-galactic mediu m\, and/or to measure how far the FRBs are away from us. In each case this is based on how much the frequencies within each FRB have dispersed by th e time we detect them.\n\nIf you're a cosmologist looking for a primer on FRBs and how they'll be relevant for your research\, this is the video you 're looking for.\n\n Video of talk\n\nFRB theory wiki\n\nRelevant papers:
\n[1909.02821] Probing Diffuse Gas with Fast Radio Bursts
\n[1905.07132] Fast Radio Burst Cosmology & HIRAX
\n[1810.05836] A Living Theory Catalogue for FRBs
\n\n
\n\n Index to Key Parts of the Talk:\n\n[00:02] Shaun's intro to the topic and Amanda's work: includes her comments as an expert on chameleon theory: e.g.\, the experiments don e to rule out parts of the chameleon phase space\; the original theory is still alive\; observations have ruled out a lot of alternative dark energy theories.\n\n[02:01] First s lide summarizing what fast radio bursts are and why they're useful for cos mology\n\n[04:43] Q&A: wh at are two simple things you'd want viewers to take away from this talk?\n\n[06:10] What we know ab out FRBs\n\n[08:38] Dispe rsion Measure (DM)\n\n[10:46] FRB Implications for Cosmology: implications at different scales: early universe\, late universe\, intermediate scales\; there are more imp lications than what could be listed here\n\n[15:37] Can you get better constraints on curvature using F RBs?\n\n[17:24] Dispersi on Measure of the IGM as a function of z\n\n[18:40] Contributions to DM\n\n[21:33] DM(z) can shed light on the "missing ba ryon problem": paper reference - A census of baryons in the Universe f rom localized fast radio bursts\, 2005.13161 \n\n[23:26] Tribute to Jean-Pierre Macquart\, first author of 2005.13161\, who recen tly passed\n\n[24:04] Co mments on the 2005.13161 paper: "all the baryons in the IGM that we co uldn't find\, so to speak\, are found by these FRBs\, an absolutely stunni ng result... when we wrote this paper (1909.02821) last year showing that this could be theoretically done\, it hadn't occurred to me how quickly it would be done. The rapid evolution in this field is fantastic." Includes an illustrative\, sh ort video.\n\n[26:15] Four l ocalised FRBs and what is known about them: new paper by Bhandari et al.\; much of the discussion is about the fact they all are at the edge of their host galaxies\n\n[31:20] Hydrogen Intensity and Real time An alysis eXperiment (HIRAX): similar to CHIME\, "it's a BAO inten sity mapping experiment that has FRBs as one of its science cases"\n\n[33: 15] "South Africa has made a really strong case for radio astronomy"\n\n[34:16] Prototype Array and Outriggers\n\n[34:46] Localising FRBs\n\n[35:1 6] Lessons from FRBs\n\n [35:41] Q&A: Where to next? (from the viewpoint of a theoretical cosmologist)\n\n[36:15] The FRB Catalogue\, and the FRB Theor y Wiki: references - (a) frbcat.org an d (b) frbtheorycat.org (paper - FRB CAT: The Fast Radio Burst Catalogue\, 1601.03547)\n\n[38:04] Q&A: What are some things not yet mentioned where the community shou ld work out what things to look into right away?\n\n[43:43] The importance of priors\n\n[47:36 ] Outside of your own resear ch\, what do you think is the most interesting thing in cosmology at the m oment?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/13/ END:VEVENT BEGIN:VEVENT SUMMARY:José Luis Bernal (Johns Hopins University) DTSTART:20200619T060000Z DTEND:20200619T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/14 DESCRIPTION:Title: How to tell if your cosmological approximations are accurate\n by José Luis Bernal (Johns Hopins University) as part of Cosmology Talks\ n\n\nAbstract\nJose tells us about how we can make sure our predictions fr om cosmology models can be both precise *and* accurate.\n\nVideo of talk\n\nPaper1: [2005.10384] Beware of commonly used approximations I: errors in forecasts\, by Nicola Bellomo\, José Luis Bernal\, Giulio Scelfo\, Alvise Raccanelli\, Licia Verde\n\nPaper2: [2005.09666] Beware of commonly used approximations II: estimating systematic biases in the best-fit parameter s\, byJosé Luis Bernal\, Nicola Bellomo\, Alvise Raccanelli\, Licia V erde\n\nModified CLASS c ode\n\nJose's ta lk from the Cosmology from Home conference\n\n
\n\nIndex to Key Parts of the Talk:\n\n[00:02] Shaun's intro to the topic and José's work\n\n[01:14] José's opening comments on his wor k and the topic papers\n\n[02:20] Q&A: what are two simple things you'd want viewers to remember ab out this talk?\n\n[03:24] Background details on the motivations for this work\n\n[06:15] Shaun draws parallels to an earlier Kit Gallagher talk\n\n[06:50] Start of José's slides and intro comments on the two papers\n\n [07:32] From the Precision Er a to the Accuracy Era: very different concepts\; comments on observati onal and theoretical systematics\, statistical uncertainties\; importance of blind analysis\; two outcomes of systematic errors: bias (shift in the posterior)\, misestimation (change in the shape of the posterior)\; recomm endation to use methodology of 1803.04470 (Bernal & Peacock) if you want t o be conservative\n\n[13:20] Estimating bias in parameters\n\n[17:20] Case example: Galaxy Clustering\n\n[21:34] Quick summary on nongaussianity\, then continuing on galaxy clustering\n\n[24:07] Case example 1: Cosmic magnification\n\n[30:54] Exploring 2D biases\n\n[33 :51] Case example 2: Limber Approximation\n\n[36:54] Multi-tracer Analysis: can be calculated thanks to the Multi_CLASS co de\n\n[42:04] Conclusion s\n\n[43:50] Where to ne xt?\n\n[44:42] Shaun's h ope for an eventual 'central repository' of summarized information or 'cos mology wiki'\n\n[47:36] Outside of your own research\, what do you think is the most interesting t hing in cosmology at the moment\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Natalia Porqueres (Imperial College London) DTSTART:20200703T060000Z DTEND:20200703T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/15 DESCRIPTION:Title: You can get 3D info from quasar Lyman-α absorption lines using fo rward modelling\nby Natalia Porqueres (Imperial College London) as par t of Cosmology Talks\n\n\nAbstract\nNatalia speaks about forward modelling in the context of Lyman-α absorption lines of quasar spectra. Forward mo delling essentially takes the initial conditions from your early universe model and evolves them forward to give the full observational prediction o f all measurable things\, for those specific initial conditions.\n\nThis i s different to\, e.g.\, having a "summary statistic" of this full set of i nitial conditions and/or observations that you extract to constrain your m odel. An example of a summary statistic might be a bispectrum in the late universe. The bispectrum captures some of the information lost from the po wer spectrum due to non-linearity\, but not all. Whereas\, in principle\, if the forward modelling is done precisely enough no information is lost.\ n\nOf course "done precisely enough" is the crucial phrase and forward mod elling needs to balance precision with speed. The more common summary stat istics methods are usually much\, much faster than forward modelling.\n\nS o\, Natalia presents a new method for evolving non-linearities faster\, on e that in particular does a much better job at capturing under-densities t han the typical particle-mesh codes. She also shows that this forward mode lling technique is able to extract\, statistically\, information about the 3D regions between absorption lines because it uses the full set of (corr elated) initial conditions as its set of model parameters.\n\nTalk video: youtu.be/eBQv5gRs2y8\n\nPaper: [2005.12928] A hierarchical fie ld-level inference approach to reconstruction from sparse Lyman-α forest data\n\n
\n\nIndex to Key Parts of the Talk:\n\n[00:00] Shaun's intro to this forward modelling topic and Natalia's work\n\n[01:19] Natalia's summary of the 2005.12928 paper: inferring the da rk matter distribution from the Lyman-α forest\; improved method introduc es a field-based approach to describe the DM dynamics\, more accurate in d escription of the voids and under-densities\n\n[02:33] Q&A: what are two simple things you'd want viewe rs to remember about this talk?: it's possible to infer 3D information from the Lyman-α forest\, and a field-based approach to describe the DM dynamics has some advantages over the more standard particle-based approac h \n\n[03:54] Q&A: the motiva tion for this work\n\n[06:55] (1) collaborators\, and (2) this work was carried out within the Aqui la Consortium\n\n[07:13] First slide: Forward modelling approach: visual description of the tec hnique\; initial conditons => dynamical model => data model => compare to real data\n\n[09:55] From dat a to cosmology\n\n[11:20] Data model: fluctuating Gunn-Peterson approximation\n\n[14:23] The BORG framework: Gaussian pr ior => dynamical model => data model \n\n[16:15] Propagator Perturbation Theory (PPT): an alternative t o particles: recently developed semiclassical analogue to Lagrangian p erturbation theory (LPT)\n\n[20:53] Comparison LPT and PPT\n\n[22:20] Statistical modular framework\n\n[23:23] Hierarchical annealing with PPT\n\n [24:41] Testing the method w ith mock data\n\n[26:42] Interpolation between lines-of-sight\n\n[27:34] Posterior matter power spectrum\n\n[28:13] Cluster mass profile\n\n[2 8:48] Void profiles: app lication - constraint on total neutrino mass\n\n[29:15] Constraining cosmological parameters\n\n[3 1:14] Velocity field at z > 2\n\n[31:47] Matter flow \n\n[32:12] Summary\ n\n[33:33] Q&A: next steps\n\n[35:06] Q&A: outside o f your own research\, what do you think is the most interesting thing in c osmology at the moment?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Benjamin Giblin (University of Edinburgh) DTSTART:20200711T060000Z DTEND:20200711T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/16 DESCRIPTION:Title: What is KiDS-1000? And why we can trust its results!\nby Benja min Giblin (University of Edinburgh) as part of Cosmology Talks\n\n\nAbstr act\nBen Giblin tells us about the in-process KiDS-1000 results release. A t the time this video is released the collaboration have satisfied themsel ves that their data is robust and passes all relevant consistency checks\, but haven't yet released any cosmological results. \n\nIn fact\, their co smological results are still blinded\, but the consistency remains for all possible unblinded results. So whatever the results are\, they're consist ent.\n\nI'm not an observer\, but I found Ben's discussion of things like "point spread functions" and "shear ratio null tests" to be very clear and understandable - in fact much\, much clearer than what I'm used to from t alks like this 😅.\n\nPaper: [2007.01845] KiDS-1000 catalogue: weak gravitational lensing shear measure ments\n\nPaper on redshift measurements using self organised maps: arxiv.org/abs/1909.09632\n\n\n\nIndex to Key Parts of the Talk:\n\n[00:01] Shaun's intro to the topic and Ben's work\n\n [00:54] Ben's opening comments on this work: series of tests\; modeling of the point spread function \; redshift distributions\; some new findings\n\n[03:01] Q&A: what are two simple things you'd want vie wers to remember about this talk?: (1) the new data release has gone t hrough a lot of rigorous testing and found to be robust\, and (2) don't ju st copy the equations in other papers without proving them to yourself\n\n [03:29] Q&A: what is the moti vation for this work?: measure cosmological parameters from the weak l ensing signal: cosmic shear\, galaxy-galaxy lensing\, and galaxy clusterin g\; the benefits of weak lensing as a low redshift probe in comparison to Planck as a very high redshift probe\n\n[06:13] The details of KiDS-1000 and Ben's recent paper: Ki DS-North and KiDS-South\; improvements on this data since the previous dat a release: photometric redshift calibration\; paper references below are t o the first paper that has come out as of the date of this talk: [2007.01845] KiDS-1000 catalogue: weak g ravitational lensing shear measurements\n\n[08:14] Table comparing 3 surveys: KiDS\, DES\, and HSC< /a>\n\n[08:46] Weak lensing c osmology: the state of play: KiDS measures a lower S8 than the other 2 surveys\; tension between KiDS and Planck ~2.5σ\; comments on other pape rs\; this tension with Planck disappears if KiDS uses COSMOS2015\, which is used by DES and HSC to calibrate their redshifts\; ongoing debate\n\n[1 3:42] KiDS-1000: How to make sure our shear and redshift estimates are accurate: Null tests of the PSF modelling\; Null-tests of the joint shear and redshift data\n\n[14:16] PSF Modelling: the "effe ctive PSF" describes how the light of a point source would spread out due to atmospheric\, telescope\, and camera effects\; the challenge of weak le nsing\; how it's modelled\; comments on Fig. 2 of paper\n\n[18:00] PSF Modelling is hard: details on 3 different prescriptions in the literature\; caution on 2 & 3 potenti ally biasing cosmological inference (e.g.\, S8)\; correlation functions co mments\n\n[23:20] First-orde r PSF Systematics Model\n\n[26:24] Flux/spatial dependent PSF systematics model: accounting fo r imperfections in the CCD chips (section 3.4.1 in paper\, Fig. 4)\n\n[29: 29] PSF modelling takeaways< /a>\n\n[30:08] Tests of the joint shear-redshift data\n\n[30:28] Galaxy-Galaxy Lensing (GGL): how shapes of background gal axies are correlated with positions of foreground lensing galaxies\; typic ally causes a tangential shear pattern\n\n[30:55] Using GGL to detect additive systematics in the shea r: see section 4.2 in paper\, Fig. 10\; a new test that they advocate\ n\n[34:10] GGL to test the j oint shear-redshift measurements\; comments on Fig. 11 of paper\n\n[39 :14] Shear-Redshift Null-Tes t Takeaways\n\n[39:30] M ain Takeaways: 3 points but one wasn't mentioned earlier: this is a ne at example of a blind paper - 3 versions of the data\, one is the true dat a\, other 2 are fake but derived from original data and modified\; see red comments in the paper for blinding details\; cosmological constraints wil l soon be released both from cosmic shear and 3x2pt cosmological analyses\ n\n[42:46] Q&A: Next Steps\n\n[45:00] Q&A: outside o f your own research\, what do you think is the most interesting thing in c osmology at the moment?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/16/ END:VEVENT BEGIN:VEVENT SUMMARY:Simon Birrer (Stanford) DTSTART:20200716T060000Z DTEND:20200716T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/17 DESCRIPTION:Title: TDCOSMO H0 results with more data and fewer approximations\nby Simon Birrer (Stanford) as part of Cosmology Talks\n\n\nAbstract\nSimon t ells us about the strong lensing time delay measurements of the Hubble con stant performed by TDCOSMO. \n\nIn the recent paper he has relaxed assumpt ions about the density profiles around the lenses. Specifically\, in this analysis it is no longer assumed that the density follows a power law\, or NFW profile. This naturally widens the error bars on the measurement beca use the "mass sheet degeneracy" is no longer pinned down.\n\nIn order to p in this degeneracy back down they use kinematic data from the lenses to mo del the density profile. They also calibrate their model on an additional external data set of strong lenses. When using just TDCOSMO lenses the cen tral value stays the same\, but when adding the new "SLACS" lenses\, the m easured value of H0 drops to be almost exactly the same as the Planck valu e. Cat\, meet pigeons.\n\nSimon also goes into what the future will look l ike and what data is needed to bring the accuracy of TDCOSMO back to what it was before these assumptions were relaxed.\n\nSimon: https://sibirrer.g ithub.io/\nThe paper: https://arxiv.org/abs/2007.02941\nThe analysis pipel ine: https://github.com/TDCOSMO/hierarchy_analysis_2020_public\n\n
\n\n Index to Key Parts of the Talk:\n\n00:00 Shaun's introduction\n\n01:23 Simon's opening comments: the key that I want pe ople to take away from this paper is not the numbers themselves but the me thodology and the possibility to add new data\; there is a huge potential on how we can utilize this type of framework to move forward \n\n02:53 Q&A: is there another take away message from this talk that you'd like to mention?\n\n04:44 Time-delay cosmography: equation co mponents\; geometric quantities\; if source is variable\, there is a "time -delay" between the multiple images\; this method provides a physical anch or of the scales at intermediate redshifts\, independent of CMB and distan ce ladder\; delay is from a few days to a few months (110 days is longest in current sample) \n\n06:59 TDCOSMO project: new collaboration of H0LiCOW + STRIDES + SHARP + CO SMOGRAIL projects\; 7 lenses analyzed to date\n\n07:55 Single lens - multiple data: basic ingredien ts: high resolution imaging to measure and describe in detail the distorti on of the lensing effect\; time delay measurements\; stellar kinematics\; line of sight contribution\; different telescopes involved\n\n10:31 Forward modeling in action: rec onstruct lensing phenomena from the imaging data\n\n11:02 Previous results from the H0LiCOW collaborati on: 6 lenses\; blind analysis for all except first\; question on obser ved trend of decreasing H0 with increased redshift\n\n12:57 H0 measurements in flat ΛCDM - performed b lindly\n\n13:59 mass-shee t degeneracy: see Fig. A.1 and section 2 of paper\n\n15:44 TDCOSMO IV: Hierarchical time-delay cos mography - joint inference of the Hubble constant and galaxy density profi les\n\n16:01 Velocity dis persion measurements of the deflector galaxy can break the mass-sheet dege neracy: summary of added data\; Fig. 4 in paper\n\n16:58 Constraining galaxy density profiles with lensing and kinematics: SLACS lenses\; have excellent imaging from HS T and kinematics from BOSS spectra\n\n17:23 Question and discussion on the assumptions\n\n19:02 Returning to discussion on the slides: Fig. 12\, 13b\, 14\, & 17 in paper\n\n26:22 Q&A on details of the modeling\n\n30:29 < a href="https://youtu.be/QrdqbZv_tBs?t=1829">More discussion on the mass-s heet degeneracy slide\n\n33:51 Next steps: Fig. 18 from paper\n\n34:34 Way forward 1: data on time delay lenses\n\n35: 40 Way forward 2: adding ext ernal data sets\n\n36:44 Way forward 3: challenge yourself\n\n38:40 What is the prognosis for TDCOSMO precision?: opti mistic that within a year can get back down to 3% uncertainty\n\n39:07 Q&A: What do you expect will be the resolution to the H0 issue?\n\n40:27 Q&A: outside of your own research\, what do you think is the most interesting thing in cosmology at the moment?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/17/ END:VEVENT BEGIN:VEVENT SUMMARY:Eva-Maria Mueller (Oxford) DTSTART:20200720T060000Z DTEND:20200720T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/18 DESCRIPTION:Title: Even BAO alone requires dark energy + cosmology from the last eBOS S data release\nby Eva-Maria Mueller (Oxford) as part of Cosmology Tal ks\n\n\nAbstract\nEva-Maria tells us about the cosmological results from t he final (cosmology relevant) SDSS/eBOSS data release. eBOSS is a spectros copic galaxy survey\, precisely mapping galaxies\, quasars and the Lyman- α forest.\n\nThe two key probes are baryon acoustic oscillations (BAO) an d redshift space distortions (RSD). BAO acts as a distance ladder\, and eB OSS now has measurements of BAO at enough redshifts that their data alone constrains the expansion history of the universe precisely enough to prove the existence of a dark energy component. The RSD measurements probe the growth of structure\, but are unable to resolve any tension between weak l ensing measurements and the CMB\, with their results lying right between t he two alternatives\, consistent with both.\n\nThe distance scale in BAO c an also be anchored using constraints from big bang nucleosynthesis (BBN) allowing eBOSS to infer the expansion rate of the universe today without r eference to the CMB. Their measurement is consistent with the CMB and inco nsistent with the local distance ladder measurements (e.g. SH0ESS).\n\nThe BAO\, RSD and CMB are all consistent with the time evolution of the (unan chored) supernovae so all these data sets can be combined to give an overa ll constraint. This gives very tight bounds on any deviations from a cosmo logical constant in ΛCDM\, and on any deviations from a flat geometry wit hin our observable universe.\n\nThe next stage in spectroscopic surveys is DESI\, and then Euclid. COVID permitting\, we should have the first resul ts from DESI within three years.\n\nEva-Maria's Oxford page \n\nThe paper: [2007.08991]The Completed SDSS-IV e BOSS: Cosmological Implications from two Decades of Spectroscopic Surveys at the Apache Point observatory\n\n
\n\nIndex to Key Parts of th e Talk:\n\n00:00 Shaun's introduction\n\n00:37 Eva-Maria's opening comments on the paper\n\n01:28 Q&A: what are two simple things you'd want v iewers to remember about this talk?\n\n03:24 1st slide: Cosmological results from 20 years of SDSS redshift surveys: different SDSS components\n\n05:31 Sky coverage of eBOSS: all of the data was taken with the 2.5m Sloan Telescope in the Apache Point Observatory in Ne x Mexico\n\n06:18 What BAO is and how it's being using: 1st main observable\; a preferred scale in the clustering and distribution of galaxies that can be used as a standard ruler\n\n06:43 Redshift-Spac e Distortions: 2nd main observable\; gives the growth rate of structur e and is sensitive to the theory of gravity \n\n07:31 A journey of firsts: SDSS made 1st detection of BAO signal in 2005\; BAO bump\n\n08:11 BOSS had 1st detection of the BAO signal in the distribution of neutral hydrogen from LyA forest in 2013: also in the distribution of quasars in 2017\n\n08:28 Q &A discussion on the size and location of the peak: template fitting\n \n08:58 SDSS BAO Distance Lad der\n\n09:47 The growth o f structure: comparison with Planck 2018 ΛCDM best-fit model\n\n10:26 The 23-paper release: th is talk focused on what is learned about expansion of universe\, curvature \, mass of neutrinos\, taking the measurements and transforming them into constraints of cosmological parameters\n\n11:12 Dark Energy: Takeaway - a significant detection of DE with only BAO data\n\n13:07 Curvature: CMB by itself has large degeneracy between curvature and matter\; adding SN gives improvement but still can't tell for sure\; can n ail it down by adding BAO\, shows to high precision the universe is flat \ n\n14:09 What is the nature o f Dark Energy?: combining different data sets supports the flat ΛCDM model with constant DE \n\n16:21 Hubble Parameter Tension\n\n17:03 Summary diagrams\, step-by-step going through the different contours\n\n18:49 Combin ation of BAO+BBN breaks degeneracy compared to BAO by itself: clear te nsion with distance ladder H0 measurement\; BAO+BBN (using no CMB info) in good agreement with CMB\n\n19:48 allowing DE EoS to vary and combining CMB+BAO+SN (inverse distance l adder) gives H0 in agreement with CMB by itself: DE is not an explanat ion for H0 tension\n\n21:35 Can rephrase H0 tension as a sound horizon tension\n\n23:14 The BAO analysis is robust: hard t o come up with a systematic that would coherently move galaxies in a way t hat wouldn't move the position of the BAO bump\n\n23:50 sigma8 - Omega_m Discrepancy: Fig. 9a in p aper\; results just from RSD\n\n25:52 Comparing full data sets - SDSS\, DES\, Planck\n\n26:59 Constraint on sum of the neutrin o masses: Fig. 13 in paper\; Planck + BAO + RSD + SN constraints is ri ght at minimum edge for IH but not significant enough to rule out IH (thou gh IH becoming less and less likely\; more data needed)\n\n29:47 20 years of cosmology: summary of galaxy spectroscopic surveys\; Fig. 14 in paper\n\n31:50 Conclusion: Legacy of BOSS/eBOSS\n\n32:5 5 Q&A: Is it valid to combin e SN with BAO and CMB?\n\n34:53 Q&A: Where to next? What is coming with Stage IV?: DESI and Eu clid for spectroscopy\; other things DESI can look at\; CMB-S4\; LSST (Ver a C. Rubin Observatory)\n\n38:38 Q&A: outside of your own research\, what do you think is the most int eresting thing in cosmology at the moment?\n\nSupplemental info: One-page s ummary of the cosmology results and implications at the SDSS website\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/18/ END:VEVENT BEGIN:VEVENT SUMMARY:Simone Aiola (Flatiron CCA and Simons Observatory\, Atacama) DTSTART:20200805T060000Z DTEND:20200805T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/19 DESCRIPTION:Title: ACT+WMAP is as powerful as Planck\; CMB results on ΛCDM are robus t\nby Simone Aiola (Flatiron CCA and Simons Observatory\, Atacama) as part of Cosmology Talks\n\n\nAbstract\nSimone talks about the latest Ataca ma Cosmology Telescope cosmology paper(s). He goes into detail at the begi nning about the history of ACT and where it is now\, as well as what data was in the latest results. \n\nHe then goes into how the data has been che cked for robustness and how it is sufficiently consistent with WMAP to mot ivate combining the two data sets (i.e. WMAP for the large scales and ACT for the small scales and polarisation). Combined\, WMAP and ACT are as con straining as Planck\, but don't add much additional constraining power whe n added to Planck (they do measure the same sky of course!).\n\nThe ACT po larisation data is sufficiently high in signal to noise that you can even make maps of the data that look as clear as the Planck/WMAP temperature ma ps\, which is quite stunning.\n\nThen Simone goes into the final cosmologi cal results. Overall\, Planck and WMAP+ACT are mostly consistent. In parti cular\, their H0 predictions are very similar. There is a small amount of tension that manifests as a different value of the spectral index (or\, mo re precisely\, in the ns vs omega_b constraint contours). This is only ~2. 4 sigma\, so worth keeping an eye on\, but not worth getting too excited a bout yet.\n\nPapers: arxiv.org/ abs/2007.07288 and arxiv.or g/abs/2007.07289\n\nData: lambda.gsfc.nasa.gov/product/act/actpol_prod_ table.cfm\n\n
\n\nIndex to Key Parts of the Talk:\n\n00:00 < a href="https://youtu.be/Ememq6FnN1U">Shaun's introduction\n\n00:37 Simone's opening comments\n\ n01:15 Q&A: what are two simpl e things you'd want viewers to remember about this talk?: combining WM AP large-scale and ACT small-scale data yields cosmological constraints at a precision comparable to Planck\; provides a ΛCDM cross-check independe nt of Planck\; Planck and ACT systematics likely very different\; results found to be in agreement \n\n02:43 Q&A: what is interesting about ACT that we couldn't just get from Pl anck?: CMB secondaries and foregrounds are not possible to do with sma ller telescopes\n\n04:05 Brie f comments highlighting the ACT Collaboration\n\n04:42 Some details on the ACT telescope: plot showing ACT's resolution and sky area coverage compared to other CMB missi ons\n\n05:46 ACT Datasets : a brief overview of past\, current\, and future ACT datasets\; results p resented here are based on ACTPol data taken from 2013-2016\; ACTPol measu red polarization\, previous ACT versions did not\; ACT to continue observi ng through 2021\n\n06:46 Deta ils on the 3 cameras: cross-checks ability - slightly different optics \, different locations in the telescope\; data recorded at 98 and 150 GHz\ n\n07:39 Q&A on removing fore grounds: higher frequency data from Planck used for detecting any dust contamination\, though it has no CMB component\; foreground contamination is small compared to CMB signal at the frequencies used by ACT\n\n09:19 < a href="https://youtu.be/Ememq6FnN1U?t=559">Shaun's post-recording edit wi th additional unrecorded comments by Simone about foreground removal\n \n10:23 ACT DR4 Survey: t otal map-depth varies across the sky\; noise levels compared to Planck\; F ig. 4 (top panel) in 2007.07288\n\n11:32 ACT temperature and E-mode polarization maps at z~1100: tw o different points of view of the physics of the last scattering surface\; comparison with Planck measurements at different scales from ACT\n\n15:22 Regions for power spectra: depth of the map variable across the sky\; "deep" and "wide" (shallower ) regions\; effective area\; Fig. 2\; NOTE: Figure references are for 2007.07289 unless otherwise indicated\n\n17:53 Power spectra at 98 & 150 GHz: deep vs wide plo ts\; Fig. 10\n\n20:16 CMB-on ly power spectra: wide patch errors bars on intermediate scales are sm aller than for deep (especially visible in EE)\, whereas the deep does wel l in constraining foregrounds\; Figs. 15 and 24\n\n21:54 Parameter-level tests: Fig. 14\; some of the cosmological parameters are being constrained better by TE than TT\; no evidence of systematic effects\n\n23:49 ACT DR4 Cosmology: triangular plot comparing WMAP\, Pla nck\, ACT in 5D parameter space (all 3 have a τ prior in common)\, Fig. 1 2 in 2007.07288\; ACT vs WMAP/Planck consistent at 2.3-2.7σ\; two expecte d degeneracies \n\n26:48 Co mbining ACT+WMAP (baseline) and ACT+Planck: ACT+WMAP breaks some of de generacies that are in the 2 data sets independently\; Figs. 17 & 19 in 20 07.07288\; ACT shows a mild preference for less damping in the small-scal e power spectrum than in ΛCDM\; for more info on combining ACT+WMAP\, see section 6.2.2 in 2007.07288\n\n30:51 ACT DR4 H0 Estimate: Fig. 18 in 2007.07288\n\n31:30 ACT DR4 Cosmology beyond ΛCDM: Figs. 20\, 21\, 22 in 2007.07288\n\n32:53 A_lens finding (consistent with unity) and discussion: F ig. 20 in 2007.07288\; also see section 7.1.1 in 2007.07288\n\n36:20 ACT\, WMAP\, Planck: Figs. 14 \, 15 in 2007.07288\; ACT prefers a 2.4σ lower first peak in TT\, higher TE\, lower EE\n\n40:02 ACT D R4 Publicly Released: ~0.5TB of data products and 4.5TB of simulations available at lambda.gsfc.nasa.gov\n\n40:18 Q&A: What comes next?\n\n42:44 Simons Observatory discussion\n\n43:41 Q&A: outside of your own research \, what do you think is the most interesting thing in cosmology at the mom ent?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/19/ END:VEVENT BEGIN:VEVENT SUMMARY:Marika Asgari (University of Edinburgh) DTSTART:20200921T060000Z DTEND:20200921T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/20 DESCRIPTION:Title: KiDS 1000 is statistics dominated and in 3σ tension with Planck c osmology\nby Marika Asgari (University of Edinburgh) as part of Cosmol ogy Talks\n\n\nAbstract\nMarika tells us about the recent Kilo Degree Surv ey (KiDS) cosmological results. These are the first results from KiDS afte r they have reached 1000 square degrees.\n\nMarika first explains how they know that the results are "statistics dominated" and not "systematics dom inated"\, meaning that the dominant uncertainty comes from statistical err ors\, not systematic ones. \n\nShe then presents the cosmological results\ , which primarily constrain the clumpiness of matter in the universe\, and which therefore constrain Ω_m and σ_8. In the combined parameter "S_8"\ , which is constrained almost independently from Ω_m by their data they s ee a more than 3σ tension with the equivalent parameter one would infer f rom Planck.\n\nMarika's website: http s://www.roe.ac.uk/~ma/\n\nPapers: 2007.15632 and 2007. 15633\n\nKiDS web inar\n\n
\n\nIndex to Key Parts of the Talk:\n\n00:00 Shaun's introduction\n\n00:40 Marika's opening comments about t wo of the five recent KiDS papers: also see the KiDS Key Facts segment beginning at 10:39\n\n01:24 Q &A: what are two things you'd want viewers to remember about this talk?\n\n02:13 Q&A: what was the motivation for this work?: the strength of cosmic shear in general is that it rather directly measures the amount of matter compared to surveys that use galaxy positions\; KiDS is a unique survey in that there's a good handle on the systematics\; also see segment starting at 08:50\n\n03:12 < a href="https://youtu.be/-o-u7A4QAyE?t=192">Q&A: What was done and what ar e the results? \n\n04:20 Cosmic shear 101 \n\n06:47 Modeling \n\n07:47 Blin ding \n\n08:50 Standard c osmological model \n\n10:39 KiDS: Key Facts \n\n11:32 Results: comments on Fig. 5: (all figure references are to 2007.15 633 until discussion on the 2nd paper begins at 27:17)\n\n13:01 Two point statistics and their scale se nsitivity\n\n13:40 Commen ts on the 4 panels of Fig. 1 from 2007.15633\n\n17:39 "Headline plot"\, comments on Fig. 6\n\n 19:08 The capital S8 paramet er\n\n21:00 Impact of nu isance parameters: comments on Fig. 7\n\n25:40 Comparison with Planck\, DES\, and HSC: comment s on Fig. 9\n\n27:17 Start o f discussion on 2nd paper\, 2007.15632All following Figure references from here are for 2007.15632)\n\n27:55 Survey Footprint \n\n28:30 Figure 1: 3x2pt: Cosmic Shear +\n\n29:15 Figure 2: 3x2pt: Cosmic Shear + Clustering +\n\n29:55 Figure 3\, le ft panel: 3x2pt: Cosmic Shear + Clustering + Galaxy-Galaxy Lensing\n\ n32:47 Figure 6\, right pane l: Consistency between probes\n\n33:37 Figure 4\, KiDS - Planck Tension Metrics\n\n35:27 Figure 8\, Comparison with other analyses\n\n36:10 Compar ison of KiDS core cosmology papers\n\n37:13 Q&A: What's the next big thing in photometric lensing after what's currently happening?\n\n38:44 Q&A: What are you working on next?\n\n39:18 Q&A: outside of your own research\, what do you think is the most interesting thing in cosmology at the momen t?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/20/ END:VEVENT BEGIN:VEVENT SUMMARY:Bodo Schwabe and Mateja Gosenca (Göttingen U and U of Auckland) DTSTART:20200929T050000Z DTEND:20200929T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/21 DESCRIPTION:Title: AxioNyx - Public code to simulate both Fuzzy and Cold Dark Matter in hires | FDM≡CDM on large scales\nby Bodo Schwabe and Mateja Gosen ca (Göttingen U and U of Auckland) as part of Cosmology Talks\n\n\nAbstra ct\nBodo Schwabe and Mateja Gosenca tell us about AxioNyx\, which is a new public code for simulating both Ultralight (or "Fuzzy") dark matter (FDM) and Cold dark matter (CDM) simultaneously. The code simulates the FDM usi ng adaptive mesh refinement and the CDM using N-body particles. As far as I'm aware it is the first publicly available code that can do both without needing adaptation out of the tin (let me know in the YouTube page commen ts if I'm missing any codes - sorry :-/ ).\n\nThe code passes a bunch of s anity/consistency checks\, matching linear theory when it should match and deviating when it should deviate. The paper discussed mainly just introdu ces AxioNyx\; the new physics will come in future papers. Things Bodo\, Ma teja and collaborators will be tackling are: simulations with full cosmolo gical initial conditions for the combination of FDM+CDM\, adding baryons ( long-term project)\, gravitational heating of stars in FDM halos\, and re- assessment of earlier constraints on FDM with FDM now only a sub-fraction of the total dark matter content (e.g. the Lyman Alpha constraints). Stay tuned\, and/or get in touch with them if you're keen to help make any of t hat happen :-).\n\nOne neat result from this paper was the confirmation of the "Schrodinger-Vlasov" correspondence. This essentially says that FDM a nd CDM will behave equivalently on large enough scales. On smaller scales the fuzziness of the FDM causes it to deviate (essentially\, it is so ligh t that its deBroglie wavelength is astrophysically relevant). This corresp ondence has been shown statistically\, and as a limiting result\, in earli er papers but this is (as far as I'm aware) the first paper where the FDM and CDM are in the same gravitational potentials in the same simulation an d one can see them do the same stuff on large scales. It wasn't surprising \, but it's still good to check and see it happen. \n\nThe most interestin g things happen when the proportions of FDM and CDM are similar (i.e. when one doesn't just dominate the other entirely)\, which might be an interes ting thing for considering in future papers too.\n\nBodo: https://bodoschwabe.github.io/
\nMateja: < a href="https://uk.linkedin.com/in/mateja-gosenca-99b267133">https://uk.li nkedin.com/in/mateja-gosenca-99b267133\n\nAxioNyx: https://github.com/axionyx
\nThe paper: https://arxiv.org/abs/2007.08256\n\n\nIndex to Key Parts of the Talk:
\n00:00 Shaun introduces Bodo Schwabe and Mateja Gosenca< /a>
\n\n00:37 Mateja'\;s opening comments about this new code
\n\n02:18 Q&\;A: what are two things you'\;d want vi ewers to remember about this talk?
\n\n03:41 Q&\;A: what was the motivation for this work?
\n\n06:36 Q&\;A: What was done in the paper? What are the details about adaptive mesh refinemen t (AMR)?
\n\n07:05 Sli de: FDM Structure Formation
\n\n09:17 Q&\;A: Is there an intuitive way of explaining why the Schrodinger equation is the right equation here?
\n\n10:10 Slide: FDM mass constraints
\n \n14:49 Slide: Quantifying Mi xed Fuzzy Cold Dark Matter Halo Dynamics: Radial density profiles\; CD M velocity dispersion vs FDM granular structure\; Solitonic core dynamics< br>\n\n16:22 Slide: AxioNyx: Simulating Mixed Fuzzy and Cold Dark Matter: Figure 1 from the paper\n\n17:54 Slide: Spherical Collapse – linear: Figures 2 and 3 from the paper
\n\n21:14 Slide: Spherical Collapse – No n-linear: Figure 4 from the paper
\n\n27:26 Slide: Comments on Figures 5\, 6\, and 7 from the p aper
\n\n32:07 Q&\ ;A about (1) the linearity and (2) is there an intuitive explanation of th e equations?
\n\n35:30 Conclusions slide
\n\n38:22 Q&\;A: What is coming next in your work?
\n\n42:29 Q&\;A asked individually to B odo and Mateja: outside of your own research\, what do you think is the mo st interesting thing in cosmology at the moment?
\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/21/ END:VEVENT BEGIN:VEVENT SUMMARY:Ryan Keeley (Korea Astronomy and Space Science Institute) DTSTART:20201008T050000Z DTEND:20201008T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/22 DESCRIPTION:Title: Maybe inflation is the solution to the Hubble tension!?\nby Ry an Keeley (Korea Astronomy and Space Science Institute) as part of Cosmolo gy Talks\n\n\nAbstract\nRyan tells us about how the Hubble tension (betwee n Planck measurements of the cosmic microwave background temperature aniso tropies and SH0ES measurements of the expansion rate of the universe) can be completely solved with a non-standard primordial power spectrum for the curvature perturbation\, which could arise e.g. if there is a kink in the inflationary potential. \n\nThe non-standard power spectrum has an oscill atory feature that exactly mimics the effects of a slightly different valu e for the expansion rate today. They find this power spectrum by explicitl y reconstructing it\, so they aren't supplying a well motivated a priori m odel. However their work does represent a proof of concept that a non-stan dard power spectrum could mimic the effects of a different expansion rate. \n\nWhile the Hubble tension remains unsolved and while all other models t o explain it suffer from their own problems\, work like this remains well motivated. It would perhaps be a bit fine tuned to have a feature at exact ly the right place in the primordial power spectrum to mimic the effects o f H0 today\, but there could be many features and if one happened to align then this would be what we would see\, so it can't be ruled out a priori. \n\nFuture work will test this with polarisation data and the matter power spectrum... so stay tuned. If this is the solution it might leave measura ble signatures in those results.\n\nRyan: http://cosmology.kasi.re.kr/memb ers.php?member=ryan \n\nThe paper: https://arxiv.org/abs/2006.12710 Inflat ion Wars: A New Hope\n
\n\nIndex to Key Parts of the Talk: \n\n 00:00 Shaun's introduction\ n\n01:04 Ryan's opening commen ts\n\n02:01 What two simp le things do you want people to take away from this talk?\n\n02:35 What is the background for this work?\n\n03:36 Deconvolut ion slide: decomposition is done with the modified Richardson-Lucy dec onvolution algorithm\n\n04:19 The transfer function and how it gives the modified initial power spectru m\n\n06:47 Modified Richa rdson-Lucy Deconvolution slide\n\n07:43 Sound Cancellation slide: Figure 1 from the paper\n\n09 :22 Features slide: Figur e 2 bottom panel\n\n10:20 Pos teriors slide: Figure 3\n\n13:41 Priors slide\n\n18:08 Filtering slide: Figure 4\n\n23:59 Conclusions slide\n\n24:45 Where to next?\n\n26:42 Outside of your own research\, what do you think is th e most interesting thing in cosmology at the moment?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/22/ END:VEVENT BEGIN:VEVENT SUMMARY:George Zahariade (Arizona State University) DTSTART:20201108T050000Z DTEND:20201108T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/23 DESCRIPTION:Title: Quantum gravity adds (v quiet) noise to gravitational wave detecto rs\nby George Zahariade (Arizona State University) as part of Cosmolog y Talks\n\n\nAbstract\nGeorge tells us what happens in gravitational wave detectors when you quantise the gravitational field.\n\nHe talks about a c alculation he did with Maulik Parikh and Frank Wilczek which examines what effect quantising the gravitational field would have on gravitational wav e detectors.\n\nThey first treat the detector and gravitational field quan tum mechanically. For certain gravitational wave states (e.g. a coherent s tate\, a squeezed state and a thermal state) they are then able to solve t he gravitational field parts of the resulting path integral (or canonical expectation values).\n\nIn the resulting expression they then take the mos t probable path for the detector (i.e. the classical path) and determine a n equation of motion for the distance between the ends of the detector (i. e. the classical equation of motion for the detector\, with quantum effect s from the gravitational field included).\n\nThis new equation of motion i s like the purely classical one except with the addition of a new noise te rm. In the case of a squeezed state this noise can be exponentially enhanc ed\, which might have implications for gravitational waves from inflation\ , which at least start out in a squeezed state.\n\nGeorge: linkedin.com/george-zahar iade
\nPapers: 2010.0820 8 and 2010.08205
\nE ssay: 2005.07211\n
\n\n< b>Index to Key Parts of the Talk: \n\n00:00 Shaun's introduction : This is on how one might measure the quantum nature of gravitational wav es. Being a bit outside the realm of normal cosmology\, it's at a general technical level so this talk will be at maybe a colloquium level rather th an a seminar level. \n\n00:42 George's opening comments \n\n04:44 Q&A: what are two things you'd want viewers to remember about this talk?: (1) we pre dict that the quantization of the gravitational field should imply the exi stence of an additional source of noise that would superimpose itself to a ll the other noise sources that exist in a GW interferometer\, and (2) the characteristic of this noise depends strongly on the quantum state of the gravitational field\, so the noise it induces on the signal (depending on its state) will be very different and possibly observable.\n\n06:03 Q&A: what was the m otivation for this work? \n\n06:50 Q&A: Why hasn't this calculation been done before ? \n\n08:53 Could LIGO do something differently now or in the future that would be useful to test this prediction?: the signature of the quantization of the gravitational field is a noise term\, so we need an experiment that f ocuses on the noises not on the signals. \n\n09:11 Getting into the details: First s lide - the history of this topic and references\n\n10:00 Outline of the presentation \n\n10:54 Ba sic Idea slide \n\n13:54 Detector Model \n\n16:00 Assumptions and approximations \n\n21 :28 Detector response to quantized GW \n\n23:21 Calculating the transition probability from the initial states to the final state \n\n24:15 Influence Functional slide: basic ally this functional encodes all the quantum effects of the gravitational field \n\n25:46 Able to calculate the influence function for different incoming gravit ational field states: first consider a coherent state \n\n29:16 Analysis of the I nfluence Functional slide (for a coherent state) \n\n32:05 Back to the Transition Probability slide \n\n33:18 Langevin Equation slide: final result - effective equation of motion for the detector including quantum effects\; the quantu m modification of the classical geodesic deviation equation\n\n36:07 Analysis of Noise slide: for different states there will be different spectra of the noi se - equations for vacuum and coherent states\, thermal states\, and squee zed states\; thermal states might be of interest to cosmologists (some sto chastic GW backgrounds might be thermal)\; squeezed states of the gravitat ional fied can arise from cosmology (inflationary perturbations) \n\n41:07 Estimates of the noise for each case: the most hopeful scenario is the case of squ eezed gravity states that might have a quantum noise that is measurable \ n\n42:39 Summ ary slide \n\n45:08 Q&A: Where to next? \n\n46:15 Q&A: outside of your own research\, what do you think is the most interesting thing in cosmology at the moment?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/23/ END:VEVENT BEGIN:VEVENT SUMMARY:Moritz Haslbauer and Indranil Banik (University of Bonn) DTSTART:20201118T050000Z DTEND:20201118T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/24 DESCRIPTION:Title: Maybe Milgromian gravity solves the Hubble tension!? - The KBC voi d & νHDM model\nby Moritz Haslbauer and Indranil Banik (University of Bonn) as part of Cosmology Talks\n\n\nAbstract\nMoritz Haslbauer and Indr anil Banik talk about the Keenan\, Barger and Cowie (KBC) void and the νH DM model of cosmology. \n\nThe KBC void is a locally observed ~300 Mpc sca le under-density that appears to be impossible within ΛCDM (under-densiti es shouldn't have emptied out this much by now).\n\nνHDM is a model that has sterile neutrinos as a hot dark matter component and enhanced gravity in environments with a weak gravitational field. This dark matter adequate ly explains the CMB and expansion history of the universe\, but doesn't cl uster on the smallest scales. The modified gravity (essentially Milgromian dynamics\, or MOND) then kicks in on these scales to produce phenomena li ke the correct rotation curves in galaxies.\n\nMoritz and Indranil give an intro to both KBC and νHDM\, and then explain how this model is consiste nt with the main tent-poles of modern cosmology (e.g. the CMB anisotropies \, nucleosynthesis\, the displacement of the gas and weak lensing in the b ullet cluster\, galaxy rotation curves\, the clustering of galaxies) and c an also alleviate some of the tensions in the standard ΛCDM model.\n\nThe paper: 2009.11292 \n\nMori tz: moritzhaslbauer.jimdo free.com \n\nIndranil: Youtube videos \n\nA blog post by Indranil\, Mori tz (and co-author Pavel) on the same topic: Big Trouble in a Deep Void\n\nA blog with ongoing updates of the most serious problems for standard cosmology: The Dark Matt er Crisis\n
\n\nIndex to Key Parts of the Talk:\n\n[00:00] < a href="https://youtu.be/LMhjenB7V8g?t=0">Shaun's intro\n\n[00:42] Opening comments (Moritz)\n\n [00:58] Brief summary of findi ngs Overview: Keenan-Barger-Cowie void and H_0 tension\n\n[03:36] Take Home Message slide\n\n[ 04:08] The observations that motivated this project (Indranil)\n\n[04:34] The most important references and observational constr aints\n\n[06:00] The KBC void and Hubble tension in ΛCDM: the Millennium (MXXL) simulation\n\n [09:18] Comments on Figure 1 from the paper\n\n[09:46] Why an allowance is needed for redshift space distortion effects\n\n[ 10:46] One of the important r esults is the KBC void falsifies ΛCDM at 6.04σ\n\n[10:59] The redshift space distortion is relate d to the impact the void has on the locally measured H_0\n\n[11:56] Observations indicate a deeper underdensity and larger H_0 than is expected in ΛCDM: Figure 2\n\n[13 :22] Large scale failure of ΛCDM: to get from z=1100 to z=0 observations\, need effectively stron ger gravity to grow structure faster\n\n[14:20] Constraints from data on galaxy scales: the second moti vation for this work\n\n[16:04] Milgromian Dynamics (MOND)\n\n[20:42] Cosmological MOND framework (vHDM): Overview\n\n[ 23:14] vHDM framework: Impac t on CMB\n\n[27:31] Terr estrial Evidence for Sterile Neutrinos\n\n[28:58] Astronomical Evidence for Fast Collisionless Mat ter\n\n[32:28] What the vHDM Framework Can Explain\n\n[34:50] Application to KBC void: Model assumptions (Moritz)\n\n[ 36:23] Results: Growth of st ructure: Figure 5\n\n[39:15] Results: Local H_0 & acceleration parameter: Figure 6\n\n[43:15] Results: Peculiar velocity f ield: Figure 8\n\n[45:37] Results: comparing ΛCDM with νHDM \n\n[48:10] Summary and Conclusions\n\n[50:03] What are the next steps? => Outlook s lide\; simulation videos\n\n[51:14] Q&A on why results from many other void studies aren't getting large conflicts with ΛCDM\n\n[53:06] Q&A: outside of your own research what do you think is the most interesting thing in cosmology at the moment?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/24/ END:VEVENT BEGIN:VEVENT SUMMARY:Eiichiro Komatsu and Yuto Minami (Max Planck Institute Garching an d KEK Japan) DTSTART:20201123T050000Z DTEND:20201123T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/25 DESCRIPTION:Title: A tantalising hint of parity violation in the cosmic microwave bac kground\nby Eiichiro Komatsu and Yuto Minami (Max Planck Institute Gar ching and KEK Japan) as part of Cosmology Talks\n\n\nAbstract\nEiichiro Ko matsu and Yuto Minami talk about their recent work\, first devising a way to extract a parity violating signature in the cosmic microwave background (i.e. birefringence) and then measuring it in Planck 2018 data.\n\nThey g et a 2.4 sigma hint of a result\, which is "important\, if true".\n\nThis signal is measured via correlation of E mode and B mode polarisation in th e CMB. If the universe is birefringent then E mode polarisation would chan ge into B mode and there would be a non-zero correlation between the two m easured modes. Unfortunately\, if the detector angle on the telescope wasn 't calibrated perfectly this would mimic the interesting signal. Yuto and Eiichiro's new method is to measure this detector angle by looking at the E-B correlation in the foregrounds\, where the light hasn't travelled far enough to be affected by any potential birefringence in the universe.\n\nT his allows them to partially distinguish between the two types of measured E-B correlation. And with this method they get the hint of a signal for t he new physics in the Planck 2018 data.\n\nThe method can be applied to th e data from all other telescopes that have measured the polarisation of th e microwave background and can therefore be confirmed\, ruled out\, or at least examined by SPT\, ACT\, Polarbear\, etc. \n\nYuto and Eiichiro are a lso working with Planck to see if they can further rule out other systemat ics\, e.g. an intrinsic E-B correlation in the foreground polarisation.\n\ nThe paper: 2011.11254 on the a rXiv and published in PRL.\n\nVideo of talk\n\nEiichiro: https://wwwmpa.mpa-garching.mpg.de/~koma tsu/\n\nYuto: https:// orcid.org/0000-0003-2176-8089\n\n
\n\nIndex to Key Parts of the Talk:\n\n[00:00] Shaun's in tro\n\n[00:38] Opening com ments about the paper by Eiichiro\n\n[01:51] Q&A: What two things would you want people to remember about this talk?\n\n[03:30] The methodology papers that led to this announcement: they have be en working on this for ~2 years\n\n[04:18] How does the electromagnetic wave of the CMB reach us?\n \n[04:41] Cosmic Birefringenc e\n\n[09:24] What was the motivation for this work? Why study cosmic birefringence?\n\n[10:17] E- and B-mode decomposition o f linear polarisation\n\n[10:53] Parity flip\n\n[11:30] Power spectra\n\n[12:05] EB correlation from the cosmic birefringence\n\n[14:46] Searching for the birefringence: Impr ovement #1 (Zhao et al. 2015)\n\n[15:15] The biggest problem: miscalibration of detectors. Impact o f miscalibration of polarisation angles.\n\n[16:10] The past measurements: Uncertainty in the c alibration of α has been the major limitation.\n\n[18:07] The Key Idea: The polarised Galactic foregr ound emission as a calibrator: it would not be affected by the cosmic birefringence\n\n[18:35] Sea rching for the birefringence: Improvement #2 (Minami et al. 2019): Ide a: miscalibration of the polarisation angle α rotates both the foreground and CMB\, but β affects only the CMB. Key: no explicit modeling of the f oreground EE and BB is necessary.\n\n[20:06] Assumption for the baseline result: What about the in trinsic EB correlation of the foreground emission?\n\n[20:57] Likelihood for the simplest case: single -frequency\, full sky data\n\n[21:08] How does it work? Simulation of future CMB data (LiteBIRD)\n\n[23:18] Question that provides an idea for possible follow-up research\n\n[24:20] Application to the Planck Data (PR3): (information for experts)\n\n[25:21] Validation by FFP10 (Planck team's "Full Focal Plane Simulati on")\n\n[25:55] Main Res ults: Figure 1 from the paper\n\n[27:12] Can we see β = 0.35 +/- 0.14 deg by eyes?: Figure 2\ n\n[30:00] How about the foregro und EB?\n\n[32:31] Q&A: if it turns out to be a systematic error\, what is the most likely error s ource?\n\n[33:14] Implic ations: what does it mean for models of dark matter and energy?\n\n[34 :19] Conclusion\n\n[38:4 3] Comment by Yuto on compar ison with Planck data\n\n[39:00] What comes next?\n\n[39:56] Q&A: outside of your own research what do you think is the mo st interesting thing in cosmology at the moment?: Yuto at 40:04 and Eiichiro at 40.13.\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/25/ END:VEVENT BEGIN:VEVENT SUMMARY:Alvaro Pozo (University of the Basque Country) DTSTART:20210213T050000Z DTEND:20210213T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/26 DESCRIPTION:Title: Potential evidence for wave dark matter (via core-halo transition in dwarf galaxies)\nby Alvaro Pozo (University of the Basque Country) as part of Cosmology Talks\n\n\nAbstract\nAlvaro tells us about a recent p aper where he an collaborators detect the transition between a core (flat density profile) and halo (power law density profile) in dwarf galaxies.\n \nThe full core + halo profile matches very closely what is expected in wa ve/ultralight/fuzzy/axionic dark matter simulations (without baryonic effe cts included). That is\, there is a very flat core\, which then drops off suddenly and then flattens off to a decaying power-law profile. The core m atches the soliton expected in wave dark matter and the halo matches an ou ter NFW profile expected outside the soliton.\n\nThey also detect evidence for tidal stripping of the matter in the galaxies. The galaxies closer to the centre of the milky way have their transition point between core and halo happen at smaller densities (despite the core density itself not bein g systematically smaller). The transition also appears to happen closer to the centre of the galaxy\, which matches simulations.\n\nOf course the co re-+halo pattern they have clearly observed might be due to something else \, but the match between wave dark matter simulations and observations is impressive.\n\nThe huge caveat is that the mass for the dark matter that t hey use is very small and in significant tension with Lyman Alpha constrai nts for wave-like dark matter. This might indicate that the source of this universal core+halo pattern they're observing comes from something else\, or it might indicate that the wave dark matter is more complicated than v anilla models... \n\nStay tuned to the arXiv for future papers looking at this in more detail!\n\nPaper: 2010.10337\n
\n\nIndex to Key Parts of the Talk:\n\n[00:00] Shaun's intro\n\n[00:38] Alvaro's opening remarks and bri ef summary of paper\n\n[00:48] Q&A: What two things would you want people to remember about this tal k?\n\n[01:12] Abstract and Introduction\; main objectives of this work\n\n[02:58] Focus on dwarf galaxies\n\n[04:52] Main Two Results\n\n[06:55] < a href="https://youtu.be/HeARhCr0Wr0?t=415">Context - general info of dwar f galaxies and classification between isolated and orbiting galaxies\; Tab le 1 from the 2010.10337 paper\n\n[09:00] Motivation for this work\n\n[12:03] Context: NFW inefficient to describe the densi ty profile in the centre -> solution: add wave dark matter profile\; Plumm er model\n\n[14:28] Metho dology\n\n[19:17] Explan atory comment insert from Shaun while editing\n\n[21:02] Results\; Figure 5 from the paper\n\n [24:06] Figure 1 from the pa per\n\n[24:58] Figure 2< /a>\n\n[28:12] Figure 3: "th e most important\, or one of the most important plots of the paper"\n\ n[31:38] Figure 4\n\n[36 :47] Conclusions\n\n[41: 08] Where to next?\n\n[4 2:49] Outside of your own re search what do you think are the most interesting things in cosmology at t he moment?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/26/ END:VEVENT BEGIN:VEVENT SUMMARY:Volker Springel (Max Planck Institute for Astrophysics) DTSTART:20210226T050000Z DTEND:20210226T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/27 DESCRIPTION:Title: Simulating cosmic structure formation with the GADGET-4 code\n by Volker Springel (Max Planck Institute for Astrophysics) as part of Cosm ology Talks\n\n\nAbstract\nCosmology Talks moderator Shaun Hotchkiss welco mes guest speaker Volker Springel\, who talks about the new GADGET-4 code. \n\nFeaturing all the things you wanted to know about GADGET-4 but were af raid to ask\, including:\n\n- What new algorithms are used to make it bett er and faster than earlier versions\n\n- Why you never heard of GADGET-3\n \n- What new features you can now use when running cosmological simulation s (e.g. varying the algorithms\; or outputting lightcones\, halo catalogue s and merger trees "on the fly")\n\n- why storing the locations of your si mulation particles as integers is better than storing them as floating poi nt numbers\n\n- and what the author of the most used simulation code in co smology thinks are the most interesting questions in cosmology at the mome nt (both related and unrelated to simulations)\n\nVolker Springel: Home page on Max Plan ck Insitute site\n\nGADGET-4 code: wwwmpa.mpa-garching.mpg.de/gadget4/\n\nPaper: 2010.03567\n
\n\nIndex to Key Parts of the Talk:\n\n[00:00] Shaun's intro\n\n[00:45] Volker's opening comments about the paper and the code\n\n[01:26 ] Q&A: What two things would y ou want people to remember about this talk?\n\n[02:48] Diving into the details\n\n[03:51] Upcoming extremely large galaxy su rveys promise the next advances in cosmology: EUCLID\, LSST\, WFIRST\; their goals\; accurate theoretical predictions of comparable size as the surveys are needed\n\n[05:32] For GADGET to remain a useful code\, it needed profound upgrades\; what w e tried to achieve with GADGET-4\n\n[07:21] Historical evolution of GADGET code\n\n[08:52] Recent GADGET history\n\n[11: 36] Comments on the 2010.0356 7 paper\n\n[12:55] Simula tion output: Millennium-TNG example\n\n[14:33] The new GADGET-4 code scales beyond 10^5 cores\n \n[17:12] GADGET-4 shows muc h better strong and weak scaling as GADGET-2: Figure 61 in the paper\n \n[24:00] GADGET-4 can be us ed in a number of different configurations\n\n[25:01] The fast mulitpole method (FMM)\n\n[26:5 3] Novel MPI-3 based shared memory parallelization paradigm\n\n[28:08] Scaling of force errors: Fig 10\n\n[30:56] The optimum multipole order in terms of CPU consumption: Fig 13\n\n[32:43] Comparison with other codes\n\n[33:51] The tree force approximation: Fig 25/26\ , left panel\n\n[35:24] The FMM force field expansions: Fig 25/26\, right panel\n\n[37:25] Integer coordinates\n\n[40:42] Lightcones\, merger trees\, power-spectra\, etc: Fig 41\n\n[43:00] Subhalo tracking\; subhalo catalogues\; merger trees\n\ n[47:05] Summary\n\n[49: 00] Where to next?\n\n[5 2:37] Q&A: outside of your o wn research what do you think is the most interesting thing in cosmology a t the moment?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/27/ END:VEVENT BEGIN:VEVENT SUMMARY:Azadeh Maleknejad (CERN Department of Theoretical Physics) DTSTART:20210310T050000Z DTEND:20210310T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/28 DESCRIPTION:Title: A common origin for inflation\, neutrino mass\, baryogenesis\, and dark matter\nby Azadeh Maleknejad (CERN Department of Theoretical Phy sics) as part of Cosmology Talks\n\n\nAbstract\nAzadeh talks about a "beyo nd the standard model" of particle physics framework that appears able to simultaneously...\n\n- provide a particle physics backbone to inflation
\n- give neutrinos mass
\n- generate a dark matter candidate
\n- an d solve baryogenesis
\n\n...thus linking all of these cosmological prob lems. The framework can also deal with various particle physics problems\, such as the origin of the accidental B-L symmetry in the standard model\, the strong CP problem\, and the vacuum stability problem.\n\nSo\, it's sa fe to say that if the framework survives scrutiny it is a massive achievem ent.\n\nThe framework takes ideas from the "neutrino minimal standard mode l"\, specifically a new SU(2) gauge field that couples only to right hande d particles and can generate neutrino masses\, as well as provide a dark m atter candidate via the lightest right handed neutrino.\n\nIt then combine s those ideas with some from Azadeh's earlier work creating the model of g auge-flation. Specifically\, it allows for the fields that interact under this new SU(2) gauge symmetry to be actively generated during inflation. T his allows the vacuum fluctuations present during inflation\, and which ge nerate the curvature perturbation\, to also generate the particles that wi ll decay to dark matter and to generate the asymmetry in baryon number tha t eventually becomes the matter asymmetry.\n\nWhat's more\, the model make s a number of specific predictions. The primordial gravitational waves fro m inflation would have some non-Gaussianity and will be chiral. And\, the dark matter mass will be ~GeV - and would thus generate gamma rays in regi ons of very large dark matter density.\n\nIt will be fascinating to see ho w this framework develops\, and whether numerical reheating studies can sh ed light on the various particle production processes that generate the ma tter and dark matter during and after inflation...\n\nAzadeh: https://theory.cern/roster/male knejad-azadeh\n\nThe paper: SU(2)R and its Axion in Cosmology: A common Origin for Inflation\, Cold S terile Neutrinos\, and Baryogenesis [2012.11516]\n\n
\n\nIndex t o Key Parts of the Talk:\n\n[00:00] Shaun's intro\n\n[00:26] Azadeh's opening comments about the paper\n\n[01:10] Q&A: What two things would you want pe ople to remember about this talk?\n\n[01:59] Q&A: What was the motivation for this work? What has c hanged based on this research?\n\n[03:13] Getting into the details\n\n[03:51] Curious cosmological coincidences\n\n[04:3 0] Some conceptual issues in the SM of particle physics\n\n[06:17] The kinds of questions that Azadeh tried to answer in this pr oject\n\n[06:58] What do Gauge Fields do in Inflation?\n\n[07:43] Does it come with a cosmological signature?\n\n[08:49] How the Inflaton and its Gau ge Field are connected to the SM?\n\n[09:44] Is there a simple\, elementary\, & minimal set-up that can explain these cosmological and particle physics issues?\n\n[11:04 ] Primordial gravitational wa ves\n\n[12:30] Origin of matter asymmetry\n\n[13:36] Baryogenesis via Leptogenesis\n\n[16:56] Origin of neutrino mass and a dark matter particle nat ure possibility\n\n[19:54] Why Gauge Fields in Inflation?\n\n[20:43] SU(2)-Axion Model Building\; Gauge-flation and th e Chromo-natural model\; now ruled out by the data\; minimal scenario of S U(2)-axion inflation\n\n[24:45] Left-Right Symmetric Model\n\n[27:23] SU(2)R-Axion Inflation\n\n[31:02] SU(2)R Gauge Field Production by Axion\n\n [34:05] New Tensorial mode & Chiral GWs\n\n[35:04] N ovel Observable Signature: CMB\n\n[35:57] Parity Odd CMB Correlations: TB & EB != 0\n\n[38:11] Right-handed Lepton & Quark Production by SU(2)\n\n[39:48] Summary of the Mechanism\n\n[44:34] Compare the Minimal Set-up to SU(2)R-Axion Inflation\n\n[46:51] Q&A: Where to next?\n\n[51:20] Q&A: ou tside of your own research what do you think is the most interesting thing in cosmology at the moment?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/28/ END:VEVENT BEGIN:VEVENT SUMMARY:Scott Melville and Johannes Noller (Noller: ICG at Portsmouth\; Me lville: Cambridge) DTSTART:20210325T050000Z DTEND:20210325T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/29 DESCRIPTION:Title: Unitarity\, causality & locality: impacts on dark energy and gravi ty's speed\nby Scott Melville and Johannes Noller (Noller: ICG at Port smouth\; Melville: Cambridge) as part of Cosmology Talks\n\n\nAbstract\nJo hannes Noller and Scott Melville talk about their recent paper exploring t he impacts of certain positivity bounds on cosmological parameters.\n\nPos itivity bounds are restrictions on low energy effective parameters that ar ise from requiring the full high energy fundamental theory to satisfy cert ain criteria. It is possible to show that if\, e.g. all the interactions o f a full theory satisfies unitarity (conservation of information/probabili ty)\, causality and locality\, then a specific class of low energy theorie s must have the speed of light less than the speed of gravity.\n\nThe spec ific interactions Johannes\, Scott (and collaborator Claudia) used to show this are interactions between dark energy and standard model matter.\n\nT his condition actually ends up lying right in the region that observations prefer for this model\, effectively cutting the allowed parameter space i n half.\n\nPaper: https://arxiv .org/abs/2103.06855
\nJohannes Noller: https://www.icg.port.ac.uk/author/nollerj/
\nScott Melville: http://www.sco ttamelville.com
\nSupplemental Video: https://youtu.be/Z3Lx7VXB78E\n\n
\n\n[00:00] Shaun's intro\n\n[00:46] Noller: overview comments about the paper\n\n[04:24] Melville: two t akeaway messages to remember about this talk\n\n[05:47] Noller on the background motivation for thi s work\n\n[08:52] How thi s work relates to other papers in this area\n\n[09:05] A final comment on the motivation for this w ork\n\n[10:21] Q&A: Melvi lle comments on importing particle physics knowledge and understanding int o cosmology to constrain theories like dark energy\n\n[12:59] Q&A: Why had this not been done befor e? \n\n[13:59] Getting in to the details \n\n[16:41] The main idea behind the positivity bounds\n\n[16:57] A discussion on unitarity\, causality\, a nd locality\n\n[19:52] S ean's insert when editing: comments on the reason for the supplementary vi deo\n\n[20:54] Buildup t o the consequence in this specific model that speed of matter <= speed of gravity \n\n[24:15] Noll er: How these bounds impact current observational constraints\; a case stu dy\n\n[31:16] Data const raints with the positivity prior\n\n[34:54] Sean's explanatory comment insert during editing\n \n[36:22] Noller continuing the talk\n\n[37:34] Case study: 3 key observations\n\n[43:29] Melville reponds to a question by Shaun\n\n[46:07] Final comment by Noller\n\n[4 6:32] Q&A: Where to next?\n\n[47:44] Q&A: What do yo u foresee over the next 24 months?\n\n[53:04] Q&A: outside of your own research what do you think is the most interesting thing in cosmology at the moment?\n\n
\n\n< b>Supplemental Video:\n\n[00:00] Sean's comments on the reason for this supplementary video\n\n[ 00:46] Melville on the standa rd procedure for deriving positivity bounds\; a physical picture\n\n[0 4:17] Two important things\; and what causality buys you\n\n[05:15] Unitarity\n\n[06:07] Put both ingredients together\; why causality and unitari ty come together to give a positivity statement\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/29/ END:VEVENT BEGIN:VEVENT SUMMARY:Dan Thomas (Queen Mary University London) DTSTART:20210406T060000Z DTEND:20210406T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/30 DESCRIPTION:Title: The first model independent cosmological simulations of modified g ravity\nby Dan Thomas (Queen Mary University London) as part of Cosmol ogy Talks\n\n\nAbstract\nDan Thomas tells us about recent work first creat ing a framework for describing modified gravity in a model independent way on non-linear scales and then running N-body simulations in that framewor k.\n\nThe framework involves finding a correspondence between large scale linear theory where everything is under control and small scale non-linear post-Newtonian dynamics. After a lot of care and rigour it boils down to a modified Poisson equation - on both large and small scales (in a particu lar gauge).\n\nThe full generality of the modification to the Poisson equa tion allows\, essentially\, for a time and space dependent value for Newto n's constant. For most modified gravity models\, the first level of deviat ion from general relativity can be parameterised in this way (and we know that the deviations from general relativity are small because so far we ha ven't found any!!)\n\nThe cosmological simulations are then done by having Newton's constant just vary over time (i.e. it is constant in space). Thi s allows them to actually do some simulations\, but in future work they wi ll go beyond this particular simplification.\n\nThey then compare the simu lation results to semi-analytic models like Halofit and ReACT. Halofit is explicitly just applicable to ΛCDM model but does surprisingly well. ReAC T however still does much better at fitting e.g. the matter power spectrum and model Euclid lensing observables.\n\nFuture work will examine more cl osely why ReACT fits so well and aim to improve the fit even better so tha t e.g. Euclid and/or the Vera C. Rubin Observatory (LSST) will be able to use this method to constrain modified gravity without needing to run a new simulation for every step of a Monte Carlo parameter fit.\n\nTheory frame work paper: https://arxiv.org/a bs/2004.13051\n\nSimulation paper: https://arxiv.org/abs/2103.05051\n\nDan: https://danbthomas1.wixsite.com/research \n\n
\n\n[00:00] Shaun's in tro\n\n[00:40] Dan's summa ry comments about the paper\n\n[01:15] Q&A: What are two takeaway messages to remember about this ta lk?\n\n[01:54] Q&A: What is the specific motivation for this work? What was unsolved? Why didn't it happen earlier?\n\n[03:20] Recap summarizing 15 years work: Model independent modified gravity in cosmology\n\n[05:30] What 's the problem? The elephant in the room\n\n[06:06] Poisson: a clue to the path forward?\n\n[08 :06] Getting into the details of the papers (theory and simulation)\n\n[08:22] A tale of two limits\, and the non-linear scale\n\n[11:43] A quick aside\n\n[12:12] GR+LCDM: 2 ingr edients: Comment that has relevance on next slide: "there is no interm ediate regime in a LCDM cosmology"\n\n[13:01] Post-Friedmann: "master" equations\n\n[17:19] GR + LCDM\n\n[19:50] Back to modified gravity\n\n[21:40 ] Building towards something that's useful for data analysis: 7 simulations\; Table 1 and Figure 2 in 2103.05051\n\n[27:23] z= 0 phenomenology: Figure 7 upper left panel in 2103.05051 \n\n[29:28] < a href="https://youtu.be/orMFALXtU8g?t=1768">Lensing observables: Figu re 9 in 2103.05051\n\n[33:21] Fitting functions: Figure 3\n\n[36:58] Fitting functions and Lensing: Figure 10\n\n[40:59] < a href="https://youtu.be/orMFALXtU8g?t=2459">Where to next?\n\n[44:00] Q&A: outside of your own re search\, what do you think is the most interesting thing in cosmology at t he moment?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/30/ END:VEVENT BEGIN:VEVENT SUMMARY:Steffen Hagstotz (Stockholm University) DTSTART:20210422T060000Z DTEND:20210422T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/31 DESCRIPTION:Title: The Hubble parameter measured with Fast Radio Bursts\nby Steff en Hagstotz (Stockholm University) as part of Cosmology Talks\n\n\nAbstrac t\nSteffen tells us about how the dispersion measure of fast radio bursts (FRBs)can be used to measure the distance to FRBs. Therefore\, if we can f ind the host galaxies of FRBs and measure their redshifts we can measure t he expansion rate (Hubble parameter) with FRBs.\n\nAnd\, he and his collab orators have done just that. At the moment the uncertainty is relatively l arge\, but they still get a result within 10% of the more precise measurem ents (and consistent with both CMB and supernovae)\, indicating that they' re doing the right thing.\n\nIn the near future (less than five years) we' ll have (hopefully) more than 500 FRBs and a ~% level accuracy measurement of H0. These are exciting times for FRBs!\n\nPaper: https://arxiv.org/abs/2104.04538\n\nSteffen: https://www.su .se/english/profiles/...\n\n
\n\nIndex to Key Parts of the Talk\n\n[00:00] Shaun 's intro\n\n[01:16] Q&A: W hat two things would you want people to remember about this talk?\n\n[ 02:06] Q&A: What was the moti vation for this work? What was unsolved? Why wasn't this done earlier? \n\n[03:47] Getting into the details\n\n[07:40] Overvi ew of Proposed Mechanisms\n\n[09:05] Known FRBs\n\n[10:04] Dispersion measure: basically\, the integrated electron densi ty along the LoS\n\n[12:52] 3 contributions to the dispersion measure: Milky Way\, LSS\, host galax y\; modeling for each component\n\n[16:21] The LSS component\n\n[18:14] FRB statistics\n\n[22:16] FRB distance scale: baryon density issues\n\n[26: 44] Figure 2 from the 2104.0 4538 paper: Dispersion measure - redshift relation\n\n[29:47] Figure 1: Hubble constant constraint s\n\n[33:03] The Future: When can FRBs be competitive to measure H0 at the percent level?\n\n[ 34:02] Figure 3: Expecte d joint constraints on H0\, the matter density\, and the mean host dispers ion measure contribution from a mock sample of 500 FRBs\n\n[36:04] Forecast\n\n[36:36] When do we expect to get to 500 events? \n\n[39:48] What can be done with larger samples\n\n[40:26] Summary\n\n[43:54] What's coming next?\n\n[45:39] A new final question: What current cosmology work do you thi nk is particularly under-appreciated by the community?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/31/ END:VEVENT BEGIN:VEVENT SUMMARY:Peter Coles (Maynooth University) DTSTART:20210502T060000Z DTEND:20210502T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/32 DESCRIPTION:Title: The Open Journal of Astrophysics (and why you should be publishing in it)\nby Peter Coles (Maynooth University) as part of Cosmology Tal ks\n\n\nAbstract\nPeter shares his thoughts on the nature of scientific pu blishing and why it is so profitable for the big publishing companies. Pet er isn't a fan of the current state and has taken practical steps to impro ve it.\n\nThe biggest practical step he's taken is to create The Open Jour nal of Astrophysics. This journal is entirely not for profit runs off a $1 000 a year budget and (unlike for-profit journals) charges nothing to anyo ne in the scientific publishing process (authors\, libraries\, etc). And a ll the papers it publishes are 100% open access on the arXiv.\n\nThe jour nal is a fully functioning journal. If you submit a paper there it will ge t peer-reviewed\, if it is accepted it will get cross-referenced at all th e relevant places\, will receive a doi and will have its citations counted at Inspire\, ADS\, etc.\n\nThe journal needs to be running for three year s to get an impact factor\, which won't happen until 2022\, but it will be approximately 10-ish (by my extrapolation of his minimum estimate - see v ideo for details) which is very high by astrophysics journal standards (if you care about that sort of thing).\n\nAnd... they've already published p apers by big consortia like LSST and eROSITA.\n\nIt's a baby step in overt hrowing the early 20th century system we're still using in 2021\, but it i s at least a step. We should embrace it.\n\nPeter: https://www.maynoothuniversity.ie/ people/peter-coles
\nHis blog: https://telescoper.wordpress.com/
\nThe Journal: https://astro.theoj.org/\n\n
\n\n[00:00] < a href="https://youtu.be/EjKp-XX7S80?t=0s">Shaun's intro\n\n[01:43] Peter's opening comments about the Open Journal of Astrophysics (OJAp) \n\n[02:07] Q&A: What two things would you want people to r emember about this talk?\n\n[03:25] Peter's thanks to Maynooth U for it's support of OJAp\n\n[0 4:02] The Academic Publishing Industry (an exposé!)\n\n[10:10] Why Open Access?\n\n[17:40] Open Access: Green\, Gold\, & Diamond: 3 categories of o pen access\n\n[20:34] Peter' s comments about the arXiv\n\n[24:51] Why Academic Journals?: the OJAp as an arXiv overlay jou rnal to referee the arXiv submissions\, issue a DOI\, register metadata an d citations thru the crossref system\n\n[27:16] The Open Journal of Astrophysics: also note sister journal - the Journal of Open Source Software\n\n[31:02] The author keeps the copyright: with mos t journals\, the author signs the copyright to the journal\n\n[32:37] The arXiv id is the DOI identifi er for all OJAp papers\n\n[32:57] The paper submission process\n\n[34:45] The Journal blog\n\n[35:50] The 6 arXiv astro-ph categories in relation to the OJAp \n\n[37:30] What the OJAp does\n\n[39:06] What the OJAp does differently\n\n[44:00] In two networks: DOAJ and Free Journal Network \n\n[44:42] Some Statistics< /a>: includes comments on the acceptance rate\, reviewers\, review process \, and issues re fees\n\n[55:23] The future?: much discussion on Journal Impact Factor\n\n[01:04:1 5] How to support the OJAp: e.g.\, consider submitting papers\, refereeing\, and supporting use of the arXiv\; OJAp does not need financial contributions but arXiv does\n\n [01:10:26] Q&A: What current cosmology work do you think is particularly under-appreciated by the comm unity?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/32/ END:VEVENT BEGIN:VEVENT SUMMARY:Eloisa Bentivegna (IBM) DTSTART:20210525T060000Z DTEND:20210525T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/33 DESCRIPTION:Title: Evolution of a periodic eight-black-hole lattice in numerical rela tivity\nby Eloisa Bentivegna (IBM) as part of Cosmology Talks\n\n\nAbs tract\nEloisa tells us about her work from 2012 (and following years) cons tructing a model universe space-time out of lattices of blackholes. \n\nTh e motivation for this is to take a very bottom up approach to cosmology. W e know that around isolated objects the correct metric is close to the Sch warzschild metric\, so in principle the full metric of the universe should be able to be written as a patching together of such metrics. On the othe r hand\, the universe on large scales is statistically homogeneous and iso tropic and the Friedmann-Robertson-Walker metric appears to fit the data w ell. \n\nWhat Eloisa and colleagues wanted to know is how these two paradi gms come together\, and they more or less found the answer.\n\nEloisa is a lso employed not at a university\, or any other institute we might normall y expect to find a cosmologist. She is employed at IBM. However\, she hasn 't stopped doing cosmology research\, IBM pay her to do numerical relativi ty and cosmology. In the video she talks a lot about how this is possible and what IBM want from her as an employee and why this isn't so unique. In fact\, she's not even IBM's first numerical relativist!\n\nEloisa: https://researcher.watson.ibm.com/researcher/view.php?person= ibm-Eloisa.Bentivegna
\n1st paper: [1204.3568] Evolution of a periodic eight-black-hole lattice in numerical relativity
\n2018 review article on the topic: [1801.01083] Black-Hole Lattices as Cosmo logical Models
\n\n
\n\n[00:00] Shaun's intro\n\n[02:33] Eloisa's historical overview and motivation for this work\n \n[04:54] Black hole lattices \n\n[09:54] Initial choic e between two options: (1) keep a zero extrinsic curvature\, but choos e a conformal metric that's not flat\, vs (2) keep a flat conformal metric but use a non-zero extrinsic curvature\n\n[12:21] Completely analytic initial conditions - huge simpli fication\n\n[14:45] Speci al solution - multiple black holes can be obtained by superimposing the fu ndamental solution\n\n[16:20] Six possible configurations\n\n[17:01] Invert the stereographic projection\n\n[17:54] Eloisa's email update subsequen t to talk\n\n[19:51] The 8-black hole universe and its full-GR evolution\n\n[21:02] Tools used: Einstein Toolkit and Cosmo Toolkit\n\n[21:29] Evolu tion equations away from the hypersurfaces\n\n[24:14] Plots of some of the observables measured du ring the evolution\n\n[26:26] Status slide\; main conclusions\n\n[28:28] Where to from here?\n\n[32:09] Q&A: Can inhomogeneous but purely GR effec ts model the H0 tension?\n\n[35:56] Eloisa's role as a computational physicist at IBM\n\n[39:1 4] Comments on her job descr iption\n\n[42:05] Why wo uld a business be interested in basic science? And in cosmology and numeri cal relativity?\n\n[45:42] A historical trivia example of an early numerical relativity paper\; fi rst author is an IBMer\n\n[46:58] Q&A: What do you think is an especially underappreciated aspect of cosmology research being done currently?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/33/ END:VEVENT BEGIN:VEVENT SUMMARY:Asta Heinesen and Hayley Macpherson (Canterbury U.\, Cambridge) DTSTART:20210603T060000Z DTEND:20210603T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/34 DESCRIPTION:Title: How much are local anisotropies biasing our measurements (e.g. H0) ?\nby Asta Heinesen and Hayley Macpherson (Canterbury U.\, Cambridge) as part of Cosmology Talks\n\n\nAbstract\nAsta Heinesen and Hayley Macpher son tell us about their recent papers developing a formalism for measuring local parameters without assuming local isotropy (and homogeneity) and pr edicting what we should expect for the parameters in this formalism when w e go beyond the isotropic approximation of FRW.\n\nAsta talks about her pa per from last year which developed the formalism\, and how a finite number of terms can capture all the expected behaviour in the anisotropic lumino sity distance\, at each order of redshift.\n\nHayley then talks about how\ , together\, they applied Asta's formalism to Hayley's fully relativistic simulations of cosmology.\n\nThey show the results for the generalised Hub ble\, "deceleration" and jerk parameters. It turns out that when you remov e the assumption of isotropy these parameters do indeed depend\, sometimes very significantly\, on which direction you look on the sky.\n\nHow much this is impacting our measurements depends\, among other things\, on how f ull your sky coverage is.\n\nAsta: https://inspirehep.net/authors/1726735
\nHayley: https://hayleyjm.github.io/\n\nAsta's pa per: https://arxiv.org/abs/2010 .06534
\nAsta and Hayley's paper: https://arxiv.org/abs/2103.11918\n\nThe paper Hayley mention s where she went as non-linear as possible with full general relativity: < a href="https://arxiv.org/abs/1807.01711">https://arxiv.org/abs/1807.01711 \n\n
\n\n[00:00] Shaun' s intro\n\n[01:39] Hayley - quick summary of this work\n\n[02:24] Q&A: What two things would you want people to remember abou t this talk?\n\n[03:33] A sta - background and motivation for this work\n\n[08:12] Review of FLRW models\; "FLRW cosmography" \n\n[10:53] The general g eometric case\n\n[12:05] General luminosity distance "Hubble law"\n\n[15:22] Observer congruence\n\n[17:59] Hayley clarifies these are naturally tru ncated multipole series\n\n[18:34] Finite set of degrees of freedom\n\n[20:59] The deceleration parameter\n\n[22:36] < a href="https://youtu.be/cbmMhICi-6c?t=1356">Q&A about luminosity distance in this work\n\n[25:39] Hayley - background on the simulations: mimicking as closely as possi ble the generality of the formalism\, using numerical relativity\n\n[27:44 ] Numerical relativty codes< /a>\n\n[28:14] Numerical rel ativity for inhomogeneous and anisotropic cosmology\n\n[30:26] A note about smoothing\n\n[33:0 6] Discussion on gevolution< /a>\n\n[35:14] Comments on F igure 1 from the 2103.11918 paper\n\n[37:07] What the cosmological parameters would look like for individual observers in the simulations\n\n[39:13] Comments on Figure 3 from the 2103.11918 paper< /a>\n\n[43:16] Figures 2 and 4\n\n[45:08] Anisotropi c contributions: "maximal sky deviation"\n\n[46:29] Exaggerated case of an "unfairly sampled sky"< /a>: Figures 2b and 5\n\n[49:49] Main take-aways\n\n[53:19] Wrap-up: additional points not previously mentioned\n\n[56:39] Q&A: What do you think is a n especially underappreciated aspect of cosmology research being done curr ently?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/34/ END:VEVENT BEGIN:VEVENT SUMMARY:H. Gil Marín\, M. Simonovic\, T. Tröster (U Barcelona\, CERN\, U Edinburgh) DTSTART:20210623T060000Z DTEND:20210623T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/35 DESCRIPTION:Title: What is the best way to analyse galaxy clustering data? Panel even t\nby H. Gil Marín\, M. Simonovic\, T. Tröster (U Barcelona\, CERN\, U Edinburgh) as part of Cosmology Talks\n\n\nAbstract\nThis is a recordin g of a panel event run by the organisers of the Cosmology from Home confer ence series: https://cosmologyfromhome.com/\n\nThe topic was a compariso n of the relative merits of "full shape" and "template" methods to analyse galaxy clustering data. Essentially the difference comes down to whether you consider the entire power spectrum as a whole and fit to it in all its glory\, or break into separate pieces that encapsulate specific physics e ffects.\n\nEach method has its own merits and issues.\n\nRecorded video on YouTube\n\nThe thre e panelists were:\n\nHéctor Gil Marín: https://www.ub.edu/bispectrum\n\ nMarko Simonovic: https://theory.cern/roster/simonovic-marko \n\nTilman Tröster: https://tilman.troester.space\n\nThe papers that cam e up in discussion were:\n\nShapeFit: Extracting the power spectrum shape information in galaxy surveys beyond BAO and RSD: https://arxiv.org/abs/21 06.07641\n\nThe Completed SDSS-IV Extended Baryon Oscillation Spectros copic Survey: N-body Mock Challenge for the Quasar Sample: https://arxiv.o rg/abs/2007.09003\n\nThe Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: measurement of the BAO and growth rate of structure of the luminous red galaxy sample from the anisotropic power spectrum bet ween redshifts 0.6 and 1.0: https://arxiv.org/abs/2007.08994\n\n
\n \n[00:00] Shaun's intro: this is a new format partially as an experiment for Cosmology from Home bu t also as an interesting event in it's own right\; the aim is a collaborat ive pursuit of understanding\, not a debate\n\n[01:32] Intro to the panelists' discussion issue: ful l-shape vs template methods\; Shaun's video is a little blurry at first\, audio is clear\, panelists' video is clear\n\n[04:09] Héctor Gil Marín introduces himself\n\n[04: 53] Marko Simonovic introduce s himself\n\n[05:14] Tilm an Tröster introduces himself\n\n[05:33] Shaun: three separate directions to the discussion\n\ n[06:26] Héctor: what do we want from a cosmological analysis?\n\n[08:49] Marko: defending the concept of assuming a model and doing parameter fits to the model\; not a problem\, a strength of the full shape analysis approach\n\n[10:52] Responses by Héctor and Tilman\n\n[13:03] Marko - what to do when have systematics or b ad chi-squared analysis\n\n[14:41] Héctor: fσ8 overview\; what compressing the variables allows< /a>\n\n[18:34] Marko - the b enefits of full shape analysis\n\n[20:22] Tilman's agreement and further comments\n\n[20:58] < a href="https://youtu.be/9yVcD9cvzPo&t=1258">What info are we gaining by g etting extra precision on model parameters? Marko response and Héctor rep ly\n\n[25:27] Héctor on the claim that templates are more model independent\; Marko reply and fur ther discussion based on Figures 2 & 3 from 2106.07641\n\n[37:56] Seeking input for a summary stat ement at this point of discussion\n\n[42:36] Héctor on what fσ8 means and what template correcti ons may be needed\; discussion\n\n[49:35] Tilman's input on the issues\; further discussion\n\ n[52:08] Last question: when data isn't independent\, how do you combine the data? \n\n[01:00:08] If someone in the audience w ants to work on this\, what is something they could dive into? Also\, what about a template method for the CMB?\n\n[01:03:55] Comments by attendee and co-author Licia Verde (2106.07641)\n\n[01:07:54] Marko believes next generation surveys will transition to full shape a nalysis\n\n[01:08:43] In what ways you've gained important insights or changed your mind between t he pre-discussion and this panel event?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/35/ END:VEVENT BEGIN:VEVENT SUMMARY:Harry Goodhew and Gordon Lee (University of Cambridge) DTSTART:20210802T060000Z DTEND:20210802T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/36 DESCRIPTION:Title: Unitarity constraints on cosmological correlators (valid in *any* flat FLRW metric)\nby Harry Goodhew and Gordon Lee (University of Camb ridge) as part of Cosmology Talks\n\n\nAbstract\nHarry Goodhew and Gordon Lee talk about their recent work on “cosmological correlators”.\n\nObs ervationally these would be power spectra\, bispectra\, etc\; however on t he theory side they find it easier to work with pieces of the “wavefunct ion of the universe”\, which are closely related to observational correl ation functions.\n\nThey show constraints on the form these correlators ca n take that arise from imposing unitarity during inflation. Contrary to pr ior expectations these constraints apply not just in space-times that are exactly de Sitter\, but in fact in any flat FLRW space-time.\n\nThe most r elevant paper: https://arxiv.or g/abs/2104.06587\n\nHarry: https://www.maths.cam.ac.uk/person/hfg23
\nGordon: https://www.damtp.cam.ac.uk/per son/mhgl2\n\n
\n\n[00:00] Shaun's intro and overview\n\n[01:23] Harry describes the work done in this paper: (Harry's part of the talk)\n\n[02:01] Q&A: What two things do you want people to remember about this talk?\ n\n[02:34] Q&A: The motivatio n for this paper\, and why was this work done now and not earlier? \n\ n[03:48 The wave function of the universe\n\n[08:07] M odel Based Calculations\n\n[10:51] Bootstrapping: try to directly calculate what the observable s are from fundamental principles\; benefits over the model-based approach \n\n[12:38] The ultimate goal of the cosmological bootstrap program\n\n[12:53] The most important fundamental principles in the Cosmological Bootstrap\n\n[15:22 Q&A: what about multi-field models?\n\n[16:34] What is unitarity? (Gordon's part of the tal k)\n\n[17:52] How to see unitarity?\n\n[19:01] H ermitian analyticity\n\n[21:27] Discontinuity: (culminating in Figure 1 of paper)\n\n[26:29] < a href="https://youtu.be/Iz9AIE0zJNU?t=1589">How do we find out if a field is Hermitian analytic?: main result of paper\n\n[28:49] Q&A: What is the implication of these res ults?\n\n[29:08] Manifes t Locality\n\n[32:12] Co mbining unitarity and locality\n\n[33:13] What next?\n\n[37:51] Q&A on observations that would be a consequence of this wo rk\n\n[42:14] Q&A: What is an especially underappreciated aspect of cosmology research being done currently?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/36/ END:VEVENT BEGIN:VEVENT SUMMARY:Lloyd E. Knox\, Frances-Yan Cyr-Racine (U of New Mexico\, UC Davis ) DTSTART:20210909T060000Z DTEND:20210909T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/37 DESCRIPTION:Title: A subtle cosmological symmetry & mirror dark sector might fix H0\nby Lloyd E. Knox\, Frances-Yan Cyr-Racine (U of New Mexico\, UC Davis) as part of Cosmology Talks\n\n\nAbstract\nFrancis-Yan Cyr-Racine and Lloy d Knox talk about their work with Fei Ge pointing out a symmetry present i n most cosmological observables. \n\nThe symmetry involves rescaling (almo st) *all* the densities and temperatures in the universe thus leaving any dimensionless observables unchanged. When exploited it might pave a way to solving the Hubble tension as it allows one to change H0 without changing predictions for other crucial cosmological measurements (most of which ar e e.g. temperature\, density\, etc *contrasts* not absolute measurements). \n\nThe first major road-block is that the CMB temperature is an absolute measurement and a very precise one and thus one can't just casually chang e it in one's model\n\nOne way to implement this is therefore to introduce a mirror dark sector. This allows the measured photons to be unchanged\, but the overall density of radiation to be rescaled. The mirror world must be very similar to our world so that the exact rescaling happens (i.e. th ere must be mirror electrons\, mirror protons\, mirror neutrinos\, etc too ).\n\nThere's is one remaining (potentially fatal) flaw\, which is that on e must also rescale the photon mean free path near to CMB formation as it affect observables and doesn't change just be adding a dark sector. One wa y to approach a solution there would be to modify the primordial helium ab undance\, as this would change the density of free electrons at the time o f CMB formation. However\, this runs into trouble with observations and wo uld need a model of nucleosynthesis that allows for this change...\n\n... so this isn't a complete solution at this point\, but definitely something to keep an eye on. \n\nMaybe the dark sector affects the helium abundance \, maybe it changes the free electron density\, maybe something else can e xploit this symmetry and not run into this problem!?\n\nThe model has just *one* free parameter though and\, at least phenomenologically\, is able t o completely solve the Hubble tension - albeit with the creation of a prim ordial helium tension!\n\nCuriously\, the best fit temperature of the dark photons is very close to the temperature of the cosmic neutrino backgroun d\, suggesting that *maybe* the production of the mirror world is related to neutrino physics somehow.(!?)\n\nLloyd: https://www.lloydknox.com/
\nFrancis-Yan: https://darkuniverse.unm.edu/
\nThe paper: https://arxiv.org/abs/2107.13000
\n\n
\n[00:00] Shaun's intro\n\n[00:50] Summary overview by Lloyd\n\n[02:17] Q&A: What two things do you want people to remember about this talk?\n\n[03:56] What were the m otivations for this work?\n\n[05:47] Frances-Yan on the motivations and how this work developed \n\n[07:56] Getting into the details\n\n[08:26] The Hu bble constant\, measuring angles and redshifts\, insensitivity of redshift s/angles to actual distances\n\n[09:34] Invariance of angles under uniform rescaling of the Hubble rate\n\n[10:26] But what if all length scales are uniformly rescaled?\n\n[11:38] Basic geometry and dimensional analysis \n\n[12:25] Special feature o f our universe: initial conditions\n\n[14:40] The scaling "recipe"\n\n[16:14] An exact (if unphysical) scaling symmetry\ n\n[17:40] This recipe works - it really leaves the CMB temperature/polarization invariant\n\n[18: 49] Reality check: Symmetry breaking\n\n[21:05] Disc ussion on recombination not being an equilibrium process\n\n[22:40] Exploiting the symmetry: Mirro r World - plus comments on the many mirror sector studies done for oth er reasons than cosmology\n\n[27:07] Adjusting the photon scattering rate\n\n[29:08] Zeroth Test: The exact symmetry\n\n[3 1:29] First (real!) test: Re combination\n\n[32:14] S econd test: Compatibility with the cepheid-calibrated distance ladder (Fig. 1 top left panel from the paper)\n\n[34:55] Mirror Sector Freedom (Fig. 2)\n\n[40:37] Open Questions\; What Comes Next?< /a> (comments by both Lloyd and Frances-Yan)\n\n[46:10] Q&A: What work being done in cosmology at the moment do you think is particularly underappreciated? (Frances-Yan)\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/37/ END:VEVENT BEGIN:VEVENT SUMMARY:Helen Shao\, Francisco Villaescusa-Navarro (Princeton University) DTSTART:20210927T050000Z DTEND:20210927T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/38 DESCRIPTION:Title: Machine learning unveiling cosmology | subhalo masses and the viri al theorem\nby Helen Shao\, Francisco Villaescusa-Navarro (Princeton U niversity) as part of Cosmology Talks\n\n\nAbstract\nHelen and Francisco ( Paco) tell us about their recent work using neural networks to predict the masses of subhalos within simulations. They find that the neural network trained on a subset of the subhalos is very good at predicting subhalo mas ses for the rest of the data.\n\nRestricting themselves to just three para meters\, the radius\, the velocity dispersion and "Vmax" (the maximum circ ular velocity of the subhalo) the neural network does almost as well. With this as motivation they look for analytic models that might capture what the neural network is seeing. they find a simple three parameter power-law does OK using just radius and velocity dispersion as inputs - but a runni ng power-law with all three (radius\, velocity dispersion and Vmax) does e xtremely well (almost as well as the neural network).\n\nInterestingly\, a lthough the neural network starts to perform poorly when extrapolated to m asses beyond its training set\, the analytical model manages to still perf orm well. This suggests that they might be on to some genuine new physical insight about how these parameters combine to determine a subhalo mass.\n \nVarious subtleties suggest that this new insight might be related to the virial theorem\, but more exploration would be needed to be absolutely su re how.\n\nThe work here is part of the CAMELS project\, which has thousan ds of N-body and hydrodynamic simulations of the universe from which to tr ain neural networks on.\n\nHelen: https://www.linkedin.com/in/helen-shao-794641169
\nPaco: https://franci scovillaescusa.github.io/
\nCAMELS: https://www.camel-simulations.org/
\n\nThe paper: https://arxiv.org/abs/2109.04484
\n\n
\n[00:00] Shaun' s intro\n\n[00:59] Summary overview by Helen\n\n[01:21] What two things do you want people to remember about this talk? (Paco) \n\n[02:06] What was the motivation for this work? (Helen)\n\n[03:53] What are the parameters of interest in this work? \n\n[05:30] What some of the parameters mean (Paco)\n\n[07:15] General Methodology (Helen)\n\n[08:23] Symbolic Regression\n\n[09:02] Are the parent halo properties relevant in th is work? (Paco)\n\n[09:33] Continuing with Methodology (Helen)\n\n[13:13] CAMELS-IllustrisTNG (and TNG100/TNG300) vs CAMELS- SIMBA\n\n[15:55] Other Te sts: higher z\, central subhalos vs satellites\, N-body simulations\, etc\n\n[17:56] The neural ne twork found a universal relation\n\n[20:37] Testing the analytic equations vs the four simulations \n\n[23:00] Conclusions< /a>\n\n[24:15] Physical Inte rpretation\n\n[26:10] Qu estions period\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/38/ END:VEVENT BEGIN:VEVENT SUMMARY:James Alvey (U. Amsterdam\, GRAPPA) DTSTART:20211014T050000Z DTEND:20211014T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/39 DESCRIPTION:Title: Big Bang Nucleosynthesis in 2021\nby James Alvey (U. Amsterdam \, GRAPPA) as part of Cosmology Talks\n\n\nAbstract\nJames Alvey tells us about the general state of BBN in 2021.\n\nHe gives a really nice pedagogi cal overview of the physics that goes into BBN calculations relevant for 2 021 observations\, talking through each of the relevant epochs (neutrino d ecoupling\, the deuterium bottleneck\, etc).\n\nHe gives particular emphas is to the recent LUNA measurements of the D + p →γ + 3He reaction (or d euterium + proton goes to photon and 3-Helium). This was previously the so urce of greatest uncertainty in predicting the final deuterium abundance o f BBN.\n\nFinally\, he talks about the implications of the LUNA measuremen ts on possible new physics beyond the standard model\, in particular possi ble thermal relics.\n\nThe Talk: ht tps://youtu.be/Hv8sbRwbSU8
\nThe LUNA paper: https://www.nature.com/articles/s415 86-020-2878-4 (no arXiv version\, I think?)
\nJames' original paper on thermal relics: https://arx iv.org/abs/1910.01649
\nAddendum to James' paper analysing implicat ions of LUNA: https://arxiv.org /abs/2107.11232
\n\n
\n\nIndex to Key Parts of the Talk:< br>\n
\n[00:00] Shaun's int ro\n\n[00:25] Summary over view by James: a theme: why BBN in 2021 is different than BBN in 2019\ n\n[01:52] What two things do you want people to remember about this talk?\n\n[03:07] More detail on why this is important for u s in 2021\n\n[04:59] Comm ents on the baryon-photon ratio (used interchangeably with the baryon dens ity)\n\n[05:50] Getting i nto the details: What Can You Measure with BBN in 2021?\n\n[06:23] Why an addendum rather than a wh ole new paper?\n\n[07:12] Why Now? Current Status of BBN\n\n[09:29] Q&A on the primordial lithium abundance\n\n[10:27] < a href="https://youtu.be/Hv8sbRwbSU8?t=627">Discussion on nuclear reaction rate measurements\n\n[13:09] What Quantities Does BBN "See"?\n\n[14:00] The Physics of BBN\n\n[20:40] Solving the Cosmology\n\n[23:19] Temperature-to-Time Relation\n\n [24:39] Neutrino decoupling< /a>\n\n[25:40] Electron-posi tron annihilation\n\n[25:50] The BBN Reaction Network\n\n[29:43] Protons and Neutrons: weak freeze-out\n\n[31:06] Neutron Decays\n\n[32:52] The Bottleneck\n\n[36:38] Producing Helium-4\n\n[4 4:46] Describing the Network \n\n[46:42] LUNA and Deu terium\n\n[54:25] Impact on Constraints\n\n[58:02] Summary and Conclusions\n\n[01:01:56] Q&A: What is an especially underappreciated aspect of cos mology research being done currently?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/39/ END:VEVENT BEGIN:VEVENT SUMMARY:Song Huang and Alexie Leauthaud (Princeton and UCSC) DTSTART:20211029T050000Z DTEND:20211029T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/40 DESCRIPTION:Title: Stellar mass in a *single* galaxy's outskirts reveals the *whole* cluster mass\nby Song Huang and Alexie Leauthaud (Princeton and UCSC) as part of Cosmology Talks\n\n\nAbstract\nSong Huang and Alexie Leauthaud tell us about their new galaxy cluster finder\, which uses the stellar mas s in the outer region of a galaxy as a method to determine the mass of the galaxy's cluster.\n\nIt feels a bit like magic (to me) that the stars in individual galaxies can be used to weigh the mass of the whole cluster\, b ut like other mass proxies one can devise a scaling relationship between t he proxy and the mass - and then the proof is in the empirical pudding.\n\ nConcerning that pudding\, Song and Alexie's new proxy has a comparably sm all scatter in its scaling relation i.e. when compared to the most common proxy for optical surveys\, the richness (i.e. the number of galaxies of a certain type in the cluster).\n\nThe most massive clusters found by this method are also more easily modelled than the most massive clusters found via richness. i.e. there seem to be smaller systematic effects that need t o be taken account.\n\nSo\, whatever magic is going on\, it's working!\n\n Overall\, Song and Alexie think a holistic approach to weighing galaxy clu sters is the best way to go\, using richness and stellar mass estimates\, as well as observables from surveys at other wavelengths like X-Ray temper ature and the SZ effect on CMB photons that are scattered by hot gas insid e clusters.\n\nIt looks like an exciting\, multiwavelength\, future for ga laxy cluster cosmology\, which should further open up a very non-linear di stance scale to precision tests of the growth of structure\, modified grav ity and the primordial density perturbations.\n\nSong: https://dr-guangtou.github.io/
\nAlexie: https://alexie.sites.ucsc.edu/
\nThe paper: https://arxiv.org /abs/2109.02646
\n
\n\n[00:00] Shaun's intro to the work\n\n[00:45] Song's summary\n\n[04:50] Two simple thing to remember about the talk\n\n[ 06:16] What makes this work re levant in 2021?\n\n[12:18] The details...\n\n[40:33] What comes next?\n\n[46:17] What is particularly underappreciated in cosmology at the moment?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/40/ END:VEVENT BEGIN:VEVENT SUMMARY:Hironao Miyatake (Nagoya University\, NASA/Caltech Jet Propulsion Lab) DTSTART:20211104T050000Z DTEND:20211104T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/41 DESCRIPTION:Title: Hyper Suprime Cam's (HSC) latest constraints on Ωm and σ8!\n by Hironao Miyatake (Nagoya University\, NASA/Caltech Jet Propulsion Lab) as part of Cosmology Talks\n\n\nAbstract\nHironao tells about how the Hype r Suprime Cam survey collaboration have taken their own data\, and the BOS S data from SDSS to do a joint cosmology constraint.\n\nSpecifically\, the y take the autocorrelation function of the BOSS galaxies and the cross-cor relation of HSC weak lensing data with the BOSS galaxies to break degenera cies between cosmology and galaxy bias\, thus allowing the full informatio n in the galaxy data to be usable (or at least\, lots more of it).\n\nThey work hard to extract information from the small scales in these two probe s\, using a cosmology emulator and halo occupation model\, and they includ e various consistency tests to show that their analysis is robust. (They a lso did the analysis blind\, to avoid human bias as much as possible).\n\n The final constraints are comparable to recent similar DES and KiDS constr aints\, and consistent with both\, but this analysis have a somewhat diffe rent degeneracy in the Ωm and σ8 plane.\n\nPersonally\, I'd now love to see some sort of combined analysis of all three weak lensing probes as the y're all consistent with each other and I expect the combined constraints would be in a lot of tension with Planck (especially because of this diffe rent degeneracy direction).\n\nHironao: https://sites.google.com/view/hironaomiyatake/h ome\n\nPaper: https://arxiv .org/abs/2111.02419\n
\n\n[00:00] Shaun's introduction\n\n[01:47] Two things to remember from the talk\n\n[03:05] What is the background?\n\n[ 05:30] Galaxy-galaxy lensing x galaxy-galaxy clustering\n\n[11:59] Subaru Hyper Suprime-Cam (HSC)\n\n[14:32] HSC SSP Survey\n\n[17:10] G-g lensing and clustering measurements by HSC-Y1 and BOSS\n\n[22:33] Emulator-based halo model\n\n[23:55] Dark Emulator modeling\n\n[26:43] Modeling galaxy-halo connection\n\n[32:18] Cosmological inference: syst ematic tests\n\n[35:38] Cosmological inference: results\n\n[40:52] What is coming next?\n\n[42:42] What is underappreciated by the cosmology commu nity?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/41/ END:VEVENT BEGIN:VEVENT SUMMARY:Tilman Tröster (University of Edinburgh) DTSTART:20211115T050000Z DTEND:20211115T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/42 DESCRIPTION:Title: Baryon feedback measured via tSZ (cosmological error bars 50% smal ler)\nby Tilman Tröster (University of Edinburgh) as part of Cosmolog y Talks\n\n\nAbstract\nTilman tells us about his recent work combining KiD S cosmic shear measurements and Planck measurements of the thermal Sunyaev Zeldovich (tSZ) effect from the cosmic microwave background scattering of f hot gas in galaxy clusters and galaxy groups. The long term goal is to u se cross-correlation of shear and the tSZ effect to help constrain (or ess entially measure) baryon feedback and thus push to smaller scales.\n\nIn t his work\, they don't push to smaller scales\, partially because doing so would require many more careful checks and partially because Planck's beam isn't small enough to make it worthwhile. However they still gain approxi mately two times tighter constraints in the Ωm vs σ8 plane compared to s hear alone because of the additional information available in tSZ about wh ere matter clusters\, and what the baryons are actually up to.\n\nThe resu lts themselves are awesome (error bars shrinking by a factor of two is imp ressive enough) but also are a great proof of concept that we can measure baryon feedback like this (and don't have to necessarily predict it entire ly from first principles). \n\nWith CMB Stage 4 beam sizes and sky coverag e\, it will be fascinating to see what can be done with this method...\n\n Tilman: https://tilman.troester.s pace/
\nPaper: https://a rxiv.org/abs/2109.04458\n\n
\n\n[00:00] Shaun's intro\n\n[00:46] Summary overview by Tilman\n\n[02:04] What two things do you want people to remembe r about this talk?\n\n[02:56] More background detail on why this is being done now\n\n[07:13] < a href="https://youtu.be/OsX5PNxnkl4?t=433">Details of what was done in th e paper\n\n[10:02] Q&A on the Cosmic Infrared Background importance in this work\n\n[11:33] Usage of data from KiDS (weak le nsing survey designed to optimize for gravitational lensing cosmology\; fu ll overlap with VIKING infrared survey)\n\n[13:11] Plot of measured cross-correlation as angular po wer spectrum between KiDS-1000 and Planck data\n\n[13:55] Modelling\n\n[16:59] HMx paper 2005.00009 hydrodynamical halo mod el for weak-lensing cross-correlations\n\n[20:08] Applying the model to the data\n\n[22:40] Joint analysis with cosmic she ar\; Fig. 5\, 6\, 9 from paper\n\n[30:01] Systematics and results plots\; Fig. 3\, 7 from paper\n\n[37:03] Baryon feedback - intrinsic alignment interaction\n\n[42:21] Where to next?\n\n[43:46] What current cosmology work is particularly under- appreciated by the community?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/42/ END:VEVENT BEGIN:VEVENT SUMMARY:Charles Dalang (University of Geneva) DTSTART:20211124T050000Z DTEND:20211124T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/43 DESCRIPTION:Title: The 4.9σ dipole anisotropy tension *might* be astrophysical redsh ift evolution\nby Charles Dalang (University of Geneva) as part of Cos mology Talks\n\n\nAbstract\nCharles tells us about his recent work with Ca mille Bonvin on the dipole anisotropy tension. \n\nWe expect there to be d ipoles in most observables because of our motion through the (statisticall y) homogeneous and isotropic universe. However\, there appears to be a 4.9 σ tension between the magnitude of the dipole as measured from the CMB an d as measured from quasars in the local-ish universe.\n\nCharles and Camil le have looked at the redshift evolution of the relevant physics that goes into the local-ish prediction for the dipole. They find that if both the magnification bias and the spectral index of the source change with redshi ft\, the naive expectation for the magnitude of the dipole\, given a parti cular velocity can change.\n\nTherefore\, they re-derive an alternative fo rmula that is explicitly redshift dependent and more easily applied direct ly to redshift dependent observations\n\nThey look at a sample of quasars observed by eBOSS to see how the relevant quantities change with redshift. They do change and Charles and Camille show that *if* the larger observed sample of quasars did have the same redshift dependence then the tension would be substantially reduced.\n\nIt is more difficult to measure the ful l redshift dependence of the larger quasar sample used to measure the dipo le as they haven't all been measured with one telescope/survey. It is uncl ear what the actual tension would be between theory and observation were o ne to be able to take the effect C&C point out into account.\n\nTime will tell with more detailed and larger surveys...\n\nCharles: https://cosmology.unige.ch/users /charles-dalang\n\nPaper: h ttps://arxiv.org/abs/2111.03616\n\n
\n\n[00:00] Shaun's introduction\n\n[00:58] Charles' introduction\n\n[01:53] Two simple things to take away from the talk\n\n[02:36] What is the background?\n\n[05:05] Source number count kinematic dipole\n\n[06:15] Theory\n\n[10:50] What are the details?\n\n[11:04] Integrating over comoving distance\n\n[1 3:22] Integrating over redshi ft\; Figs. 1 and 2 from paper\n\n[17:32] Redshift evolution\; Figs. 3 and 4\n\n[20:43] Theoretical Prediction\; Fig. 6 \n\n[22:25] Playing around\; Figs. 7 and 8\n\n[29:31] Conclusions\n\n[30:33] What comes next?\n\n[32:55] What is under-appreciated by the cosmology community as a whole?\ n LOCATION:https://researchseminars.org/talk/CosmologyTalks/43/ END:VEVENT BEGIN:VEVENT SUMMARY:Dillon Brout\, Adam Riess\, Dan Scolnic (Harvard Smithsonian Cente r for Astrophysics\, Johns Hopkins U\, Duke U) DTSTART:20211209T050000Z DTEND:20211209T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/44 DESCRIPTION:Title: SH0ES | H₀ = 73.0 ± 1.0 km s⁻¹ Mpc⁻¹\nby Dillon Brout \, Adam Riess\, Dan Scolnic (Harvard Smithsonian Center for Astrophysics\, Johns Hopkins U\, Duke U) as part of Cosmology Talks\n\n\nAbstract\nDillo n Brout\, Adam Riess and Dan Scolnic talk about the latest SH0ES measureme nt of the Hubble parameter\, making use of the new Pantheon+ supernovae da ta set.\n\nThe measurement accuracy has reached ± 1.0 km s⁻¹ Mpc⁻¹\ , and they analysed the data in 67 different possible ways and every time reach a result that is in significant tension with Planck + ΛCDM. Their b aseline analysis\, the one with the best χ² with the fewest free paramet ers\, is now in 5σ tension\, on its own\, with Planck.\n\nIt isn't clear where the solution to the Hubble tension will come from\, but the fact tha t all local measurements of H₀ come in above Planck\, and that the most accurate measurement is now in 5σ tension is very interesting. It's worth also noting that the prediction from the early universe + ΛCDM doesn't r ely uniquely on Planck. Other CMB experiments give the same small value\, and even just Big Bang Nucleosynthesis and local Baryon Acoustic Oscillati on measurements\, combined with ΛCDM give a small value of H₀. \n\nSo\, if this isn't evidence of new physics in cosmology\, it will be a very st range series of errors that is causing it.\n\nTalk video\n\nDillon: h ttp://djbrout.github.io/
\nAdam: https://www.stsci.edu/~ariess/
\nDan: https://scholars.duke.edu/person/dscolnic
\n\nThe paper: https://arx iv.org/abs/2112.04510\n\n
\n\n[00:00] Shaun's introduction\n\n[01:06] Adam's introduction\n\n[02:36] Dan and Dillon's additional thoughts\n\n[03:21] Two things to take away from the pa per(s) (Adam & Dan)\n\n[05:04] Shaun's intro for diving into the details\n\n[05:21] Pantheon+ Overview: 7 Papers Improving u pon every major facet of Type Ia SN Cosmology (Dan)\n\n[08:14] The Pantheon+ Compilation of SNe (Di llon)\n\n[11:12] SH0ES 2021 details: First Major Update Since 2016 (>1000 orbits HS T) (Adam)\n\n[12:53] SH0E S Distance Ladder Data Sources (Adam)\n\n[17:59] New Cepheid Measurements (Adam)\n\n[19:11] PSF Photometry\, Artificial st ars in pipeline measure backgrounds (Adam)\n\n[19:34] Photometry Validation Tests (Adam)\n\n[2 0:48] Baseline Fit: 3200 Cep heids\, 300 SN\, non-diagonal covariance - 5 free params (Adam)\n\n[22 :29] Baseline Fit: H0=73.04 ± 1.04 km s⁻¹ Mpc⁻¹\, w/ systematics\n\n[24:50] Baseline Fit: Geometric anchor consistency (Ada m)\n\n[26:57] Baseline F it Residuals vs Background/Crowding (Adam)\n\n[28:51] How to: Simultaneous H0 and H(z) (Adam\, Dil lon-public code will be available)\n\n[32:13] Analysis Variants: 12 categories\, 67 variants\, bif urcations\, extensions\, etc (Adam)\n\n[36:12] SH0ES Error Budget (Adam)\n\n[37:00] Main Conclusions\, Sum mary of new details (Adam)\n\n[37:45] Additional thoughts and discussion (Dan\, Ad am)\n\n[41:41] Where to next? (All)\n\n[46:14] What do you think is the solution to the Hu bble tension?(All)\n\n[50:28] What do you think is under-appreciated by the cosmol ogy community? (Adam\, Dan)\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/44/ END:VEVENT BEGIN:VEVENT SUMMARY:Paco Villaescusa (Simons Foundation) DTSTART:20220110T050000Z DTEND:20220110T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/45 DESCRIPTION:Title: CAMELS - Data Release & Series Introduction\nby Paco Villaescu sa (Simons Foundation) as part of Cosmology Talks\n\n\nAbstract\nThis is t he first video in a series of videos covering research that the CAMELS gro up have done. CAMELS are applying machine learning to cosmology\, using a suite of 1000s of simulations to train neural networks\, see what the netw orks learn and then try to unveil what it learned in a way we mere humans can understand.\n\nThis video does a brief intro to CAMELS as well as the data release (and how to access the data).\n\nCAMELS: https://www.camel-simulations.org/
\nTalk video: https://youtu.be/6Vgc72a_VpY
\nPaper: https://arxiv. org/abs/2201.01300\n\nCAMELS talk at Cosmology from Home: https://www.youtube.co m/watch?v=NxR_kDlHhGM&\;t=0s
\nPlaylist of CAMELS video series: https://www.youtube.com/playlist?list=PLvy7h0l2rJHq03inVPqYnC3llK t0IwwLT\n\n
\n\nIndex to Key Parts of the Talk\n\n [00:00] Shaun's introduction t o the 8-video series\n\n[01:02] What is CAMELS?\n\n[01:39] What can CAMELS do that normal cosmology can't?\n\n[03:10] Getting into the details (simu lations\, algorithms\, code\, parameters)\n\n[05:25] CAMELS in relation to IllustrisTNG\, SIMBA\n\n[06:31] Accessing the d ata\n\n[07:22] Technical documentation\n\n[08:00] Using Binder\n\n[08:25] Machine learning tutorials\n\n[09:34] Terminology definitions\n\n[11:44] Using Jupyter Notebook example\n\n[13:32] < a href="https://youtu.be/6Vgc72a_VpY?t=812s">What's been done up to now?\n\n[14:45] Future directi ons\n\n[16:43] How to g et involved\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/45/ END:VEVENT BEGIN:VEVENT SUMMARY:Paco Villaescusa (Simons Foundation) DTSTART:20220111T050000Z DTEND:20220111T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/46 DESCRIPTION:Title: Cosmology with a single galaxy!? (CAMELS)\nby Paco Villaescusa (Simons Foundation) as part of Cosmology Talks\n\n\nAbstract\nPaco tells us about how CAMELS have used machine learning to be able to predict\, wit h a single galaxy's properties\, the value of Ωm used to simulate the gal axy. \n\nThis is fascinating and if a real physical effect has some far-re aching consequences.\n\n- We might one day be able to learn cosmological p arameters by studying the Milky Way
\n- Running a hydrodynamical simula tion with the wrong Ωm would mean\, in principle\, that you'll never repr oduce the exact properties of a galaxy correctly.\n\nCAMELS: https://www.camel-simulations.org/
\nTalk video: https://youtu.be/4Afj qEj_MaI
\nPaco: h ttps://franciscovillaescusa.github.io/
\nPaper: https://arxiv.org/abs/2201.02202\n\nCAMELS ser ies overview: https://www.youtube.com/watch?v=6Vgc72a_VpY&\;t=0s
\nPlaylis t of CAMELS video series: https://www.youtube.com/playlist?list=P Lvy7h0l2rJHq03inVPqYnC3llKt0IwwLT\n\n
\n\nIndex to Key Part s of the Talk>\n\n[00:00] Shaun's intro\n\n[01:06] Paco's introductory comments\n\n[01:41] What questions were you trying to answer?\n\n[02: 21] Getting into the details \n\n[04:17] Training the neural network and testing\n\n[05:56] How correlated are the error bars?\n\n[06:50] Does it work for other parameters bes ides Ωm?\n\n[07:17] Doe s this really work for all galaxies?\n\n[09:10] The galaxy properties that are responsible for thi s result\n\n[16:17] What happens if you train on Illustris and test on SIMBA?\n\n[18:07] What about environmental depende nce?\n\n[20:14] Conclus ions and what should the cosmology community take away from this?\n\n[ 20:54] What would you want to discuss with other experts?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/46/ END:VEVENT BEGIN:VEVENT SUMMARY:Jay Wadekar (Institute of Advanced Study) DTSTART:20220112T050000Z DTEND:20220112T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/47 DESCRIPTION:Title: Galaxy cluster mass estimates improved with AI (CAMELS)\nby Ja y Wadekar (Institute of Advanced Study) as part of Cosmology Talks\n\n\nAb stract\nJay tells us about how he has used the CAMELS suit of simulations to improve upon existing galaxy cluster scaling relations (i.e. trends we use to measure cluster masses using observational probes). \n\nOne example is using the concentration of ionised gas in a cluster to add a little bi t more precision to a Sunyaev Zeldovich effect - mass scaling relation. Th e value of the concentration makes a small change to the prediction.\n\nJa y specifically uses symbolic regression (or similar algorithms) to find ex pressions that link the properties of interest (e.g. mass\, concentration and SZ effect)\, thus allowing us as human beings to also gain some intuit ion from what the machine finds.\n\nJay: https://jaywadekar.github.io/
\nPaper: https://arxiv.org/abs/2201.01305
\nTalk video : https://youtu.be/w_ohkLYMSzs\ n\nCAMELS playlist: https://www.youtube .com/watch?v=6Vgc72a_VpY&\;list=PLvy7h0l2rJHq03inVPqYnC3llKt0IwwLT&\ ;t=0s\n\n
\n\n[00:00] S haun's Intro\n\n[00:59] J ay's opening comments\n\n[01:48] What is the motivation for this work?\n\n[03:17] Comparison of Machine Learning approache s\, starting with deep neural networks\n\n[03:44] Symbolic regression overview\n\n[05:40] How symbolic regression was used in this work\n\n[08:16] Question about the 25 Mpc box size in CAMELS\n\n[11:01] Is the result robust w.r.t. feedback pres criptions?\n\n[13:02] Im proving the domain of validity of scaling relations\n\n[14:59] Summary and takeaway\n\n[16:01] What would you like to talk about with other experts?\n\n[16:43] Application to other scaling relations?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/47/ END:VEVENT BEGIN:VEVENT SUMMARY:Andrina Nicola (Princeton University) DTSTART:20220113T050000Z DTEND:20220113T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/48 DESCRIPTION:Title: Electron density breaks baryon-cosmology degeneracy (CAMELS)\n by Andrina Nicola (Princeton University) as part of Cosmology Talks\n\n\nA bstract\nAndrina tells us about her work using CAMELS and machine learning to constrain baryon feedback using the electron density power spectrum. \ n\nThe electron density is not itself an observable thing\, but it is a go od proxy for observable things like the thermal Sunyaev Zeldovich effect a nd Fast Radio Burst dispersion (or they are good proxies for the electron density).\n\nAndrina is able to get nice constraints on baryon feedback an d cosmological parameters within the CAMELS simulations. This sort of obse rvational probe of baryon feedback is going to be an important tool for co smologists if we want to use smaller scales to do cosmology\, and the sort of connections spotted by Andrina and CAMELS will be valuable for improvi ng these probes.\n\nAndrina: https://www.astro.princeton.edu/~anicola/
\nPaper: https://arxiv.org/abs/2201.04142
\nVideo of talk: https://youtu.be/D _CLangkIDE\n\nCAMELS playlist: https://youtu.be/D_CLangkIDE& amp\;list=PLvy7h0l2rJHq03inVPqYnC3llKt0IwwLT\n\n
\n\n[00:00] Shaun's intro\n\n[00:51] Andrina's overview comments\n\n[ 01:40] What is the motivatio n for this work?\n\n[03:44] Getting into the details\n\n[04:03] Constraining cosmology & baryon physics from 2pt-functions (X-ray\, tSZ\, FRBs)\n\n[04:44] How well can the electron density power spectrum constrain both c osmology and baryonic feedback?\n\n[05:32] Simulations (IllustrisTNG and SIMBA)\n\n[06:35] Plots of the electron power spe ctra from IllustrisTNG & SIMBA simulations (Fig. 1 in paper)\n\n[08:03 ] Baryon fraction as predict or of feedback (Fig. 2)\n\n[09:24] Forecasting constraints (Fig. 3 top panels)\n\n[11:10] Robustness of constraints to sub grid physics (Fig. 3 bottom panels)\n\n[13:37] Q&A on a common theme among several of the speakers \n\n[14:53] Summary\ n\n[16:57] Comments on samp le variance in CAMELS\n\n[17:18] Lingering questions and what would you like to discuss with othe r experts?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/48/ END:VEVENT BEGIN:VEVENT SUMMARY:Leander Thiele (Princeton University) DTSTART:20220114T050000Z DTEND:20220114T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/49 DESCRIPTION:Title: Spectral distortions will measure baryon feedback at % level (CAME LS)\nby Leander Thiele (Princeton University) as part of Cosmology Tal ks\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/49/ END:VEVENT BEGIN:VEVENT SUMMARY:Leander Thiele (Princeton University) DTSTART:20220114T050000Z DTEND:20220114T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/50 DESCRIPTION:Title: Spectral distortions will measure baryon feedback at % level (CAME LS)\nby Leander Thiele (Princeton University) as part of Cosmology Tal ks\n\n\nAbstract\nLeander tells us about work using CAMELS simulations and neural networks to forecast how well future spectral distortion measureme nts will be able to constrain baryon feedback. The answer is "very well" a s it seems the measurements of PIXIE would give even % level measurements of some feedback mechanisms.\n\nLeander: https://phy.princeton.edu/people/leander-thiele
\nPaper: https://arxiv.or g/abs/2201.01663
\nVideo of talk: https://youtu.be/u2tEG1nLwV8\n\nCAMELS playlist: https ://youtu.be/6Vgc72a_VpY&\;list=PLvy7h0l2rJHq03inVPqYnC3llKt0IwwLT\n \n
\n\n[00:00] Shaun's intr o\n\n[00:58] Leander's ov erview comments\n\n[01:47] Motivation for this work: baryonic physics is an impediment to cosmolog y understanding\, e.g.\, huge uncertainty on baryonic feedback mechanisms\ , primarily due to AGN and SN\n\n[02:22] Spectral distortions\n\n[03:51] CAMELS feature of small simulation boxes\n\n[ 04:39] The thermal Sunyaev-Z el'dovich effect\; parameter dependence\n\n[06:25] Forecast constraints\n\n[09:47] Conclusions and takeaways for the cosmo logy community\n\n[10:25] To-Do follow-up\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/50/ END:VEVENT BEGIN:VEVENT SUMMARY:Pablo Villanueva Domingo (Instituto de Física Corpuscular) DTSTART:20220117T050000Z DTEND:20220117T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/51 DESCRIPTION:Title: Weighing the Milky Way with AI (CAMELS)\nby Pablo Villanueva D omingo (Instituto de Física Corpuscular) as part of Cosmology Talks\n\n\n Abstract\nPablo talks about an actual observational result from CAMELS\, t he measurement of the masses of the Milky Way and Andromeda. The results a re in agreement with other methods we've used to measure the masses of the se galaxies.\n\nPablo: https://pablov d.github.io/
\n\nPaper: https://arxiv.org/abs/2111.14874
\n\nVideo of talk: https://youtu.be/yGdcBrYfs8k\n\nCAMELS playlis t: https://youtu.be/6Vgc72a_VpY&\;list=PLvy7h0l2rJHq03inVPqYn C3llKt0IwwLT\n\n
\n\nIndex to Key Parts of the Talk \n\n[00: 00] Shaun's intro\n\n[00:4 6] Pablo's overview comments< /a>\n\n[01:59] Weighing Dark Matter Halos\n\n[03:04] Is the Milky Way big enough that the baryonic/dark matter ratio is expect ed to be the same as on a cosmological or galaxy cluster scale?\n\n[05 :37] Halos as graphs\n\n [06:32] Why graph neural net works? NN type depends on data structure\n\n[07:55] Inferring halo masses in IllustrisTNG\n\n[ 09:20] Cross testing in SIMB A\n\n[10:10] Application to the Milky Way and Andromeda\n\n[10:50] Inferring the MW and M31 masses (Fig. 1 of paper)\n \n[14:10] Conclusions\n\ n[16:07] Lingering questions and what would you like to discuss with other experts?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/51/ END:VEVENT BEGIN:VEVENT SUMMARY:Lucia Perez (Arizona State University) DTSTART:20220118T050000Z DTEND:20220118T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/52 DESCRIPTION:Title: Fixing CAMELS biggest flaw (small box sizes) with semi-analytic mo dels\nby Lucia Perez (Arizona State University) as part of Cosmology T alks\n\n\nAbstract\nLucia tells us about her work with CAMELS trying to ov ercome the biggest barrier CAMELS faces\, small box size. It might never b e possible to run 1000s of large volume hydrodynamical simulations simply because the hierarchy of scales is too big (baryon feedback happens on sma ll scales\, overcoming sample variance requires very large boxes). \n\nThe refore\, to get many many simulation boxes\, with baryonic effects in them one option is semi-analytic models. This is what Lucia has and is doing a nd what she discusses in the video...\n\nLucia: https://isearch.asu.edu/profile/2606833\n\nPap er: Constraining cosmology with machine learning and galaxy clustering: the CAMELS-SAM suite [2204.02408]
\n\nTalk video: https://you tu.be/sx0RCW2p4eU\n\nCAMELS playlist: https://youtu.be/6Vgc7 2a_VpY&\;list=PLvy7h0l2rJHq03inVPqYnC3llKt0IwwLT\n\n
\n\n[00:00] Shaun's intro\n\n[01:15] Lucia's overview comments \n\n[01:49] The massiveness of this work\; why it's still not feasible to do this on a much larger sca le\n\n[02:12] Video of a simulation\n\n[02:37] H ow this work fits within the rest of the project\n\n[03:53] Why do this?\n\n[05:34] Science questions\n\n[08:23] Getting to smaller scales\; neura l networks\n\n[09:14] Ta ke-away 1: use more than just two-point statistics\n\n[10:38] Issue about summary statistics\n \n[12:49] Discussion on vari ous meanings of voids\n\n[13:33] How does each statistic perform alone? Or all together?\n\n[1 5:50] Take-away 2: SAM (semi -analytic model) galaxy clustering measures cosmology well\n\n[16:49] Take-away 3: with a SAM\, c lustering still feels astrophysics\n\n[18:38] Conclusions\n\n[19:37] The big picture implications and questions...\n \n[22:28] What would you li ke to discuss with other experts?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/52/ END:VEVENT BEGIN:VEVENT SUMMARY:Sultan Hassan (Center for Computational Astrophysics\, Flatiron In stitute) DTSTART:20220211T050000Z DTEND:20220211T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/53 DESCRIPTION:Title: Full non-linear density fields without simulations! (HIFlow/CAMELS )\nby Sultan Hassan (Center for Computational Astrophysics\, Flatiron Institute) as part of Cosmology Talks\n\n\nAbstract\nSultan tells us about his work training neural networks on the neutral hydrogen density fields in the CAMELS simulations. \n\nHe uses a process known as normalising flow s to find a mapping between the non-linear\, very non-Gaussian 2D projecte d density field and a different Gaussian field. Once this mapping is found \, the idea is that one can do full statistics on the non-linear field\, b y sampling from the Gaussian one. The bold ambition is to use this process to reduce the need for running computationally expensive hydrodynamical s imulations - making it more feasible to get precise cosmological constrain ts from future surveys.\n\nIt's early days in the project\, but the result s are already promising as the model is able to generate density fields th at match both the histogram of density values and the power spectrum (as w ell as the scatter in both functions) reasonably well.\n\nSultan: https://sultanier.wixsite.com/webs ite\n\nThe Talk: https://youtu. be/wDRd7MojD3I\n\nThe Paper: https://arxiv.org/abs/2110.02983\n\nCAMELS playlist: https: //www.youtube.com/playlist?list=PLvy7h0l2rJHq03inVPqYnC3llKt0IwwLT\n\n CAMELS intro: h ttps://www.youtube.com/watch?v=6Vgc72a_VpY\n\n
\n\n[00:00] Shaun's intro\n\n[01:29] Sultans's overview comments\n\n[02 :26] At what point in traini ng does the model reach a saturation point?\n\n[02:57] What questions were you trying to answer an d why are they important?\n\n[04:10] The main idea of this work\n\n[05:02] Details on how it's done\; addressing the probl ems\n\n[07:38] Details o f the results\; Figure 2 from the paper\n\n[10:21] Power spectra and PDFs over the testing set\; F igure 3\n\n[11:05] Norma lizing flow\n\n[12:58] A dditional details on the power spectra slide\n\n[15:31] Conditioned on Cosmology slide\, Figure 5\ ; comparison between HIFlow and CAMELS\n\n[16:31] Accuracy over all testing set\, R^2 > 90%\, Figu re 7\n\n[18:08] Take-aw ays for the rest of the cosmology community from this work\n\n[19:37] What would you like to disc uss with other experts inside or outside of CAMELS?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/53/ END:VEVENT BEGIN:VEVENT SUMMARY:Dillon Brout (Harvard Smithsonian Center for Astrophysics) DTSTART:20220301T050000Z DTEND:20220301T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/54 DESCRIPTION:Title: Pantheon+: Cosmology results & Dust\nby Dillon Brout (Harvard Smithsonian Center for Astrophysics) as part of Cosmology Talks\n\n\nAbstr act\nDillon Brout tells us about the recent Pantheon+ supernovae catalogue and cosmology results. The cosmology results are excellent\, including a factor of two improvement in the "figure of merit" compared to the previou s Pantheon result (essentially a halving of error bars). \n\nHowever\, the results aren't going to help anyone looking for a clue for a source of ne w physics. The supernovae themselves appear to follow the ΛCDM model very closely. If one anchors them to Planck\, or to the SH0ES Cepheids\, eithe r way\, one finds tight constraints on beyond ΛCDM parameters like an equ ation of state "w" or evolution of an equation of state "w_a".\n\nThere is of course the baffling Hubble tension among all of this\, and that is ver y clearly visible here. Both the Planck+Pantheon and the SH0ES+Pantheon re sults match up with ΛCDM\, but at different values of H0. Any solution to the H0 tension that involves beyond ΛCDM evolution in the late-universe appears to be heavily constrained.\n\nThe most interesting part of this ta lk (for me) was actually the introduction in the answer to "what needed to be done before this analysis could happen" (in fact\, this makes up the l argest portion of the talk!). Dillon goes into quite a bit of detail about an earlier paper he wrote with Dan Scolnic\, examining the affects of dus t on supernovae observations. It appears that three of the most important mysteries in SN analysis were all explainable by the same dust affect and Dillon explains why here.\n\nTalk video: https://youtu.be/lVN1-FcCBDc\n\nDillon: https://djbrout.github.io/\n\nPantheon+ cosmology paper: https://arxiv.org/abs/2202.040 77\n\nEffects of dust on supernovae paper: https://arxiv.org/abs/2004.10206\n\n
\n\nIndex t o Key Parts of the Talk\n\n[00:00] Shaun's intro\n\n[00:57] Dillon's introductory comments\n\n[01:23] Two things for people to remember from this talk ?\n\n[05:14] The motivat ional and the logistical aspects for this work?\n\n[08:41] Structure formation work based on super novae peculiar velocities\n\n[10:17] Why wasn't some of this work done in 2018? Why now?\n\n[1 1:33] What questions were un solved that you wanted to address? Figure 4 from the 2202.04077 paper\ n\n[12:03] 3 Lingering Myste ries Central to SNIa Cosmology\n\n[12:45] 1. What drives the observed SN colors and color/luminosi ty relations?\n\n[14:14] 2. What drives the underlying residual scatter of standardized SNe Ia?\n\n[15:45] 3. What's drivi ng the evidence for additional standardization?\n\n[17:13] Cepheid calibration question relating to the number of SN used in this work\n\n[19:19] The SH0ES measurement: host galaxy demographics\ , calibrator set of hosts\, distance ladder rung\n\n[20:33] The "aha moment"\n\n[21:04] Dust can be the solution to all three mysteries!\n\n[23:08] We can forward the whole sample to learn about SN/Host physics\n\ n[25:10] The mass step is a consequence of differing dust properties for hosts of different masses\n\n[25:35] Dust attenuati on as a function of host galaxy properties\n\n[27:06] Dust is the solution!\n\n[27:38] Predictions from the model\n\ n[28:13] What are the cosmo logical results in this paper? Figures 4\, 6\; It's important to use the covariance matrix\n\n[29:43] Constraints on LCDM\, Figure 8\; Consistency with other probes\n \n[32:02] The data set with and without SH0ES\; Figure 9\n\n[32:34] Measuring w_a\, the evolution of dark energy\; Figure 10 \n\n[34:50] Including B AO\; Figures 11\, 12\n\n[35:31] What's next? DES\, LSST\, Machine Learning\n\n[38:36] Comments on the cosmology communit y follow-up to this work\n\n[40:49] What current cosmology work do you think is particularly unde r-appreciated?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/54/ END:VEVENT BEGIN:VEVENT SUMMARY:Alexandra Amon & Naomi Robertson (University of Cambridge) DTSTART:20220324T050000Z DTEND:20220324T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/55 DESCRIPTION:Title: Lensing & clustering are consistent. Small scales are tough but ke y to solving S8\nby Alexandra Amon & Naomi Robertson (University of Ca mbridge) as part of Cosmology Talks\n\n\nAbstract\nAlex Amon and Naomi Rob ertson talk about their recent work analysing all of the Dark Energy Surve y (DES)\, the Hyper Suprime Cam survey (HSC)\, and the Kilo Degree Survey (KiDS) and the Baryon Oscillation Spectroscopic Survey (BOSS). In particul ar they look to see whether the three lensing surveys (DES\, HSC and KiDS) are consistent with the clustering of galaxies in BOSS.\n\nConsistency ch ecks are always good just for their own sake\, but this has particular rel evance in the context of the S8 tension\, as the lensing surveys provide t he strongest evidence of this tension.\n\nThey find that the lensing surve ys are (broadly) consistent with each other and are then also consistent w ith the clustering in BOSS. When restricting to larger scales\, they also don't find evidence for a different cosmology to Planck. When they include smaller scales there is a strong tension between the lensing/clustering p robes and the Planck cosmology (i.e. the S8 tension).\n\nTakeaways are tha t the local probes of matter appear to be consistent with each other and t he S8 tension is best probed by smaller scales. Unfortunately this is also where baryonic effects dominate so we need more data constraining them an d improved modelling to make further progress.\n\nAlex: https://amonalexandra.com/\n\nNaomi: https://www.ast.cam.ac.uk/peo ple/naomi.robertson\n\nTalk video: https://youtu.be/4gjlNyJ0AKY\n\nThe paper: https://arxiv.org/abs/2202.07440\n\n
\n\nInd ex to Key Parts of the Talk\n\n[00:00] Shaun's intro\n\n[01:15] Alex and Naomi's introductory comments\n\n[02:12] Two things for people to remember f rom this talk\n\n[03:43] The motivation for this work\n\n[06:24] State of the art lensing data\n\n[07:20] Challenges with small-scale modeling \n\n[10:00] Clustering and L ensing 101\n\n[11:41] Da ta: Fig. 2 top panel and Fig. 3 from paper\n\n[14:12] Source sample: Lensing from DES-Y3\, KiDS-10 00\, & HSC-Y1: Table 1 from paper and Fig. 2 all panels\n\n[15:50] Consistency of Lensing Measurem ents: Fig. A1\, Table A1\n\n[18:22] DarkEmulator and HOD\n\n[20:15] Joint Lensing and Clustering Fits\n\n[22:39] Small Scale Modelling Systemat ics: Fig. 4\n\n[30:10] Consistency of Clustering and GGL\n\n[30:50] Consistency of Clustering and GGL: Large Scales: Fig. 6 left panel\n\n[32:55] Consistency of Clustering and GGL: All Scales: Fig. 6 right panel\n \n[34:18] Cosmology vs. sma ll-scale systematics: Fig. 7\n\n[37:42] Summary\n\n[38:40] What's next?\n\n[41:58] What current cosmology work do you think is particularly und er-appreciated?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/55/ END:VEVENT BEGIN:VEVENT SUMMARY:Colin Hill\, Adrien La Posta\, and Evan McDonough (Université Par is-Saclay\, Columbia University\, University of Winnipeg) DTSTART:20220410T060000Z DTEND:20220410T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/56 DESCRIPTION:Title: The CMB's mixed messages on early dark energy... &\; theory's r esponse\nby Colin Hill\, Adrien La Posta\, and Evan McDonough (Univers ité Paris-Saclay\, Columbia University\, University of Winnipeg) as part of Cosmology Talks\n\n\nAbstract\nColin Hill\, Adrien La Posta\, and Evan McDonough tell us about the state of play with early dark energy (EDE). Th ey cover both observation\, primarily the CMB\; and fundamental physics mo dels that might generate EDE phenomenology.\n\nColin gives an intro to EDE \, the Hubble tension\, how the CMB is sensitive to EDE\, and EDE models\, and then shows how the observational evidence for/against EDE from the CM B is... curious. \n\nThe Atacama Cosmology Telescope (ACT) + large scales of Planck/WMAP appear to favour\, or even detect(!?)\, EDE at more than 3 sigma\, more or less "solving" the Hubble tension (if you ignore large sca le structure\, which you shouldn't!). However\, the full Planck data sees no evidence at all\, even excluding Hubble tension solving values of EDE a t about 3 sigma. ACT+Planck also excludes EDE\, because small scale Planck is just so constraining that any ACT preference is washed out\; there's j ust so much more statistical information in Planck small scales!\n\nAdrien then talks about how one can eliminate at least one possible CMB systemat ic via using the ratio of power spectra. When doing this there is still a Hubble tension\, and the results are completely consistent with convention al CMB analyses (albeit with larger error bars because some info is thrown out when taking this ratio). He then covers the same analysis as Colin's ACT analysis\, but this time with the South Pole Telescope (SPT). SPT also allows large EDE amplitudes\, but isn't constraining enough to either fav our or rule them out.\n\nThe small additional constraining power of SPT do es mean though that ACT+SPT+WMAP seems to almost conclusively detect EDE ( or some equivalent phenomena). It makes me think that *if* Planck didn't e xist\, we'd be almost convinced this is *the* answer to where the Hubble t ension is coming from. Unfortunately\, Planck does exist and doesn't see a ny evidence for this at all - suggesting that this is instead either some systematic in ACT\, or a statistical fluke.\n\nSo\, all bets are off\, but this is something to really keep an eye on. ACT will have much more data to say much more about this "within a year" (everything is blind at the mo ment though so nobody knows what the data will point at in the end).\n\nFi nally\, Evan talks about theory space and how one might tackle this myster y of EDE and Hubble tensions and *crucially* large scale structure. He tal ks about a "swampland" motivated principle that might allow the mass of da rk matter to be influenced by the early dark energy\, meaning that the "S8 tension" would not be made worse by early dark energy\, but possibly even made better. Coupling EDE to dark matter might also help explain why any EDE transition happens to happen close to when the CMB is formed\, maybe.. . time will tell.\n\nThe talk video: https://youtu.be/T15WSiHdOFI
\n\nAdrien: https://inspirehep.net/authors/1889152
\nA drien's paper: https://arxiv.or g/abs/2112.10754
\n\nColin: http://user.astro.columbia.edu/~jch/
\nColin's paper: https://arxiv.org/abs/2109.04451
\n\nEvan: https://www. evanmcdonoughphysics.com/
\nEvan's paper: https://arxiv.org/abs/2112.09128
\n\nColin's earl ier video on EDE and large scale structure: https://www.youtube.com/watch?v=5JRHFGuPAV8
\n\n
\n\nIndex to Key Parts of the Talk \n\n[0:00:00] Shaun's intro\n\n[0:01:05] Colin's introductory comments< /a>\n\n[0:02:13] Two things for people to remember from this talk\n\n[0:03:24] The background and context for this work\; th e Hubble Situation\n\n[0:06:01] ACT Data Release 4: significant improvement upon Planck\, esp . on small scales\n\n[0:06:54] ACT DR4: foreground-marginalized CMB power spectra\n\n[0:08:16] ACT DR4 Cosmology\n\n[0:0 9:46] Early Dark Energy : motivation - increase CMB-inferred H0\n\n[0:11:28] Importance of the FIRAS measurement\n\n[0:14 :09] EDE: new component - ( pseudo)-scalar field\n\n[0:16:09] EDE: Parameterization\n\n[0:16:51] EDE model maintains good fit to CMB power spectrum data with higher H0\n\n[0:17:29] LSS in EDE Model\n\n[0:18:24] EDE in Planck Primary CMB?\n\n[0:19:21] Data set combinations: Planck + BOSS (EFT) + DES/HSC/KiDS (S8)\n\n[0:20:32] Pre-ACT DR4 Summary\n\n[0:21:22] ACT DR4 EDE Analysis\n\n[0:23:53] ACT DR4 EDE Results: Fig. 1 f rom 2109.04451\n\n[0:27:20] Origin of ACT EDE Preference: Figs. 3\, 4 from 2109.04451\n\n[0:29:2 0] ACT DR4 EDE experimenta l and theoretical takeaways\n\n[0:31:53] Adrien's intro to the 2112.10754 paper (SPT-3G)\n\n[ 0:33:30] Two potential sol utions on the CMB side for this tension\n\n[0:34:12] Using observables less sensitive to systema tics\n\n[0:36:58] SPT- 3G results vs Planck\, ACT DR4\, and SH0ES\n\n[0:39:08] Summary of EDE results\n\n[0:39:30] New results from SPT-3G pu blic data: Figs. 1\, 2 from 2112.10754\n\n[0:41:52] Impact of the z_c prior: Fig. 3 from 211 2.10754\n\n[0:43:55] Combi ning with other CMB datasets\n\n[0:45:00] Combining with SH0ES constraint\n\n[0:46:03] Adrien's Conclusions\n\n[0: 49:09] Evan's intro to the 2112.09128 paper\n\n[0:50:28] A recipe for the CMB: CLASS-EDE code on github\n\n[0:51:57] < a href="https://youtu.be/T15WSiHdOFIc?t=3117s">Imprint on Large Scale Stru cture\n\n[0:53:38] EDE and Data\n\n[0:54:36] EDE and Theory\n\n[0:56:28] Extending the model: EDE => EDS\n\n[0:58:07] Punchline\n\n[1:00:00] Into the weeds: What drives the tight const raint on c?\n\n[1:02:34] The power of ACT: Fig. 10 from 2112.09128\n\n[1:04:01] The power of DES-Y3\n\n[1:04:40] < a href="https://youtu.be/T15WSiHdOFIc?t=3880s">Evan's wrap-up\n\n[1:05 :50] Where to next?\n\ n[1:08:10] What current co smology work do you think is particularly under-appreciated?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/56/ END:VEVENT BEGIN:VEVENT SUMMARY:Silvia Manconi (RWTH Aachen University) DTSTART:20220502T060000Z DTEND:20220502T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/57 DESCRIPTION:Title: Planck polarisation beats intensity for dark matter searches at th e galactic centre\nby Silvia Manconi (RWTH Aachen University) as part of Cosmology Talks\n\n\nAbstract\nSilvia tells us about her recent use of Planck satellite data to search for dark matter. She doesn't use the CMB t hough\, instead she is looking for microwave emission from the galactic ce ntre. For her\, the CMB is noise!\n\nIf dark matter decay/annihilation lea ds to electron positron emission then those electrons and positrons would emit microwave light through synchrotron radiation as they travel through the magnetic fields at the galactic centre.\n\nShe found that the polarisa tion signal is a more sensitive probe of this effect than the intensity. T he main theory for why this is is that the observed signal in the polarisa tion has more features (coherent hot and cold spots)\, whereas the expecte d dark matter signal should be more smooth. Whereas both the intensity mea surement and signal should be more smooth. Therefore\, the observed polari sation "cold spots" can best constrain the dark matter signal\, especially close to the galactic centre\, where the dark matter signal should still be strong.\n\nSilvia: https ://silviamanconi.wordpress.com/\n\nPaper: https://arxiv.org/abs/2204.04232\n\nRecorded Talk: https://youtu.be/5lIPLbUyTyw\n\n
\n\nIndex to Key Parts of the Talk\n\n[00:00] Shaun's intro\n\n[00:42] Sil‎via's intro comments on this work\n\n[03 :41] Two things for people t o remember from this talk\n\n[04:43] Motivations for this work\n\n[06:55] Q&A on physics of the DM annihilation and how th e synchotron intensity is relevant\n\n[11:28] What we need to model\n\n[12:19] Q&A involving Fig. S4 from the paper\n\ n[14:19] Q&A involving Fig. S5 top panel\n\n[16:57] Getting into the details: Planck maps processing\, Fig. 1\n\n[21:39] Discussion on the magnetic fields at the galaxy center\n\n[22:59] Magnetic field models\n\n[26:16] Dark matter signal\, Fig. S3\n\n[27:27] Dark matter profile\, Fig. S7\n\n[29:44] Summary plot\ , Fig. 3 right panel\n\n[34:03] Why is polarisation the most constraining?\n\n[37:32] Magnetic field configuration uncer tainty\, Fig. 3 left panel and Fig. 8 left panel\n\n[38:24] What comes next?\n\n[39:28] Fig. S5 top panel\n\n[42:24] Perspectives for follow-up work\n\n[44:10] What c urrent cosmology work do you think is particularly under-appreciated?\ n LOCATION:https://researchseminars.org/talk/CosmologyTalks/57/ END:VEVENT BEGIN:VEVENT SUMMARY:Andrej Dvornik and Constance Mahony (Ruhr University Bochum) DTSTART:20220617T060000Z DTEND:20220617T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/58 DESCRIPTION:Title: The Kilo-Degree Survey goes non-linear. With cosmology constraints !\nby Andrej Dvornik and Constance Mahony (Ruhr University Bochum) as part of Cosmology Talks\n\n\nAbstract\nAndrej Dvornik and Constance Mahony tell us about the Kilo-Degree Survey (KiDS) and their progress at probing the non-linear scales with data from the survey.\n\nConstance talks about her recent paper showing that non-linear halo bias is absolutely necessar y if you want to avoid errors larger than 5σ on the small\, non-linear sc ales.\n\nAndrej takes this and does the analysis on KiDS data to obtain co smological constraints.\n\nConstance: INSPIRE author page\n\nConstance's paper: arxiv.org/abs/2202.01790\n\nAndrej: Personal Website\n\nAndrej's paper: < a href="https://arxiv.org/abs/2210.03110">arxiv.org/abs/2210.03110\n\n
\n\nIndex to Key Parts of the Talk:
\n[00:00] Shaun's intro\n\n[00:56] Constance's overview comments on this work\n\n[ 01:45] Andrej's overview comm ents\n\n[03:12] Two thin gs for people to remember from this talk\; start of Constance's portion of talk\n\n[03:57] Backgro und and context\; details on the Halo Model\; revisiting the assumption of linear halo bias\n\n[06:05] Corrections going beyond linear-halo bias\n\n[06:47] Halo model contributions slide\; eqns (1) in 2202.01790\n\n[07:37] Halo model power spectra\; eqns (2)\n\n[09:07] Beyond-linear halo bias\; eqn (14)\n\n[11:03] Dark Emulator\; Appendix A of p aper\n\n[11:45] Quick int ro about KiDS\n\n[12:38] Cosmology Dependence σ8\; Fig. 1 of paper\n\n[13:58] Q&A on meaning of excess surface density\ n\n[15:24] Cosmology Dependen ce Ωm\n\n[16:02] KiDS ga laxy-galaxy lensing and clustering\; Fig. 3\, main takeaway plot from the paper\n\n[17:52] Stellar Mass Function\; Fig. 4\n\n[18:48] HSC Y1 results with DarkEmulator+HOD (halo occupation distribut ion)\n\n[19:36] Comparis on to DarkEmulator+HOD\; Fig. 5\n\n[25:25] DarkEmulator+HOD Mock Analysis\; Fig. 6\n\n[21:03] DarkEmulator+HOD Results \n\n[21:35] Constance's Summ ary: Beyond-linear halo bias summary\n\n[23:11] Andrej's portion of talk: Two things for people to remember\n\n[24:08] 2x2 point cosmology with SMF (stellar mass function)\n\n[25:24] Halo occupation modelling\n\n[27: 47] Describing the galaxy bi as\n\n[29:29] Further as sumptions in the model\n\n[31:34] Parameters\n\n[33:09] Graphic: How stellar mass correlates with the halo mass\n\n[35 :08] Graphic: Stellar mass f unction\n\n[35:55] KiDS- 1000/DR4\; The data\n\n[38:21] Measurements\n\n[40:37] Results\n\n[42:38] Comparison with other literature\n\n[47:07] Andrej's Summary\n\n[47:39] Some Q&As on where to next\n\n[53:26] What current cosmology work do yo u think is particularly under-appreciated?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/58/ END:VEVENT BEGIN:VEVENT SUMMARY:Jiamin Hou\, Zachary Slepian and Robert Cahn (U of Florida\, LBNL) DTSTART:20220819T060000Z DTEND:20220819T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/59 DESCRIPTION:Title: 7σ (!?) detection of parity violation in the large scale structur e\nby Jiamin Hou\, Zachary Slepian and Robert Cahn (U of Florida\, LBN L) as part of Cosmology Talks\n\n\nAbstract\nJiamin Hou\, Zachary (Zack) S lepian and Robert (Bob) Cahn talk about their very interesting\, recent pa per looking for parity violation in the large scale structure. Cutting to the chase\, they find evidence for it at ~7σ. They also do various system atic tests and none reduce the significance below 4σ.\n\nTantalisingly\, parity violation in the LSS could be related to birefringence in the cosmi c microwave background\, with many models that would produce one\, also pr oducing the other. Avid channel viewers will remember a talk from two year s ago with evidence for exactly that. \n\nAre we seeing the beginnings of evidence for genuine parity violation on cosmological scales\, or are the two hints caused by independent errors?\n\nThis is definitely a space to w atch...\n\nJiamin: h ttps://astro.ufl.edu/directory/jiamin-hou/
\nZack: https://astro.ufl.edu/directory /zachary-slepian/
\nBob: http://phyweb.lbl.gov/~rncahn/www/cahn.html
\n\nTalk recording
\n\nThe paper (resul ts): https://arxiv.org/abs/2206 .03625
\nThe paper (earlier methods): https://arxiv.org/abs/2110.12004
\n\n
\n\nIndex to Key Parts of the Talk\n\n[00:00] Shaun's intro\n\n[00:58] Intro comments on this work (Bob)\n\n[01:55] Two things for people to remember from thi s talk (Zack)\n\n[03:45] The background on parity violation and its applications to cosmology\ n\n[10:31] Cosmological pari ty violation must be from epoch of inflation\n\n[11:20] Parity violation does not conflict with ho mogeneity or isotropy\n\n[12:11] Parity violation with the 4PCF of LSS (Fig. 1 from 2206.03625)\n\n[12:56] NPCFs in the Is otropic Basis\n\n[16:25] Great Find: Yutsis\, Levinson\, & Vanagas (1962)\n\n[17:63] Why is this working happening now an d not earlier? (Zack)\n\n[22:26] N-Point Functions on the GPU with CADENZA\n\n[23:47] Data analysis: 2 samples used - BO SS DR12 LOWZ and CMASS (LRGs) (Jiamin)\n\n[24:39] Two challenges\n\n[25:14] 3 Ways We Estimate the Covariance Matrix\n\n[28:16] Testing the De tection Significance's Robustness\n\n[29:42] Test of Analytic Covariance Matrix (Fig. 7 from 2206 .03625)\n\n[34:38] Q&A: is it possible this is non-isotropy instead of parity violation?\n\n[ 37:46] Impact of Systematic s on Parity-Odd Modes\n\n[41:18] A non-exhaustive list of potential questions\n\n[46:26] What are the next steps?\n\ n[55:32] What current work in cosmology is particularly under-appreciated?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/59/ END:VEVENT BEGIN:VEVENT SUMMARY:Johannes Røsok Eskilt\, Patricia Diego-Palazuelo (U of Oslo\, U o f Cantabria) DTSTART:20220920T060000Z DTEND:20220920T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/60 DESCRIPTION:Title: 2.4σ → 3.6σ\, CMB Birefringence in 2022\nby Johannes Røso k Eskilt\, Patricia Diego-Palazuelo (U of Oslo\, U of Cantabria) as part o f Cosmology Talks\n\n\nAbstract\nJohannes Røsok Eskilt and Patricia Diego -Palazuelo update us on the state of measurements of birefringence in the cosmic microwave background in 2022. The current most popular video on the channel was about a tentative hint of CMB birefringence back in 2020 and much can change in two years.\n\nThe tentative hint is very much still pre sent. Johannes and Patricia are both members of Planck itself and have spe nt the last few years checking for systematics\, taking the effects of EB correlations in the dust into account\, adding WMAP data\, adding addition al frequency maps from Planck\, and checking for a frequency dependence of the signal.\n\nSo far there are no smoking guns saying "oops\, this is wh at is causing the signal"\, so new physics is very much still on the table .\n\nWith the additional Planck maps and WMAP data included\, as well as t ighter modelling of the dust\, the statistical significance has drifted up from 2.4σ two years ago to 3.6σ today\, which is exactly what one would expect if this was a real signal.\n\nThe crucial test of this would be a ground based experiment like ACT\, SPT or BICEP calibrating their misalign ment angle directly with greater accuracy than Planck/WMAP can indirectly and looking directly for an EB signal in the CMB... if they still see some thing that would be extremely interesting!\n\nRecorded talk: https://youtu.be/k9YZiWoFwzg\n\nJohannes: https://w ww.mn.uio.no/astro/english/people/aca/johanres/
\nPatricia: https://inspirehep.net/authors/1 954027\n\nPaper 1: https:// arxiv.org/abs/2201.07682
\nPaper 2: https://arxiv.org/abs/2205.13962\n\n
\n\nIndex to Ke y Parts of the Talk\n\n[00:00] Shaun's intro\n\n[00:49] Summary comments on this work\n\n[02:43] Two things for people to remember from this talk \n\n[03:40] The potential fo r ground-based telescopes in this work\n\n[05:18] What is the significance of this work?\n\n[0 5:52] Getting into the detai ls\n\n[14:00] Consistent results across 4 independent pipelines\n\n[14:31] Results\n\n[15:41] Need to correct for dust EB to obtain unbiased measu rement of birefringence\n\n[18:36] Two independent ways of mitigating the effect of dust EB\n \n[19:24] Where does dust E B come from?\n\n[21:26] Commander sky model as foreground model\n\n[22:58] What did we do next?\n\n[23:36] Q&A if there's a dust EB amplitude p rediction\n\n[25:25] Wh at happens if we include all Planck maps?\n\n[26:24] What is the origin of the signal? (if real)< /a>\n\n[27:12] Signal is co nsistent with being frequency-independent\n\n[28:28] Adding LFI increased the significance\n\ n[29:28] Adding WMAP increa ses the significance\n\n[31:21] The fitting\; Figs. 4\,5 in 2205.13962\n\n[32:24] Miscalibration angles\; Fig. 3 in 2205 .13962\n\n[33:41] Summa ry of Planck plus WMAP analysis\n\n[34:00] Quantifying systematics using NPIPE end-to-end simulat ions\n\n[39:26] FAQ \n\n[42:22] Conclusions \n\n[48:28] What current co smology work is particularly interesting or underappreciated?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/60/ END:VEVENT BEGIN:VEVENT SUMMARY:Richard Easther (University of Auckland) DTSTART:20221026T050000Z DTEND:20221026T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/61 DESCRIPTION:Title: The earliest gravitational structures (just after inflation)\n by Richard Easther (University of Auckland) as part of Cosmology Talks\n\n \nAbstract\nRichard Easther talks about the era immediately after inflatio n. If reheating is delayed then the small perturbations in the density of the universe grow\, just as they do during matter domination in the late u niverse. The growth of non-linear structures during this "early dark age" has not been explored in depth until recently and Richard gives an overvie w of recent work on the topic.\n\nIt turns out that the evolution of struc tures during this era is described mathematically using essentially the sa me equations as a fuzzy dark matter/ultralight dark matter epoch now. This means all the tools developed for fuzzy dark matter are re-usable in this earlier epoch. In fact\, on large enough scales\, even a Newtonian N-body code suffices.\n\nThere are interesting things to explore in models that have existed since inflation became a topic\, one doesn't need to cook up exotic scenarios\, all that is needed is for reheating to not happen insta ntly. In fact\, in units of efoldings\, this early matter domination\, gro wth of structures period of time could even last much longer than the late universe matter dominated phase\, meaning structures have much longer to grow\, and viralise\, and accrete more matter - making them a fascinating thing to study.\n\nTalk recording: https://youtu.be/kPiCZpi1Px4\n\nRichard: https://excursionset.com/about-me\n\nPaper 1: https://arxiv.org/abs/1909.11678
\nPaper 2: https://arxiv.org/ab s/1911.01661
\nPaper 3: https://arxiv.org/abs/2011.13333
\nPaper 4: https://arxiv.org/abs/2110.15109
\n\n
\n Index to Key Parts of the Talk\n\n[00:00] Shaun's intro\n\n[00:43] Richard's summary comments on this work\n\n[03:28] Two things for people to rememb er from this talk\n\n[06:50] Richard's motivation for studying this early matter-dominated field\n\n[15:22] Comments on pa rallels to ultralight dark matter work\n\n[18:32] Getting into the details: Post-Inflationary Uni verse\n\n[19:39] Inflat ion Condensate\n\n[24:04] Paper 1\, 1909.11678\n\n[30:06] Self-gravitating quantum matter\n\n[33:24] Schrodinger-Poisson Equation\n\n[35:24 ] Proof of Concept\n\n[ 38:57] Figure 2 from 1909.1 1678\n\n[39:18] Structu re formation...\n\n[40:27] Cosmic web (simulation)\n\n[41:01] A theorist's playground\n\n[43:05] Developing/adapting new numerical tools\; 1911 .01661\, 2011.1333\n\n[50:44] Simulation\, 2011.13333\n\n[51:34] Biggest smallest simulation\n\n[52:09] cf Press-Schecter\; Zoom-in simulations \, 2110.15109\n\n[56:19] Future Work...\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/61/ END:VEVENT BEGIN:VEVENT SUMMARY:Keir Rogers (University of Toronto) DTSTART:20230122T050000Z DTEND:20230122T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/62 DESCRIPTION:Title: Ultralight dark matter and the S8 tension\nby Keir Rogers (Uni versity of Toronto) as part of Cosmology Talks\n\n\nAbstract\nKeir tells u s about constraints on the fraction of dark matter that could be "ultralig ht" at various masses. \n\nIt seems probable now that one single mass of u ltralight dark matter (ULDM) can't be responsible for all the dark matter\ , but this doesn't mean it can't be a sub-component of the dark matter. Th e structure suppressing properties of ULDM could also have implications fo r the S8 tension\, i.e. maybe a small sub-component of ULDM is what is cau sing the low S8 in local measurements?\n\nThe observational data Keir cons iders are the Planck CMB data and BOSS clustering data.\n\nRecorded talk\n\nKeir: keirkwame.github.io\n\nPaper: 2301.08361\n
\n\nIndex to Key Parts of the Ta lk\n\n[00:00] Shaun's intr o\n\n[00:53] Kier's brief opening comments about his paper\n\n[02:38] Two things for people to remember from this talk\n \n[04:16] What is the motivat ion for this research?\n\n[05:00] Find dark matter by only known interaction - gravity (with ga laxies and intergalactic gas as tracers)\n\n[05:45] Beyond the WIMP: dark matter model space\n\n[08 :12] ULAs are invoked to reso lve so-called CDM "small-scale crisis"\n\n[09:02] "Canonical" 10^-22 to 10^-21 eV ULA DM is ruled o ut\n\n[09:37] Stringy axi ons & the string axiverse\n\n[13:08] Multi-probe approach to detect ULAs\n\n[15:25] Axions are dark matter and dark energy c andidates\n\n[17:13] Sim ulation animations with and without axions\n\n[19:08] S8 tension\n\n[22:46] ULA DM causes scale-dependent suppression in m atter clustering\n\n[26:45] Axions lower S8\n\n[27:50] Lightest axions constrained by CMB\n\n[30:01] Planck 2018 reionisation bump breaks axion de generacies\n\n[32:16] DM -like axions lower S8\; DE-like axions lower h\n\n[33:54] High-resolution CMB marginally weakens a xion constraint\n\n[40:01] Model galaxy clustering into mildly non-linear regime with EFT of LSS\n\n[42:34] Galaxy cluster ing traces DM clustering - revealing signature of ULAs\n\n[44:05] BOSS DR12 galaxy clustering rule s out new parts of axion parameter space\n\n[45:50] Axions improve consistency between Planck and BOSS\n\n[47:49] BOSS has mild preference at m_a = 10^-26 eV - excluded by Planck\n\n[53:17] Strongest axion bounds come fr om combining CMB & LSS\n\n[54:29] Window of DM-like axions with lower S8\n\n[54:56] Could axions resolve the S8 tension\n\n[55:55] Multi-probe app roach to detect ULAs\n\n[1:00:15] Where to next?\n\n[1:03:35] What current work in cosmology is particularly underapprecia ted by the community?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/62/ END:VEVENT BEGIN:VEVENT SUMMARY:Johannes Lange (Leinweber Center for Theoretical Physics\, Univers ity of Michigan) DTSTART:20230205T050000Z DTEND:20230205T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/63 DESCRIPTION:Title: S8 constraints from (very) non-linear scales in combined DES\, KiD S & BOSS\nby Johannes Lange (Leinweber Center for Theoretical Physics\ , University of Michigan) as part of Cosmology Talks\n\n\nAbstract\nJohann es Lange tells us about his recent work with collaborators constraining co smological parameters\, in particular S8\, using the non-linear scales in the Dark Energy Survey (DES)\, the Kilo Degree Survey (KiDS) and the Baryo n Oscillation Spectroscopic Survey (BOSS).\n\nThey generate predictions fo r the non-linear scales via the Aemulus suite of simulations\, which ran w ith a variety of cosmological parameters. To connect the simulations' halo s with galaxy observations they use a halo occupation distribution (HOD) m odel to generate a large number of sets of mock galaxies. The halo model p arameters are then marginalised over when comparing the mocks to observati ons\, ultimately giving the final cosmology constraints.\n\nAs with more o r less all other large scale structure probes nowadays they find a mild te nsion between their constraints and predictions for S8 coming from CMB obs ervations and the LCDM model.\n\nTalk recording: youtu.be/XxCIpFMP_lw\n\nJohannes' web site: johannesulf.github.io/\n\nPaper: arxiv.org/abs/2301.08692\n\nhalotoo ls code: github.com/astropy /halotools\n\ndsigma code: github.com/johannesulf/dsigma\n\n
\n\nIndex to Key Parts of the Talk\n\n[00:00] Shaun 's intro\n\n[01:16] Johann es' brief opening comments about the paper\n\n[03:45] Two things for people to remember from this t alk\n\n[05:43] What are t he motivations for this work?\n\n[08:26] Several advancements in recent years made this work possib le\n\n[09:12] Halotools\, by Andrew Hearin\n\n[09:26] Multi-Cosmology Simulations\n\n[10:04] "lensing is low"\n\n[13:36] Getting into the details: Galaxy Redshift-Space Clust ering\n\n[15:12] Galaxy-G alaxy Lensing (dsignma python package\, by Johannes)\n\n[17:54] Comparing galaxy-galaxy lensing me asurements in this work vs older measurements\n\n[20:18] Projected Clustering + Lensing\n\n[22 :24] Mock Galaxy Catalogs\n\n[22:41] Multi-Cosmology Simulations -> Aemulus\n\n[24:09] HOD (Halo Occupation Distribution) Model\n\n[25:36] Assembly Bias\n\n[26:22] Velocity and Spatial Bias\n\n[ 28:20] Cosmological Constrai nts\; Cosmology Inference\n\n[32:33] Mock Test\; Figure 2 from paper\n\n[34:48] Blinding\; Figure 5\n\n[35:58] Data fits\; Figure 6\n\n[38:54] S8 Constraints plot\; Figur e 12 (key slide)\n\n[41:47] Where to next? Future Directions\n\n[43:15] SZ Cross-Correlation\n\n[43:50] Baryonic Feedback\n\n[44:58] DESI\, successor to BOSS (expect much better constraints)\n\n[45:42] More tests on mock catalog\n\n[46:23] Speculative question: pretend the S8 tension is syst ematics\, what might be the leading reason for it?\n\n[47:59] What current work in cosmology is pa rticularly underappreciated by the community?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/63/ END:VEVENT BEGIN:VEVENT SUMMARY:Stuart Lyall (Swinburne University) DTSTART:20230302T050000Z DTEND:20230302T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/64 DESCRIPTION:Title: Peculiar velocities will detect or constrain modified gravity (e.g . f(R) & DGP)\nby Stuart Lyall (Swinburne University) as part of Cosmo logy Talks\n\n\nAbstract\nStuart tells us about his recent work exploring how to use peculiar velocity measurements to constrain modified gravity (s pecifically f(R) and DGP models). He finds that even using just linear sca les we would be able to detect or rule out model parameter regions that wo uld be entirely consist with current measurements of the background expans ion.\n\nHe does this by predicting the auto and cross spectra between gala xy overdensity and peculiar velocity\, using just linear theory - and then analysing those observables in modified gravity simulations to measure th e parameters used in the simulations.\n\nAt this point it is just a proof of concept\, as for each modified gravity scenario the method is only cons training the linear galaxy bias and one model parameter (other cosmologica l parameters are known) and also not taking into account additional observ ational uncertainties involved in measuring peculiar velocities in the rea l world.\n\nStill\, the method does work\, at least when the effect produc es a large enough deviation from LCDM so the proof of concept works. Futur e careful work with 6DF and SDSS data (and\, one day soon\, DESI) should a llow the method to bring about real constraints on these models.\n\nRecorded talk\n\nPaper: arxiv.org/abs/2211.07101\n\n
\n\nI ndex to Key Parts of the Talk \n\n[00:00] Introductory comments by Shaun and Stuart\n\n[01:35] < a href="https://youtu.be/7tO1GnB628A?t=95">Two things you would like peopl e to remember from this talk\n\n[02:20] What is Dark Energy?\n\n[03:38] Literature review\n\n[04:15] Peculiar Velocity\n\n[07:15] Growth of Structure\n\n[09:35] Pipeline Overview\n\n[11:43] Modified Gravity Models\n\n[15 :31] Simulation Data\n\n[ 16:05] Correlation Functions< /a>\n\n[17:16] Theoretical C orrelation Functions\n\n[21:52] χ² Fitting\; Figure 3 from paper\n\n[22:38] Results\; Figures 7 and 9\n\n[27:20] Fisher Forecasts\; Figures 11 a nd 12\n\n[29:52] Apply t o Real Surveys\; comments on main purpose of this work\n\n[31:51] Preliminary Real Results\n\n [34:29] Where to next? and I nvestigating Environmental Dependence\n\n[36:48] What current work in cosmology is particularly un derappreciated by the community?\n
\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/64/ END:VEVENT BEGIN:VEVENT SUMMARY:Minh Nguyen (University of Michigan) DTSTART:20230311T050000Z DTEND:20230311T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/65 DESCRIPTION:Title: 3.7 sigma evidence for suppression of growth of structure! (and S_ 8 resolved?)\nby Minh Nguyen (University of Michigan) as part of Cosmo logy Talks\n\n\nAbstract\nMinh Nguyen tells us about his recent work looki ng for evidence of modified gravity in cosmological observations. Rather t han look at a specific model\, Minh and his collaborators look for evidenc e of a deviation in the "growth index" γ.\n\nIn general relativity and Λ CDM γ≃0.55 but in a more general theory of gravity it could deviate. Mi nh looks at measurements of peculiar velocity\, clustering and Planck CMB data (temperature\, polarisation and lensing) and finds 3.7σ evidence for γ greater than 0.55.\n\nThis is not perhaps surprising\, as it ties in w ith the S₈ tension. γ quantifies how fast structure grows in the unive rse and where we already know there is a deficit of structure in the late universe. Moreover γ greater than 0.55 would cause a deficit. \n\nHowever \, it is still impressive that this one parameter is able to provide a goo d fit to the various data sets simultaneously. This doesn't look like a "r esolution" that takes CMB and late universe probes into bad fitting region s of parameter space. In fact\, Planck CMB alone even has weak evidence fo r γ greater than 0.55 because it appears to also help with the A_lens ten sion.\n\nA fascinating development to keep an eye on...\n\nTalk recording\n\nPaper: arxiv.org/abs/2302.01331\n\nMinh: minhmpa.github.io\n\nCode: github.com/MinhMPA/CAMB_GammaPrime _Growth\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/65/ END:VEVENT BEGIN:VEVENT SUMMARY:Giovanni Arico (University of Zurich) DTSTART:20230410T060000Z DTEND:20230410T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/66 DESCRIPTION:Title: Cosmology Without Scale Cuts! (DES Cosmic Shear Baryonified)\n by Giovanni Arico (University of Zurich) as part of Cosmology Talks\n\n\nA bstract\nGiovanni Arico tells us about his recent work adding baryons to t he modelling of Dark Energy Survey cosmic shear analysis. By adding baryon ic modelling he and collaborators are able to use all of the DES data. \n\ nThe cosmological constraints don't tighten a lot\, because although a lot of data is added\, the baryonic effects are largely degenerate with cosmo logy. However\, they are able to obtain a clear lower bound on one of the baryonic parameters\, which parameterises the typical halo mass that has e jected 50% of its gas.\n\nTheir results are 1.4σ different the DES' own c osmic shear analysis\, and therefore their S₈ measurement is not in tens ion with Planck. This isn't mainly due top the baryons though\, so there i s no clear story that "baryons are responsible for the S₈ tension". Inst ead the difference comes roughly half from the methods to include non-line ar clustering and half from intrinsic alignment modelling.\n\nThis isn't a death knell for the S₈ tension in any case because DES cosmic shear alo ne wasn't in very large tension with Planck\, and many other measurements are - however it does highlight how a number of assumptions\, each on thei r own small enough to perhaps not worry about\, can ultimately add up to s omething more substantial.\n\nThe future is bright as\, with appropriate m odelling\, the "baryonification" methods used here can be used for all the other large scale structure measurements out there. Also\, if the baryon parameters are constrained with additional data sets (tSZ\, kSZ\, X-ray te mperature\, stellar mass function\, etc) then the degeneracies with cosmol ogical parameters can be broken\, allowing full constraining power from th ese small scales.\n\nTalk recording \n\nGiovanni: linkedin.com/in/giovanni-aricò-8832684a\n\nPaper: arxiv.org/abs/2303.05537\n\nBACCOemu: bitbucket.org /rangulo/baccoemu/src/master/\n\n
\n\nIndex to Key Parts of the Talk\n\n[00:00] Introducto ry comments by Shaun\n\n[01:38] Giovanni's opening comments on the paper\n\n[02:32] Two things for people to remember from th is talk\n\n[03:58] What m otivated this work?\n\n[05:14] Discussion about the scale cuts\, baryonification process\, etc\ n\n[08:46] Getting into the d etails\n\n[11:11] Model: BACCO framework\n\n[16:16] BACCOemu\n\n[18:57] Pi peline: Bayesian inference (Table I in paper\, free parameters)\n\n[22 :48] Results: Cosmology (Fig ure 3)\n\n[26:21] Result s: Baryons (Figure 4)\n\n[29:53] Results: Intrinsic Alignment\n\n[31:30] Intrinsic alignment of galaxies: NLA preferred ov er TATT\n\n[32:28] S8 te nsion (Figs. 6\, 7)\n\n[36:00] S8 tension (Figure 8)\n\n[40:49] Difference with DES Collaboration (Figure 10)\n\n[49:0 7] Q&A on this work in relat ion to KiDS\n\n[54:16] W here to next?\n\n[56:32] What current work in cosmology is particularly underappreciated by the co mmunity?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/66/ END:VEVENT BEGIN:VEVENT SUMMARY:Jeongin Moon\, David Valcin\, Christoph Saulder (Sejong U\, Ohio U \, Max Planck Inst) DTSTART:20230513T060000Z DTEND:20230513T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/67 DESCRIPTION:Title: Actual DESI Results! - BAO with BOSS Precision after just two mont hs\nby Jeongin Moon\, David Valcin\, Christoph Saulder (Sejong U\, Ohi o U\, Max Planck Inst) as part of Cosmology Talks\n\n\nAbstract\nJeongin M oon\, David Valcin and Christoph Saulder tell us about the first cosmologi cally relevant results from DESI (The Dark Energy Spectroscopic Instrument ). Specifically\, they are presenting the first detection of the BAO (Bary on Acoustic Oscillations) from DESI.\n\nWith a "first detection" one would expect something mediocre\, but even this result\, using only two months of DESI data\, has similar precision to the final BOSS data after years of operation. This is a very exciting time for cosmology as we wait for the full one year DESI results and cosmological constraints.\n\nJeongin\, Davi d and Christoph talk us through the galaxy subsets DESI will use (and whic h they have used in this analysis) as well as the statistical significance of the BAO detection and modelling required to quantify this.\n\nWith thi s detection they are able to also provide a forecast for the one year and five year results that is actually data driven\, based on what they've act ually seen so far (rather than just optimistic modelling). The forecast fo r the five year measurement looks exquisite.\n\nJeongin: arxiv.o rg/search/astro-ph?q...\n\nDavid: inspirehep.net/authors/1887016\n\nChristoph: cosmology.kasi.re.kr /members.php?member=saulder\n\nPaper: 2304.08427\n\n
\n\n[00:00] Intro comments\n\n[01:01] When can we expect the year 1 data analysis?\n\n[01:28] Two things for people to reme mber from this talk\n\n[02:19] What are Baryon Acoustic Oscillations?\n\n[04:16] Why are Baryon Acoustic Oscillations Useful ?\n\n[05:45] BAO Reconstr uction\n\n[09:24] Plan fo r DESI\n\n[10:42] The Ins trument (and comparison with SDSS)\n\n[12:55] Main tracers of DESI\n\n[16:50] DESI will explore a x30 larger map over a x10 larger volume than SDSS\n\n[18:17] Our work with early DESI data\n\n[18:52] First two months of observations\n\n[19:3 4] Correlation function meas urements\n\n[21:40] Simu lations and the covariance matrix\n\n[27:10] Detection in simulations\n\n[30:11] BAO reconstruction efficiency\n\n[31: 20] BAO detection using LRG and BGS\n\n[33:23] Corre lation function measurements\n\n[34:18] Fisher forecast\n\n[35:28] Summary\n\n[37:03] Outlook\n\n[38:21] What current work in cosmology is particularly underappreciated b y the community?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/67/ END:VEVENT BEGIN:VEVENT SUMMARY:Dongwon Han\, Niall MacCrann\, Mathew Madhavacheril\, Frank Qu\, Blake Sherwin (U of Cambridge\, U of Pennsylvania) DTSTART:20230525T060000Z DTEND:20230525T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/68 DESCRIPTION:Title: Advanced ACT Lensing Cosmology (the best high redshift\, large sca le take on the S8 tension)\nby Dongwon Han\, Niall MacCrann\, Mathew Madhavacheril\, Frank Qu\, Blake Sherwin (U of Cambridge\, U of Pennsylvan ia) as part of Cosmology Talks\n\n\nAbstract\nDongwon Han\, Niall MacCran n\, Mathew Madhavacheril\, Frank Qu\, and Blake Sherwin tell us about the Atacama Cosmology Telescope's latest measurement of CMB weak lensing ("Adv anced ACT" to be precise).\n\nIt is quite the measurement. Despite ACT bei ng on the ground\, the measurement now rivals the best Planck lensing meas urement. This means the additional complications of the atmosphere have be en overcome\, and the better technology of telescope possible from not hav ing to put something in space are starting to win.\n\nThe results are fasc inating in the era of S₈ tensions. They match both Planck CMB and Planck lensing (and ACT primary CMB). The CMB lensing measurements are sensitive to larger scales and higher redshifts than other large scale structure pr obes (because the CMB is further away\, so is lensed by stuff further away ). This means that if the S₈ tension is new physics their result seems t o be suggesting it must happen at late times and/or on small scales. Perha ps this is consistent with what other probes are suggesting too?\n\nIn thi s video we hear about the hard work done to eliminate systematic effects a nd make sure noise isn't being mistaken for signal\, and then we hear abou t the cosmology results and their implications for the future.\n\nPaper 1: arxiv.org/abs/2304.05203\nPaper 2: arxiv.org/abs/2304 .05202
\nPaper 3: arxiv. org/abs/2304.05196
\n\nDongwon: dwhan89.github.io
\nNiall: maths.cam.ac.uk/person/nm746
\nMathew: upe nn.edu/people/mathew-madhavacheril
\nFrank: linkedin.com/in/frankqu7
\nBlake: damtp.cam.ac.uk/person/bds30 \n\n[00:00 ] Intro bits
\n[02:50] Why is this important now?
\n[14:32] ACT and its ma ps
\n[18:35] ACT lensing maps
\n[27:56] The power spectrum from the map (and challenges!)
\n[40:54] Cosmology Results! (and implications)
\n[1:01 :39] What comes next (and discussion)
\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/68/ END:VEVENT BEGIN:VEVENT SUMMARY:Alexandra Amon\, Ami Choi\, Anna Porredon\, Catherine Heymans\, Ma rika Asgari\, Simon Samuroff (DES\, KiDS) DTSTART:20230529T060000Z DTEND:20230529T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/69 DESCRIPTION:Title: DES & KiDS Combined Cosmology Constraints (No Tension with Planck? !)\nby Alexandra Amon\, Ami Choi\, Anna Porredon\, Catherine Heymans\, Marika Asgari\, Simon Samuroff (DES\, KiDS) as part of Cosmology Talks\n\ n\nAbstract\nMembers from the Dark Energy Survey and Kilo Degree Survey ha ve teamed up to do a joint cosmic shear analysis\, complete with final cos mology results. They tell us the final cosmology results\, and go into det ails explaining what the technical difficulties were to combine the data s ets.\n\nTalk Recording: youtu.be/T8 hkgJ-hFoo\n\nTalk Slides: https://docs.google.com/ presentation...\n\nPaper: a rxiv.org/abs/2305.17173\n\nAlexandra Amon: alexandraamon.com\n\nAmi Choi: amichoi.github.io\n\nAnna Porredon: ph.ed.ac.uk/...\n\nCatherine Heymans: roe.ac.uk/~heymans\n\nMarika As gari: hull. ac.uk/...\n\nSimon Samuroff: inspirehep.net/...\n\nDES: dark energysurvey.org/...\n\nKiDS: kids.strw.leidenuniv.nl/......\n\nHSC: hsc-release.mtk.nao.ac.jp /...\n\n
\n\n[00:00] Sh aun's intro\n\n[01:13] Op ening comments on the work\; Fig. 7 from the paper\n\n[05:28] The results: KiDS + DES cosmic shear \; Fig. 1\n\n[09:51] Whe n can we expect KiDS + DES 3x2pt analysis?\n\n[11:19] Two takeways for people to remember from thi s talk\n\n[12:06] Backgr ound on the cosmic shear surveys\n\n[13:52] Cosmology from cosmic shear in 2023\n\n[16:20] Overview of the process going f rom input images to output cosmological parameters\n\n[21:15] Analysis choices matter!\n\n[30 :04] Choices made between v arious possible analysis methods\; Mock analysis\; Hybrid pipeline\n\n [36:53] Re-analysis of KiDS -1000 and DES Y3\n\n[42:07] Re-analysis of HSC Y3\n\n[43:52] The combination of the two surveys\n\n[46:27] The S8 tension\n\n[49:40] Analysis variants\n\n[52:14:] Accounting for nonlinear g rowth and baryonic feedback\n\n[56:05] Looking ahead\n\n[59:58] What current work in cosmology is particularly underappre ciated by the community?\n\n[1:00:56] Comments from Catherine Heymans\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/69/ END:VEVENT BEGIN:VEVENT SUMMARY:Jenny Wagner DTSTART:20230625T060000Z DTEND:20230625T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/70 DESCRIPTION:Title: The Case Against the Cosmological Principle (and/or FLRW)\nby Jenny Wagner as part of Cosmology Talks\n\n\nAbstract\nJenny Wagner gives us the observational case for and against the Cosmological Principle\, bas ed on a paper she and 22 co-authors wrote summarising this case. \n\nShe s tarts by clearly defining what the Cosmological Principle is and then talk s us through the observations that she and her coauthors find to be the mo st compelling evidence against the assumptions of full statistical isotrop y and homogeneity. In each case she gives us the story either "side" would need to tell to reconcile the observation (the standard\, FLRW side and t he inhomogeneous cosmology side).\n\nJenny: thegravitygrinch.blogspot.com\n\nRecording: https://youtu.be/nASUsWQyemc\n\nPaper: arXiv: 2207.05765\n\n
\ n\n[00:00] Intr o and take home messages\n\n[07:27] Background and motivation\n\n[12:40] What is the Cosmolo gical Principle?\n\n[20:50] Half sky analyses of the CMB\n\n[30:19] 'Scale of homogeneity' \n\n[38:09] Variations in time and space of cosmological parameters\n\n[51:05] Ellis-Baldw in and anomalous dipoles\n\n[1:01:47] What comes next?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/70/ END:VEVENT BEGIN:VEVENT SUMMARY:Lilan Yang\, Mike Boylan-Kolchin (Kavli IPMU\, U of Texas) DTSTART:20230716T060000Z DTEND:20230716T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/71 DESCRIPTION:Title: Too Big\, Too Early? (High Redshift JWST Galaxies)\nby Lilan Y ang\, Mike Boylan-Kolchin (Kavli IPMU\, U of Texas) as part of Cosmology T alks\n\n\nAbstract\nLilan Yang and Mike Boylan-Kolchin tell us about high redshift JWST galaxies. Lilan is one of the astronomers using JWST to look at high redshifts and find new galaxies. Mike is a cosmologist who has pi oneered looking at these high redshift galaxies to think about cosmology.\ n\nRecording: https://youtu.be/ApB4 Jv3P9Gs\n\nPapers: 2207.131 01\, 2207.13527\, 2208.01611\, 2212.06666\n\n00:00 Shaun's Intro\n\n01:19 Lilan intro to JWST\n\n0 5:40 Lilan: W hat are the first stars and galaxies?\n\n13:02 Lilan: How did reionization occur?\n\n28:03 Mike: Are observed structures consistent with initial conditions?\n\n4 7:01 Mike: P hysics beyond ΛCDM\n\n1:00:03 Lilan and Mike: Summary and what's next?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/71/ END:VEVENT BEGIN:VEVENT SUMMARY:Cyril Creque-Sarbinowski (Center for Computational Astrophysics\, Flatiron Institute) DTSTART:20230827T060000Z DTEND:20230827T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/72 DESCRIPTION:Title: Parity Violation from Inflation (via Chern-Simons Gravity)\nby Cyril Creque-Sarbinowski (Center for Computational Astrophysics\, Flatiro n Institute) as part of Cosmology Talks\n\n\nAbstract\nCyril Creque-Sarbin owski tells us about recent work on Chern-Simons gravity and how if it is the correct general model of gravity then parity violation can be generate d during inflation in such a way that correlation functions of galaxies me asured today could see that parity violation. Given the recent evidence fo r parity violation in galaxy correlation functions\, that is intriguing.\n \nThe model also requires parameter values that could produce baryogenesis \, so the same physics would end up producing the (observed?) parity viola tion and the baryon asymmetry in the universe.\n\nEven if the current hint s of parity violation turn out to be wrong\, future experiments would be s ensitive to smaller magnitudes of this effect\, meaning the model will be well constrained by the next wave of large scale structure measurements\n\ nCyril: cyril-creque.github.io\n\nPaper: arxiv.org/abs/2303 .04815\n\n
\n\n[00:00] S ean's intro\n\n[00:47] Cyr il's brief intro on the paper\n\n[01:46] Two things to remember from this talk\n\n[02:17] The motivation for this work\n \n[03:15] What is Parity? How can Gravity violate it?\n\n[05:25] What is [dynamical] Chern-Simons (dCS) Gravity?\n\n[07:33] How can Parity be Observed? ( Galaxy N-Point Functions)\n\n[09:02] The Galaxy Four Point Function / Trispectrum\n\n[11:53] Inflation: A Lightning Review\n\n[14:43] dCS Inflation: Full Action\n\n[18:58] P rimordial Scalar Trispectrum from dCS\n\n[23:55] The Collapsed Limit\n\n[24:24] The Collapsed Limit Scalar Trispectra\ n\n[31:21] Two Examples Beyo nd Vanilla dCS Inflation\n\n[35:37] How Sensitive are we to Collapsed Trispectra?\n\n[44:05] < a href="https://youtu.be/IxhbpfblhQQ?t=2645">What about Experiments?\n \n[46:17] dCS Inflation: Lep to/Baryogenesis\n\n[53:35] Conclusions / Future Extensions\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/72/ END:VEVENT BEGIN:VEVENT SUMMARY:Gerrit Farren\, Alex Krolewski (Cambridge\, Perimeter Institute) DTSTART:20230911T060000Z DTEND:20230911T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/73 DESCRIPTION:Title: S8 at low redshift and large scales - ACT lensing X unWISE galaxie s\nby Gerrit Farren\, Alex Krolewski (Cambridge\, Perimeter Institute) as part of Cosmology Talks\n\n\nAbstract\nGerrit Farren and Alex Krolewsk i tell us about their work cross correlating the ACT lensing maps with unW ISE galaxies. Their method is an update of earlier analyses using Planck l ensing. Those earlier analyses were in tension with Planck primary CMB mea surements\, which was similar to e.g. cosmic shear\, and other clustering measurements\, at smaller scales.\n\nCuriously\, this new analysis reveals no tension with primary CMB. A re-analysis of Planck lensing cross unWISE \, with updated assumptions and modelling\, shows that Planck lensing is a ctually also not in tension with primary CMB (a combination of effects wer e responsible for removing the tension).\n\nThis analysis covers the large (ish) scale low(ish) redshift quadrant of the (k\,z) space\, suggesting th at the origin of the S8 tension is likely to either be a very low redshift phenomenon\, or scale dependent.\n\nHowever Alex and Gerrit do note that a recent cross-correlation of Planck with DESI LRGs does seem to still ind icate some tension at the same redshift and scales\, so the dust hasn't 10 0% settled on the large scale\, low redshift quadrant.\n\nVideo recording: youtu.be/Y_QMPWDi95s\n\nGerrit : maths.cam.ac.uk/perso n/gsf29\n\nAlex: perimeterinstitute.ca/people/alex-krolewski\n\nPaper: arXiv: 2309.05659\n\n
\n[00:00] Shaun's intro\n\n[01:06] Overview comments by Gerrit an d Alex\n\n[03:31] Two thi ngs to remember from this talk\n\n[04:40] Motivations for this work\n\n[07:41] Measuring S8 with galaxy-CMB lensing cross-co rrelations\n\n[09:16] New ACT DR6 X unWISE spectra (Fig. 3 from paper)\n\n[12:03] Q&A: Advantages of using UnWISE vs eBOSS i n this work\n\n[13:13] Ba ckground: defining the unWISE sample\n\n[18:21] Background: previous unWISE-Planck results\n\n [19:08] Clustering redshifts for unWISE\n\n[21:00] I mproving the galaxy sample: updated redshift distribution\n\n[22:24] < a href="https://youtu.be/Y_QMPWDi95s?t=1344">Mitigating systematic density fluctuations\n\n[25:59] Modelling improvements: Redshift marginalisation (Fig. 17)\n\n[27:45] Modelling improvements: The power spectrum model\n\n[29:36] Series of systematics tests: Data null-tests\n\n[31:06] Series of systematics tests: Simu lation driven tests (Fig. 12)\n\n[31:58] Series of systematics tests: Parameter consistency tests (Fig. 21)\n\n[32:28] Cos mology from ACT DR6 Lensing X unWISE (Fig. 19)\n\n[35:33] Reanalysing Planck Lensing X unWISE: MC norm correction\n\n[36:47] Reanalysing Planck Lensing X unWISE: Planck PR4 lensing\n\n[37:16] Reanalysing Planck Lensing X unWISE: summary of changes\n\n[38:12] Reanalysing Planck Lensing X unWISE: Cosmology\n\n[40:2 2] Joint constraints from AC T DR6 and Planck PR4 X unWISE (Fig. 23)\n\n[41:12] Comparing to other analyses (Fig. 23)\n\n[4 5:09] Future CMB lensing cro ss-correlations\n\n[50:51] What current work in cosmology is particularly underappreciated by the community?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/73/ END:VEVENT BEGIN:VEVENT SUMMARY:Melissa Diamond\, Chris Cappiello (Queens U.) DTSTART:20231003T050000Z DTEND:20231003T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/74 DESCRIPTION:Title: If Dark Matter Interacts with Protons We Could See It Scatter Elec trons\nby Melissa Diamond\, Chris Cappiello (Queens U.) as part of Cos mology Talks\n\n\nAbstract\nMelissa Diamond\, joined by Chris Cappiello\, tells us how dark matter interactions with one set of standard model parti cles might be first constrained via experiments looking for interactions w ith other particles.\n\nAs a first example they explore how loop diagrams that arise when dark matter interacts with quarks (and thus pions\, neutro ns and protons)\, necessarily introduce an interaction with electrons too. For light enough dark matter\, this would mean that the first direct dete ction of these dark matter models would come via electron scattering exper iments\, not nucleon scattering experiments.\n\nAt the moment this just ad ds to constraints in somewhat less-interesting parameter space\, but futur e experiments will push the constraints into well motivated parameter rang es for dark matter production mechanisms.\n\nThis loop interaction would a lso generate a dark matter "millicharge"\, which could be combined with as trophysical observations to make even tighter constraints.\n\nTalk recordi ng: youtu.be/gixAFpnVhAw\n\nPap er: arXiv: 2307.13727\n\nMe lissa: inspirehep.net/aut hors/1945406\n\nChris: mcdonaldinstitute.ca/chris-cappiello\n\n
\n\nIndex to Key Parts of the Talk\n\n[00:00] Shaun's intro\n\n[00:56] Overview comments by Melissa\n\n[01:39] Two things to remember from this talk\n\n [02:31] Motivations for this work\n\n[04:48] Explanati on of Figure 1 from paper\n\n[06:20] Why should there be an interaction of DM with the SM?\n\n[ 08:04] More specific motivati on\n\n[09:35] Chris on SE NSEI and DAMIC\n\n[12:24] Explanation of the blue Cosmology line on the plot\n\n[13:20] Getting into the details (Figs. 2\, 7)\n\n[20:41] Chiral Eff ective Interaction\n\n[26:44] Calculating the Cross Sections\n\n[30:50] Effective Electron Cross Section\n\n[32:25] Probe Hadrophilic DM with a He avy Mediator using Electron Coil Detectors\n\n[35:15] Bounds from Effective Millicharge\n\n[44 :48] Where to next?\n\n[ 52:12] What current work in cosmology is particularly underappreciated by the community?\n\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/74/ END:VEVENT BEGIN:VEVENT SUMMARY:Kate Clements (University of Nottingham) DTSTART:20231103T050000Z DTEND:20231103T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/75 DESCRIPTION:Title: A Lab Experiment to Detect Dark Sector Domain Wall\nby Kate Cl ements (University of Nottingham) as part of Cosmology Talks\n\n\nAbstract \nKate tells us about her recent work showing how domain walls in the dark sector could be trapped in a laboratory. \n\nIn many well motivated model s\, a scalar field in the dark sector can have a double well potential. In this case\, the scalar field can form "domain walls" if in some region of space the field occupies one side of the well\, and in other regions of s pace the field occupies the other side of the well. The wall occurs at the transition point between the two regions.\n\nNormally such domain walls w ill not stick around\, either evaporating\, or simply moving away from an observer. However\, by putting a density spike in a vacuum chamber one can trap a domain wall in place. Once trapped\, one could observe the domain wall's effects on standard model particles\, e.g. cold atoms\, via a chang e in a fifth force.\n\nOf all the ways we're looking for new fundamental p hysics\, this sort of experiment would be the coolest if it worked\, as it would be reproducible in labs around the world\, making experimental fund amental physics cheap (ish) again.\n\nPaper: arXiv:2308.01179\n\nTalk Video: youtu.be/U6arawZnxHQ\n\nKate: linkedin.com: Kate Clements\n\n\n\nIndex to Key Parts of the Talk
\n[00:00] Shaun's intro\n\n[00:39] Overview comments by Kate\n\n[01: 21] Two things to remember fr om this talk\n\n[02:07] Motivations for this work (Fig. 1 from the paper)\n\n[04:42] Detecting Dark Domain Walls\n\n[0 5:57] What is a Domain Wall? \n\n[08:45] Infinite Dom ain Walls\n\n[09:37] Vac uum Chamber Experiment\n\n[12:49] Thin Domain Walls (Fig. 2)\n\n[14:41] Thick Domain Walls (Fig. 3)\n\n[16:00] What Next?\n\n[24:48] What current work in cosmology is pa rticularly underappreciated by the community?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/75/ END:VEVENT BEGIN:VEVENT SUMMARY:Keir Rogers\, Vivian Poulin (U Toronto\, U Montpellier) DTSTART:20231201T050000Z DTEND:20231201T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/76 DESCRIPTION:Title: 4.9σ evidence for axions & warm dark matter - eBOSS Lyα vs Planc k CMB\nby Keir Rogers\, Vivian Poulin (U Toronto\, U Montpellier) as p art of Cosmology Talks\n\n\nAbstract\nKeir and Vivian tell us about their recent work looking at the Lyman-α power spectrum from eBOSS quasars. Spe cifically\, they look at how consistent this power spectrum is with the po wer spectrum one would expect from the relevant scales given Planck CMB ob servations within the ΛCDM model and find a whopping 4.9σ tension.\n\nTh ere have been hints of a tension between Lyman-α and CMB for a while\, bu t not with this magnitude. Keir and Vivian focus their analysis on the sca les and observables that the eBOSS Lyman-α are most sensitive to and see that the slope of the power spectrum of this range of scales is very diffe rent to what is seen on CMB scales. Within ΛCDM the slope of the power sp ectrum should be constant\, hence the whopping tension.\n\nMost excitingly \, they also find three simple models that more or less completely solve t he tension\, without harming any other observations! These are a one-param eter power-law running of the "spectral index" (i.e. the slope of the powe r spectrum)\, and a small fraction of axion "ultralight" dark matter\, or warm dark matter. For the axion and warm dark matter models there are two free parameters (the mass and the fraction of the total dark matter). The running and axion models in particular completely remove the tension\, and the warm dark matter reduces the "tension" to 1.5σ. Very exciting!\n\nVi deo Recording: youtu.be/_cueUDEf6n4 \n\nKeir: keirkwame.github.io/< /a>\n\nVivian: inspire.ne t/authors/1341720\n\nPaper: arXiv: 2311.16377\n\n
\n\nIndex to Key Parts of the Talk\n[00:00] Shaun's intro \n\n[01:04] Overview comm ents by Keir and Viv\n\n[03:25] Two things to remember from this talk\n\n[06:45] Motivations for this work\n\n[11:35] Getting into the Details \n\n[15:57] All the cosmolog ical info in the eBOSS Lyα forest compressed to two parameters\n\n[17 :20] This compression is va lid for all the models we consider (Fig. 4 from paper)\n\n[18:26] 4.9σ tension between eBOSS Ly- αf & Planck CMB (Fig. 1)\n\n[20:11] Clarifying comments by Shaun (editing insert)\n\n[23:27] CMB+BAO+SNe vs Lyα\; powe r spectrum running\, ULA\, WDM (Fig. 2 top)\n\n[34:40] Tension missed when looking at omega_8\, n _s (Fig. 2 bottom\n\n[36:35] Planck CMB+BAO+SNe+eBOSS Ly-αf constraints on primordial power spec trum (Fig. 3)\n\n[37:39] Planck CMB+BAO+SNe+eBOSS Ly-αf constraints on nature of dark matter (Fi g. 3)\n\n[39:25] What e lse may be causing this discrepancy?\n\n[41:35] Where to next?\n\n[51:29] Vivian's supplemental comment on neutrino mass constraints\n\n[52:38] Keir - follow-up coming from DESI\n\n[52:59] What current work in cosmology is particularly unde rappreciated by the community?\n\n[55:23] Final question to Keir about how these findings relate to work discussed in an earlier Cosmology Talk\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/76/ END:VEVENT BEGIN:VEVENT SUMMARY:Lamman\, Legnani\, Shi\, Sarcevic\, Pyne\, and Ferreira DTSTART:20240221T050000Z DTEND:20240221T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/77 DESCRIPTION:Title: Intrinsic Alignments: A Guide for Everyone\nby Lamman\, Legnan i\, Shi\, Sarcevic\, Pyne\, and Ferreira as part of Cosmology Talks\n\n\nA bstract\nClaire Lamman\, Jingjing Shi\, Niko Šarčević\, Susan Pyne\, El isa Legnani and Tassia Ferreira tell us about the intrinsic alignments gui de they wrote (along with Eleni Tsaprazi\, who couldn’t make the video r ecording).\n\nThey wanted to write something that wasn’t quite a review\ , but also wasn’t quite a set of lecture notes. Instead they aimed for w hat might be best framed as a “cheat sheet” for intrinsic alignments. Everything you need to know about the topic\, compressed into one article. However\, there’s still a lot about the topic\, so the compression is s till 33 pages and 10 figures big.\n\nTo construct the guide they broke the topic of intrinsic alignments into sub-fields and then asked questions li ke “what are the key equations for this sub-field?”\, “what are the different notations people use?”\, “what might be confusing to a newco mer?” They then wrote the guide to answer those questions\, even includi ng subsections with quick definitions of each common term\, and short list s of common alternative notations.\n\nIn this video they go over both the guide and the topic of intrinsic alignments.\n\nVideo: youtu.be/BlibRW4XpR8\n\nPaper: arXiv:2309.08605 \n\n\nClaire: cmlamman.github.io/\n\nJingjing: jshiastro.com\n\nNiko: nikosarcevic.com\n\nSusan: www.ucl.ac.uk/astrop hysics/susan-pyne-honorary-research-fellow\n\nElisa: elisalegnani.github.io\n\nTassia: physics.ox.ac.uk/our-peop le/ferreirat\n\nEleni: https://tsaprazi .eu\n\n\n
\n\nIndex to Key Parts of the Talk\n\n[0:00:00] Shaun's intro\n\n[0:01:13] < a href="https://youtu.be/BlibRW4XpR8?t=73s">What are intrinsic alignments? plus IA cheat sheet\n\n[0:02:54] Two things to remember from this talk\n\n[0:03:17] Getting into the background and detai ls\n\n[0:10:04] Elliptic ity (section 2 of paper*)\n\n[0:12:38] Galaxy types and shapes\n\n[0:16:31] IA Correlation Function Notation (section 4*)< /a>\n\n[0:19:02] IA Correla tion Functions (section 5*)\n\n[0:23:01] Correlations\n\n[0:23:34] Shear (section 3*)\n\n[0:30:54] 3D IA Power Spectrum (section 6*)\n\n[0: 38:33] 2D IA Power Spectrum (section 7*)\n\n[0:46:01] Modeling (section 8*)\n\n[1:00:41] Where to next?\n\n[1:06:44] What current work in cosmology is particularly underap preciated by the community?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/77/ END:VEVENT BEGIN:VEVENT SUMMARY:Pritha Paul\, Chris Clarkson (QMUL) DTSTART:20240308T050000Z DTEND:20240308T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/78 DESCRIPTION:Title: There is Parity Violation in Standard Observational Cosmology\ nby Pritha Paul\, Chris Clarkson (QMUL) as part of Cosmology Talks\n\n\nAb stract\nThere is Parity Violation in Standard Observational Cosmology (Pri tha Paul and Chris Clarkson)\n\nPritha Paul and Chris Clarkson tell us abo ut their work\, along with Roy Maartens\, delving very deeply into standar d observational cosmology. Specifically\, they have looked at relativistic effects in the four point function/trispectrum of galaxy positions.\n\nTh is might sound crazy and masochistic\, but there are big rewards. On large enough scales\, the relativistic effects start to grow\, and tantalisingl y\, once one takes into account both relativistic effects and the observat ional effects of observing in redshift space\, a parity violating signal e merges in both the bispectrum and trispectrum on large scales. This is ver y interesting given the possible observations of parity violation in the f our point function of galaxy positions (i.e. Fourier transform of the tris pectrum).\n\nThere are reasons to suspect the effect Pritha\, Chris and Ro y have uncovered within standard cosmology couldn't be the thing potential ly observed in the four point function\, however it is possible to at leas t tell a story about how the one effect might show up in the other observa tion. Time will tell whether they are indeed related.\n\nIrrespective of t hat\, the result is still interesting as it is likely that Euclid and/or S KA will be able to spot this signal\, thus detecting the effects of relati vity within the large scale structure.\n\nTalk recording on the Cosmology Talks youtube channel\n\nPritha's QMUL profile page\n\nChris' QMUL profile page\n \nPaper: arXiv: 2402.16478\ n\n
\n\nIndex to Key Parts of the Talk\n\n[00:00] Shaun's intro\n\n[01:26] Overview by Pritha and Chris and 2 takeaways from the talk\n\n[02:34] What is the motivation for this work?\n\n[05:03] Why the 4-pt correlation function is needed \n\n[05:58] Recent work by o thers\n\n[09:37] Large S cale Surveys\n\n[11:35] Real Space to Redshift Space - Power Spectrum\n\n[15:36] Real Space to Redshift Space - Bipectrum< /a>\n\n[19:38] Tree Level T rispectrum\n\n[20:59] T rispectrum Geometry\n\n[21:43] Third order number counts\n\n[26:30] Trispectrum\n\n[26:55] Calculating the Trispectrum\n\n[30:50] 15-min Q & A segment\n\n[46:10] What current work in cosmol ogy is particularly underappreciated by the community?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/78/ END:VEVENT BEGIN:VEVENT SUMMARY:Sylvia Wenmachers (Institute of Philosophy\, KU Leuven) DTSTART:20240316T050000Z DTEND:20240316T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/79 DESCRIPTION:Title: New Probability Axioms Could Fix Cosmology's Multiverse (Partially )\nby Sylvia Wenmachers (Institute of Philosophy\, KU Leuven) as part of Cosmology Talks\n\n\nAbstract\nSylvia is a philosopher of science. Her focus is probability and she has worked on a few theories that aim to exte nd and modify the standard axioms of probability in order to tackle parado xes related to infinite spaces. In particular there is a paradox of the "i nfinite fair lottery" where within standard probability it seems impossibl e to write down a "fair" probability function on the integers. If you give the integers any non-zero probability\, the total probability of all inte gers is unbounded\, so the function is not normalisable. If you give the i ntegers zero probability\, the total probability of all integers is also z ero. No other option seems viable for a fair distribution.\n\nThis paradox arises in a number of places within cosmology\, especially in the context of eternal inflation and a possible multiverse of big bangs bubbling off. If every bubble is to be treated fairly\, and there will ultimately be an unbounded number of them\, how do we assign probability?\n\nThe proposed solutions involve hyper-real numbers\, such as infinitesimals and infiniti es with different relative sizes\, (reflecting how quickly things converge or diverge respectively).\n\nThe multiverse has other problems\, and othe r areas of cosmology where this issue arises also have their own problems (e.g. the initial conditions of inflation)\; however this could very well be part of the way towards fixing the cosmological multiverse.\n\nTalk rec ording: youtu.be/MBeSoig4DPY\n\ nSylvia: sylviawenmackers.be\n\nPaper: arXiv: 2308.12229\n\n
\n\n[0:00:00] Shaun' s intro\n\n[0:02:17] Syl via's overview\n\n[0:03:49] Two takeaways from this talk\n\n[0:06:36] The motivation and reason for timing of this work\n\n[0:09:54] Two probabili stic questions\n\n[0:10:22] 1. Probability of inflation\n\n[0:11:03] 2. Predictability problem\n\n[0:14:27] Infinite phase space\n\n[0:16:01] Probability formalisms\n \n[0:19:20] Paradox: fair i nfinite lottery\n\n[0:20:56] Standard probability theory\n\n[0:23:07] Paradox: fair lottery on N\n\n[0:26:40] Finitely additive probability \n\n[0:33:00] Non-Archimede an probability\n\n[0:41:10] Non-normal quasi-probability\n\n[0:45:27] Infinite lottery logic (ILL)\n\n[0:47:53] Implications for inflation theo ry?\n\n[1:02:05] Where to next?\n\n[1:08:27] W hat current work in cosmology is particularly underappreciated by the comm unity?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/79/ END:VEVENT BEGIN:VEVENT SUMMARY:Andreu Font-Ribera\, Seshadri Nadathur (IFAE\, U of Portsmouth) DTSTART:20240404T050000Z DTEND:20240404T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/80 DESCRIPTION:Title: DESI 2024 - Cosmological Constraints from BAO (Font-Ribera and Nad athur)\nby Andreu Font-Ribera\, Seshadri Nadathur (IFAE\, U of Portsmo uth) as part of Cosmology Talks\n\n\nAbstract\nThe Dark Energy Spectroscop ic Instrument (DESI) has produced cosmological constraints! And it is livi ng up to its name.\n\nTwo researchers from DESI\, Seshadri Nadathur and An dreu Font-Ribera\, tell us about DESI's measurements of the Baryon Acousti c Oscillations (BAO) released today. These results use one full year of DE SI data and are the first cosmological constraints from the telescope that have been released.\n\nMostly\, it is what you might expect: tighter cons traints. However\, in the realm of the equation of state of dark energy\, they find\, even with BAO alone\, that there is a hint of evidence for evo lving dark energy. When they combine their data with CMB and Supernovae\, who both also find small hints of evolving dark energy on their own\, the evidence for dark energy not being a cosmological constant jumps as high a s 3.9σ with one combination of the datasets.\n\nIt seems there still is " concordance cosmology"\, it's just not ΛCDM for these datasets.\n\nThe fa ct that all three probes are tentatively favouring this is intriguing\, as it makes it unlikely to be due to systematic errors in one measurement pi peline.\n\nWatch this space for updates!\n\nVideo recording: youtu.be/9DsMphPfrjI\n\nThe papers: data.desi.lbl.gov/doc/papers/\ n\narXiv: 2404.03000\, 2404.03001\, 2404.03002\n\nDESI: desi.lbl.gov/\n\nAndreu: andreufont.github.io/\n\nSesh: seshnadathur.github.io/\n\n
\n\nIndex to Key Parts of the Talk\n\n[0:00:00] Shau n's intro\n\n[0:00:36] Op ening overview and quick peak of results by Andreu and Sesh\n\n[0:01:3 7] BAO results from DESI DR1< /a>\n\n[0:02:14] DESI BAO an d Dark Energy\n\n[0:04:54] DESI BAO and neutrino masses\n\n[0:05:18] DESI BAO and the Hubble Tension\n\n[0:06:31] Main talk: background\, details\ , results (starting with BAO)\n\n[0:09:43] DESI: the instrument\n\n[0:11:05] DESI: the survey\n\n[0:12:04] DESI Data Release 1 (DR1)\n\n[0:18: 11] BAO measurements with g alaxies & quasars at z<2\n\n[0:21:32] Non-linear evolution and Density field reconstruction\n \n[0:23:41] How is the DESI BAO analysis different?\n\n[0:30:08] Tests of systematic errors\n\n[0:34:02] Unblinded data results!\n\n[0:39:16] < a href="https://youtu.be/9DsMphPfrjI?t=2356s">BAO measurements from the Ly man-α forest at z>2\n\n[0:45:16] Lyα BAO: Analysis Validation\n\n[0:48:41] Lyα BAO: Unblinding!\n\n[0:51:10] DESI DR1 Lyα BAO: Publications \n\n[0:53:42] Cosmologi cal Constraints: Flat ΛCDM from DESI BAO\n\n[0:58:02] Breaking the H_0-r_d degeneracy\n\n[1: 01:35] DESI BAO and the Hub ble Tension\n\n[1:03:54] DESI BAO and neutrino masses\n\n[1:10:52] DESI BAO and Dark Energy\n\n[1:23:06] Summary\n\n[1:24:00] What's next?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/80/ END:VEVENT BEGIN:VEVENT SUMMARY:Russell Boey\, Richard Easther\, Yourong Frank Wang (University of Auckland) DTSTART:20240411T060000Z DTEND:20240411T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/81 DESCRIPTION:Title: Black Holes in Ultralight Dark Matter - Slowed Down and Sped Up?\nby Russell Boey\, Richard Easther\, Yourong Frank Wang (University of Auckland) as part of Cosmology Talks\n\n\nAbstract\nRussell Boey\, along w ith his coauthors Richard Easther and Yourong Wang\, tells us about his si mulations of a supermassive blackhole travelling through an ultralight dar k matter soliton. In particular\, he has studied the dynamical friction ef fect on the blackhole within the soliton. \n\nThis is especially interesti ng in the context of the "final parsec" problem\, where the orbits of supe rmassive blackhole binary systems stall in their decay as they reach one p arsec separation. Maybe a different background\, in the form of ULDM inste ad of WIMP DM\, could help?\n\nAn ultralight dark matter soliton is much m ore dense than expectations from "ordinary" WIMP-like dark matter\, so it is also expected that the dynamical friction in such a soliton should be l arge. This is indeed what Russell\, Richard and Yourong found (and other c oauthor Emily Kendall who isn't present in the video). However\, curiously \, they also found a secondary effect where the blackhole perturbs the sol iton\, which in turn causes the soliton to backreact on the blackhole and sometimes speed it back up.\n\nThere is definitely interesting physics to explore inside galaxies in ultralight dark matter systems\, but no verdict just yet on whether the final parsec has been overcome or not.\n\nTalk re cording: https://www.youtube.com/watch?v=hyf6VtbZ6-c\n\nRussell: https://p rofiles.auckland.ac.nz/russell-boey\n\nRichard: https://profiles.auckland. ac.nz/r-easther/about\n\nYourong: https://fwphys.com/\n\nThe paper: https: //arxiv.org/abs/2403.09038\n\nThe earlier paper: https://arxiv.org/abs/211 0.03428\n\n
\n\nIndex to Key Parts of the Talk\n\n[00:00] Shaun's intro\n\n[01:14] Opening remarks by Russell\n\n[0 2:02] Two things to remember about this talk\n\n[04:08] Motivation for this work (The Final Parsec Problem)\n\n[06:49] Ultralight Dark Matter\n\n[ 09:07] Objective\n\n[12: 10] Explaining use of the Sc hrodinger-Poisson equations\n\n[13:44] Getting into the details - Setup\n\n[17:14] Dynamical Friction Theory\n\n[22:2 4] Semi-Analytic Model\ n\n[25:28] Simulation Behav ior\n\n[30:01] Numerica l Dependencies\n\n[33:19] Black Hole Mass Dependence\n\n[34:46] ULDM Mass Dependence\n\n[36:38] Soliton Mass Dependence\n\n[38:22] Semi Analytic Model Comparison\ n\n[40:51] Overdensities\n\n[43:12] Force Comparis on\n\n[45:40] Conclusio n\n\n[51:48] What next? \n\n[56:34] What curren t work in cosmology is interesting but underappreciated by the community?< /a>\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/81/ END:VEVENT BEGIN:VEVENT SUMMARY:Minh Nguyen\, Beatriz Tucci (University of Michigan\, Max-Planck-I nstitut für Astrophysik) DTSTART:20240503T060000Z DTEND:20240503T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/82 DESCRIPTION:Title: Field Level Inference - Up to 5 sigma Better than Power and Bispec trum!\nby Minh Nguyen\, Beatriz Tucci (University of Michigan\, Max-Pl anck-Institut für Astrophysik) as part of Cosmology Talks\n\n\nAbstract\n Nhat-Minh Nguyen and Beatrice Tucci tell us about their recent work compar ing the performance of field inference (FLI) and simulation based inferenc e (SBI). In an apples to apples comparison\, they find that FLI comfortabl y outperforms SBI\, even in what is essentially the "best case scenario" f or SBI.\n\nField level inference gives up on using "summary statistics" to construct a cosmological likelihood (e.g. the power spectrum\, the bispec trum\, the location of the BAO peak\, voids\, etc) and instead constructs the cosmological likelihood at the level of the field itself. In other wor ds the likelihood step of a statistical analysis is done comparing the mea sured density field at each point in Fourier space to a model's actual den sity field. This means the set of model "parameters" necessarily also incl udes the entire set of Fourier modes of the initial conditions. Then\, for example\, when one would then talk about the "maximum likelihood" paramet ers in a FLI inference\, one is talking also about the maximum likelihood set of initial conditions.\n\nOne then does the rest of the statistical an alysis more or less the same as if one is analysing a measured power spect rum\, e.g. one has priors on the inferred parameters\, one has the likelih ood function\, and one produces posterior probability distributions for al l of the model parameters.\n\nIn this analysis they fixed all cosmological parameters except the overall amplitude of the initial density fluctuatio ns\, via σ8. This means they also restricted the set of initial density f luctuations to those with a certain spectral index\, but varied over all s ets of initial density fluctuations that do produce this spectral index. T hey then evolve the initial conditions forward in time using the LEFTfield framework and do the FLI analysis on the evolved field.\n\nSBI however still uses summary statistics\, in this case the power spectrum a nd bispectrum\, but uses simulations to construct the likelihood\, rather than making model based assumptions for what these statistics should look like.\n\nIn this analysis they are only comparing the performance of FLI a nd SBI at reconstructing the parameters of simulations\, because the obser ved data in e.g. BOSS or DESI is only well-calibrated at the level of the power spectrum (and maybe the bispectrum?)\, but not the full non-linear d ensity field that FLI can probe - and where its true improvements lie.\n\n However\, they find FLI outperforms SBI with error bars substantially smal ler (by factors of 2-5 depending on the scales and simulations considered) . This shows that if we could perform field level inference on current or future data sets\, the level of constraints we could obtain would also be substantially improved (e.g\, maybe even a 1σ deviation would become a 5 σ detection!?)\n\nRecorded Talk Video: youtu.be/Pxfsf89jZwI\n\nMinh: minhmpa.github.io/\n\nBeatriz: wwwmpa.mpa-garching.mpg.de/~tucci/\n\nP aper: arXiv:2403.03220\n\n< hr>\n\nIndex to Key Parts of the Talk\n\n[00:00] Shaun's intro\n\n[01:20] Opening remarks by Minh and Beatriz\n\n[02:3 9] Takeaways to remember abo ut this talk\n\n[05:48] Motivation for this work\n\n[08:45] Getting into the details: Amplitude of Structure Growth\n\ n[09:52] Galaxy clustering c an distinguish scenarios of new physics\n\n[10:49] Galaxy bias - response of galaxy formation to f luctuations\n\n[11:47] G alaxy bias spoils constraint from galaxy clustering\n\n[12:30] Effective Field Theory of galaxy bi as\n\n[15:45] FBI (field -level Bayesian inference) and SBI (simulation-based inference) posteriors \n\n[18:46] Extended di scussion at the Field-Level Inference slide\n\n[29:17] Apple-to-apple comparison of FBI and SBI P +B\n\n[31:12] Simulatio n-based inference\n\n[33:06] Neural Posterior Estimation (NPE)\n\n[34:35] Normalizing flows\n\n[35:37] SBI wrap-up putting it all together\ n\n[40:37] Improvement incr eases with scale cuts\n\n[43:02] Robust improvement across samples\n\n[44:50] Where to next?\n\n[49:30] What current work in cosmology is inter esting but underappreciated by the community?\n\n[50:24] Beyond 2-point mock data challenge\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/82/ END:VEVENT BEGIN:VEVENT SUMMARY:Mark Fromhold\, Lucia Hackermuller (University of Nottingham) DTSTART:20240523T060000Z DTEND:20240523T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/83 DESCRIPTION:Title: Fundamental Cosmology from the Lab\nby Mark Fromhold\, Lucia H ackermuller (University of Nottingham) as part of Cosmology Talks\n\n\nAbs tract\nMark Fromhold and Lucia Hackermuller tell us about how they are 3D printing atom traps that allow them to cool atoms to a few micro Kelvin. T his is super interesting for cosmology because it would allow them\, among many other things\, to potentially trap dark domain walls. We learned in another recent cosmology talk about the physics behind these dark domain w alls\, now here is the physics behind the cold atom trap.\n\nIn principle these traps may one day measure the gravitational effects of quantum objec ts\, ultimately testing whether space-time curvature can be in a quantum s uperposition or not.\n\nTalk video: https://youtu.be/1XAbMkoQeXg\n\nLucia: https://www.nottingham.ac.uk/physics/people/lucia.hackermuller\n\nMark: h ttps://www.nottingham.ac.uk/physics/people/mark.fromhold\n\nDark Domain Wa lls: https://arxiv.org/abs/2308.01179\n\n
\nIndex to Key Parts of th e Talk\n\n[00:00] Shaun's intro\n\n[01:04] Opening remarks by Lucia and Mark\n\n[04:47] Timing & enabling investments in Quantum 2.0 technologies \n\n[09:18] How are atoms co oled to <1 millionth degree above absolute zero?\n\n[15:50] Ultracold atoms\, setup in the lab\, l aser system\n\n[20:12] Movie - Lithium MOT\n\n[21:05] Evaporative cooling - Lithium\n\n[26:02] Li_2 Bose-Einstein Condensate\n\n[27:47] Quantum 2.0 sensors\n\n[32 :15] 3D printed chambers\n\n[34:23] Printed surfac es\n\n[35:17] Parts for Quantum 2.0 technologies\; New manufacturing techniques\n\n[37:53] New hybrid shielding/magnetic bias product\n\n[39:34] Printed vapour cells\n\n[41:34] Spectroscopy and magnetic sensors\n\n[42:36] Compact\, printed Laser system\n\n[44 :22] A printed gravimeter f or space\n\n[46:16] Pri nted cold atom system\n\n[49:35] Where to next?\n\n[53:42] Other ideas on the horizon?\n\n[58:02] What current work in cold atoms is interestin g but underappreciated?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/83/ END:VEVENT BEGIN:VEVENT SUMMARY:Elisabeth Krause++ (University of Arizona) DTSTART:20240606T060000Z DTEND:20240606T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/84 DESCRIPTION:Title: The Parameter Masked Mock Data Challenge for Beyond 2-Pt Statistic s - Results\, Lessons & Reflections\nby Elisabeth Krause++ (University of Arizona) as part of Cosmology Talks\n\n\nAbstract\n1-1/2 hour discussi on with Shaun Hotchkiss and 9 members of The Beyond-2pt Collaboration: Eli sabeth Krause\, Marcos Pellejero-Ibanez\, Andres Salcedo\, Minh Nguyen\, M ikhail Ivanov\, Enrique Paillas\, Carolina Cuesta-Lazaro\, Chirag Modi\, G iovanni Verza\n\nOne-sentence summary of the work by Minh Nguyen: "how cos mology and galaxy survey analyses can move beyond the canonical 2-point co rrelation function"\n\nRecorded video: youtu.be/LPykO2206OY\n\nPaper: arXiv:2405.02252\n\n
\n\nIndex to Key Parts of the Talk< /b>\n\n[0:00:00] Shaun's intro \n\n[0:02:05] Opening co mments by Elisabeth Krause\n\n[0:03:13] Two things to remember about this talk\n\n[0:04:56] The history of this idea\n \n[0:06:19] Why the team use d this approach\n\n[0:08:43] Getting into the details\n\n[0:13:31] Redshift-space results in σ8 and Ωm (Figs. 21\, 1 in paper)\n\n[0:18:10] Lig ht-cone and Real-space Results (Figs 3\, 4)\n\n[0:19:28] Takeaways\n\n[0:22:53] The Methods and How They Work: Participa ting Analyses (Table 1)\n\n[0:24:14] Importance of k_max\n\n[0:27:18] Overview of EFT Methods\n\n[0:35:47] Overview of HOD Methods\n\n[0:41 :43] 2-min overviews of eac h specific method\n\n[0:55:50] Post unmasking insights and updated results\n\n[1:04:49] Lessons learned and future refle ctions\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/84/ END:VEVENT BEGIN:VEVENT SUMMARY:Tamara Davis\, Maria Vincenzi\, Dillon Brout (DES Collaboration) DTSTART:20240610T060000Z DTEND:20240610T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/85 DESCRIPTION:Title: The Dark Energy Survey Supernova Program - Data and Cosmology\ nby Tamara Davis\, Maria Vincenzi\, Dillon Brout (DES Collaboration) as pa rt of Cosmology Talks\n\n\nAbstract\nTamara Davis\, Maria Vincenzi and Dil lon Brout tell us about the Dark Energy Survey's (DES) new supernova catal ogue. The catalogue has more than 1500 new supernovae\, and will allow a v ast range of new cosmology constraints. It is a factor of around five larg er than the next largest high redshift supernovae catalogue.\n\nVery curio usly\, DES' supernovae see hints of evolving dark energy. This is especial ly curious given that a few months after DES released this data\, the Dark Energy Spectroscopic Instrument (DESI) also released data with similar hi nts.\n\nTamara: s mp.uq.edu.au - tamara-davis\n\nMaria: linkedin - maria-vincenzi\n\nDillon: < a href="https://djbrout.github.io/">djbrout.github.io\n\nKey cosmology paper: arXiv: 2401.02929\n \nCosmological Analysis and Systematic Uncertainties: arXiv: 2401.02945\n\nLight curves and 5-Year da ta release: arXiv: 2406.05046\n\n
\n\nIndex to Key Parts of the Talk\n\n[0:00:00] Shaun's intro\n\n[0:01:11] Intro by the 3 speakers to this work\n\n[0:02:43] Two takeaways to remember\n\n[0:05:54] Supernova cosmology basics\n\n[0:29:47] DES Analysis Details\n\n[0:48:10] DES SN Cosmology Results\n\ n[1:00:09] Is dark energy a cosmological constant? \n\n[1:01:22] A few months later...DESI supports DES\, finding similar resu lt for wa\n\n[1:02:39] Big Questions: Is the expansion of the Universe accelerating? Ye s! \n\n[1:03:35] Big Que stions: Is dark energy a cosmological constant? Maybe? Union 3 also prefer w > -1\n\n[1:10:23] Big Questions: How old is the Universe? Slightly younger than we thought?\n\n[1:11:12] Big Questions : Does DES best fit resolve Hubble tension? No\, DES doesn't constrain H0\n\n[1:12:04] Bonus Science!!!\n\n[1:16:08] Cosmology work interesting but underappreciated?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/85/ END:VEVENT BEGIN:VEVENT SUMMARY:Ryan Camilleri\, Tamara Davis (DES Collaboration\, University of Q ueensland) DTSTART:20240611T060000Z DTEND:20240611T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/86 DESCRIPTION:Title: DES Supernovae - H0 From the Inverse Distance Ladder Without ΛCDM \nby Ryan Camilleri\, Tamara Davis (DES Collaboration\, University of Queensland) as part of Cosmology Talks\n\n\nAbstract\nRyan Camilleri and T amara Davis tell us about how they have used the Dark Energy Survey's Year 5 supernovae catalogue\, anchored to the Dark Energy Spectroscopic Instru ment's Baryon Acoustic Oscillations\, to create an "inverse distance ladde r".\n\nWith this they are able to determine the Hubble Parameter\, at reds hift zero with a high accuracy\, without needing to assume ΛCDM. The resu lts still match Planck\, meaning that the high redshift to low redshift ma tching appears to still not work out\, even outside of ΛCDM.\n\nThe impli cations are large for any attempts to go beyond ΛCDM to solve the Hubble tension as it appears the z=2 to z=0.05 window is not the right window for finding the solution.\n\nVideo recording: youtu.be/kzT0tWWggRo\n\nPaper: arXiv: 2406.05049\n\nRyan: smp.uq.edu.au/profile/13102/ryan-camilleri\n\nTamara: smp .uq.edu.au/profile/186/tamara-davis\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/86/ END:VEVENT BEGIN:VEVENT SUMMARY:Ryan Camilleri\, Tamara Davis (DES Collaboration\, University of Q ueensland) DTSTART:20240612T060000Z DTEND:20240612T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/87 DESCRIPTION:Title: DES Supernovae - Beyond ΛCDM\nby Ryan Camilleri\, Tamara Davi s (DES Collaboration\, University of Queensland) as part of Cosmology Talk s\n\n\nAbstract\nRyan Camilleri and Tamara Davis tell us about how they ha ve examined models beyond ΛCDM using the Dark Energy Survey's wonderful s upernova catalogue. Tantalisingly\, they find that a number of models are "moderately preferred" over ΛCDM (in model comparison speak).\n\nThey als o\, very admirably\, check whether crucial aspects of the DES pipeline are model dependent or not. They find that\, so long as the reference model i s close-ish to the true model then the pipeline is accurate. "Close-ish" i s very generous here as well\, as they even found in simulations that when one processed the data with models 10σ from the truth\, the subsequent p arameter constraints were still within 1σ of the truth. The moral of this is that\, even though the supernovae were processed assuming ΛCDM\, so l ong as the true cosmology isn't too far from ΛCDM then this doesn't matte r.\n\nThis means\, if you have your own model that they haven't tested\, y ou don't need to simulate the entire DES analysis pipeline to analysis you r model\, you can do your model comparison at the level of the Hubble diag ram. Nice!\n\nTalk video: youtu.be/ NLXxX-Z2OfM\n\nPaper: arXiv : 2406.05048\n\nRyan: smp.uq.edu.au/profile/13102/ryan-camilleri\n\nTamara: smp.uq.edu.au/profil e/186/tamara-davis\n\n
\n\nIndex to Key Parts of the Talk\n\ n[00:00] Shaun's intro\n\n [01:41] Opening comments by Ryan\n\n[02:20] Two take aways to remember\n\n[03:06] Motivation for this work\, starting with ΛCDM overview\n\n[05:01 ] So why go beyond ΛCDM?\n\n[06:13] What is beyond ΛCDM? Testing different models\n\n[07:18] Parametric forms of Λ\n\n[09:28] Dvali-Gabadadze-Porrati (DBP) models\n\n[ 10:04] Chaplygin Gas models< /a>\n\n[11:13] Timescape cos mology\n\n[14:12] Why th ese models were tested vs other options?\n\n[15:31] Observations -> Hubble Diagram\n\n[16:08] DES-SN5YR Pipeline\n\n[2 3:10] The Omega\\_m - w deg eneracy\; intro of Q_H parameter\n\n[25:21] Model constraints\n\n[29:43] Model comparisons\n\n[35:37] What's next?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/87/ END:VEVENT BEGIN:VEVENT SUMMARY:Paul Shah\, Tamara Davis (DES Collaboration\, University College L ondon\, University of Queensland) DTSTART:20240617T060000Z DTEND:20240617T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/88 DESCRIPTION:Title: DES Supernovae - Weak Lensing Magnification Detected at 6σ!\n by Paul Shah\, Tamara Davis (DES Collaboration\, University College London \, University of Queensland) as part of Cosmology Talks\n\n\nAbstract\nPau l Shah and Tamara Davis tell us about how they have used this wonderful su pernova catalogue from the Dark Energy Survey to detect the weak lensing m agnification signal for the first time. There has been evidence of this si gnal in earlier catalogues\, but at no bigger than 1.4σ. They've got it a t 6σ!\n\nThey do this by correlating the scatter in the magnitude of the supernovae with the over-under density in galaxy catalogues along the same lines of sight of the supernovae. Where there is more matter\, the light from the supernova should be magnified\, and where there is less matter it should be de-maginified. And they do indeed see that along overdense line s of sight the supernovae are\, on average\, ever so slightly brighter\, a nd on underdense lines of sight the are ever so slightly dimmer.\n\nI can' t wait to see how this observable is used in the future to constrain all s orts of bits of cosmology. Nice work everyone!\n\nTalk Video: youtu.be/YljnmVZKukc\n\nPaper: arXiv: 2406.05047\n\nPaul: paulshah.github.io\n\nTamara: smp.uq.edu.au/profile/186/tamar a-davis\n\n
\n\nIndex to Key Parts of the Talk\n\n[00:00] Shaun's intro\n\n[01:20] Searching for gravitational lens ing of SNe\n\n[04:24] Tw o takeaways to remember\n\n[05:43] Motivation for this work and why it could be done now\n\n[1 0:22] The Hubble diagram of SN Ia\n\n[11:16] What do es a clumpy universe do to SN Ia?\n\n[13:37] But can we detect it?\n\n[14:46] Our data\n\n[16:37] Our lensing estimator\n\n[20:52] Correlate lensing estimate with Hubble diagram residuals\n\n[27:01] The shape of dark matter haloes\n\n[27:43] 'Adaptive optics' for dark matter\n\n[30:49 ] What's next?\n\n[34:2 3] Key results from DES-SN5 YR weak lensing\n\n[45:05] Further work anticipated?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/88/ END:VEVENT BEGIN:VEVENT SUMMARY:Ryan White\, Tamara Davis (DES Collaboration\, University of Queen sland) DTSTART:20240619T060000Z DTEND:20240619T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/89 DESCRIPTION:Title: DES Supernovae - Precisely Measured Time Dilation from Universe's Expansion\nby Ryan White\, Tamara Davis (DES Collaboration\, Universit y of Queensland) as part of Cosmology Talks\n\n\nAbstract\nRyan White and Tamara Davis from the Dark Energy Survey tell us about how they have measu red time dilation in distant supernovae. This time dilation is precisely w hat one would expect in an expanding universe. "Precisely" is the right wo rd too\, as they have measured this effect to 0.5% precision and they get exactly the number predicted by an expanding universe.\n\nThere may be all sorts of tensions popping up for the standard cosmological model ΛCDM\, but it seems the expanding universe itself is doing just fine.\n\nTalk vid eo: youtu.be/1vfo-JFc-Io\n\nRya n: ryanwhite1.github.io\n\nTam ara: smp.uq.edu.a u/profile/186/tamara-davis\n\nThe paper: arXiv: 2406.05050\n\nThe paper with the \\Delta t = (1+z ) proof (in appendix A): arXiv: 0804.3595\n\n
\n\nIndex to Key Parts of the Talk\n\n[00:00] Shaun's intro\n\n[02:46] < a href="https://youtu.be/1vfo-JFc-Io?t=166s">Overview of this work by Ryan and Tamara\n\n[06:08] S upernova light curves in different bands across redshifts\n\n[10:55] < a href="https://youtu.be/1vfo-JFc-Io?t=655s">Picking similar light curves out of different bands\n\n[11:23] Stacked light curves\n\n[13:55] Scale light curves in time by function of source z\n \n[18:02] The 'width' of ea ch individual light curve\n\n[18:43] Quantifying time dilation\n\n[21:44] Why do we expect time dilation?\n\n[27:58] Scatter in widths from noi se & intrinsic SN light curve variation\n\n[38:00] Where to next?\n\n[40:56] What current cosmology work is interesting but underappreciated?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/89/ END:VEVENT BEGIN:VEVENT SUMMARY:Wendy Freedman\, Barry Madore (Chicago Carnegie Hubble Program (CC HP)) DTSTART:20240816T060000Z DTEND:20240816T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/90 DESCRIPTION:Title: The Status of the Chicago-Carnegie Hubble Program (with JWST data) \nby Wendy Freedman\, Barry Madore (Chicago Carnegie Hubble Program (C CHP)) as part of Cosmology Talks\n\n\nAbstract\nWendy Freedman and Barry M adore give a status update on the Chicago-Carnegie Hubble Program (CCHP). There has been much progress!\n\nIn this status update there are three ind ependent distance ladder measurements of the expansion rate (i.e. the Hubb le parameter) all using JWST data. There is the very well-known Cepheid me thod\, the now also well known Tip of the Red Giant (TRGB) method\, and ma king its debut\, the J-Region Asymptotic Giant Branch (JAGB) method. \n\nT he TRGB and JAGB methods agree strikingly well and appear to be consistent with the CMB + ΛCDM value for the expansion rate. The Cepheid method als o agrees to within less than 5%\, which is still striking\, but there is s ome deviation.\n\nThe deviation pushes the Cepheid value for H0 up\, makin g it consistent with the SH0ES value\, although the error bars on this CCH P result are large enough that their Cepheid value is also consistent with the lower TRGB and JAGB methods. Most curiously (to this relative outside r) the JAGB value does not appear to be consistent with SH0ES\, even when considering statistical and systematic errors at once. The striking consis tency between TRGB and JAGB\, means that one's naive guess might be that t here is some unknown systematic in the Cepheid method (in both the CCHP an d SH0ES measurements). However\, naive guesses are naive so\, time will te ll.\n\nTime really will tell as the ongoing JWST measurements w ill shrink both statistical and systematic errors in all methods\, so it w on't be long before the CCHP Cepheids are forced to take a side.\n\nVideo recording: youtu.be/OkGUoKukwk8 \n\nWendy: astro.uchicago.edu/people/wendy-l-freedman.php\n\nBarry: carnegiescience.ed u/bio/dr-barry-madore-emeritus\n\nPaper: arXiv: 2408.06153\n\n
\n\n[0:00:00] Intro comments by Shaun and Wendy\n\n[0:01: 22] Two takeaways to remember \n\n[0:01:47] Not seeing now *extraordinary evidence* for Hubble tension\; unknown systematics \n\n[0:03:18] Background on gold standard methods for measuring H0\n\n[0:09:05] 2 methods agree in their zero point\, low scat ter against each other\n\n[0:09:35] 2 new papers on arXiv and recent CCHP group papers\; more comi ng\n\n[0:11:58] First ta rget galaxies\; TRGB and JAGB advantages\; HST cf JWST\n\n[0:20:54] 3 distances indicators - TRGB \, Cepheids\, JAGB\n\n[0:29:14] JAGB details\n\n[0:31:29] Data Analysis\n\n[0:32:31] Comparison of distances (pre a determination of H0)\n\ n[0:36:09] TRGB vs JAGB com parison\n\n[0:38:22] SN Calibrator M_B with Distance Modulus (potential systematic needs understa nding)\n\n[0:42:02] Car negie Supernova Project\n\n[0:44:12] Summary of H0 Values and Statistical Uncertainties (Table 4 in paper)\n\n[0:51:09] Distribution of H0 Values for 3 JWST Methods( Fig. 11)\n\n[0:52:45] Distribution of H0 Values Wit h Total Errors (Fig. 12)\n\n[0:53:21] CCHP JWST H0 Values (Fig. 20)\n\n[0:58:38] Conclusions (TRGB\, JAGB agree at 1% le vel\; results consistent with Planck\, LCDM\n\n[1:02:27] What might be cause of high H0 with Ceph eids?\n\n[1:06:28] What about the possibility of new physics?\n\n[1:09:06] What current work in cosmology is interesting but underappreciated?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/90/ END:VEVENT BEGIN:VEVENT SUMMARY:Abigail J. Lee (University of Chicago) DTSTART:20240822T060000Z DTEND:20240822T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/91 DESCRIPTION:Title: Extragalactic Distances from the J-region Asymptotic Giant Branch< /a>\nby Abigail J. Lee (University of Chicago) as part of Cosmology Talks\ n\n\nAbstract\nAbigail Lee tells us about how she has used the J-region As ymptotic Giant Branch (JAGB) to measure extragalactic distances\, ultimate ly using them as a rung on the distance ladder to measure the expansion ra te of the universe.\n\nThe JAGB method is new\, at least compared to cephe ids and "tip of the red giant" (TRGB) methods\, but is also very promising . The stars it uses are bright\, so they can be seen at large distances\, and they're numerous\, which means they can be observed far from the centr es of galaxies (minimising "crowding" from other stars in the same pixels) . So\, even ignoring Hubble tensions\, this is a very exciting time to be involved in extragalactic distance measurements.\n\nAbby used data from J WST to detect the JAGB mode brightness\, which is then the distance indica tor of the method. With more telescope time\, and more local calibrators\, JAGB will only go from strength to strength.\n\nWhen the measured distanc es are compared to JWST measurements of TRGB and cepheids it has very litt le scatter with TRGB\, but a little more from cepheids. The ultimate Hubbl e parameter is also on the smaller side\, consistent with CMB + ΛCDM and on the border of being inconsistent with SH0ES cepheid+HST based measureme nts.\n\nTalk video: youtu.be/mpSsmy InrEA\n\nAbby: abiglee7.github.i o\n\nThe paper: arXiv: 2408 .03474\n\nAlso see recent\, related Cosmology Talk with Wendy Freedman and Barry Madore at youtu.be/OkGUo Kukwk8\n\n
\n\n[00:00] Intro comments by Shaun\n\n[01:06] Abby's opening comments on paper and CCHP\n\n[01:37] Two takeaways to remember\n\n[02 :36] Background and motivati on for this work\n\n[04:50] Asymptotic Giant Branch Stars \, HR diagram\, carbon stars as standard candles\n\n[06:38] The J-Region Asymptotic Giant Branch (JAGB) Method\n\n[08:30] History of the JAGB Method\n\n[17:08 ] Comparison of brightnesse s between distance indicators\n\n[18:58] The JAGB Method Advantages\n\n[20:25] TRGB\, Cepheids\, and JAGB are independen t methods\n\n[22:45] Ho w accurate/precise are JAGB distances vs TRGB and Cepheids?\n\n[25:38] Comments on the paper\ n\n[30:32] How do you know where the outer disk is?\n\n[33:32] Final H0 and Distance Comparisons\n\n[37:21] Summary\n\n[37:57] Is JAGB the gold standard method of the fut ure?\n\n[43:36] What cu rrent work in cosmology is interesting but underappreciated?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/91/ END:VEVENT BEGIN:VEVENT SUMMARY:Ana Alexandre\, Valentin Thoss (Max Planck Institute for Physics) DTSTART:20240921T060000Z DTEND:20240921T070000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/92 DESCRIPTION:Title: A New Window for PBH Dark Matter (Due to Delayed Hawking Radiation )?\nby Ana Alexandre\, Valentin Thoss (Max Planck Institute for Physic s) as part of Cosmology Talks\n\n\nAbstract\nAna Alexandre and Valentin Th oss tell us about their recent papers examining the consequences of a pote ntial "memory burden" effect on decaying primordial blackholes (PBHs). \n\ nThis memory burden effect would be a consequence of quantum gravity and w ould substantially slow down the Hawking evaporation of blackholes. The co nsequences for primordial blackholes would be very important because it wo uld open a whole window of PBH masses as dark matter candidates. (Masses t hat are normally ignored because PBHs of these masses are presumed to have decayed by today.)\n\nAll fundamental physicists would agree that Hawking radiation must breakdown at some point at/before a blackhole reaches the Planck mass. This proposed memory burden effect goes a step further and cl aims that the breakdown must happen no later than when a blackhole has dec ayed to half of its original mass. This is not universally agreed upon\, b ut it's still worth examining the consequences if it is true.\n\nRecorded video: youtu.be/p8UhnWri4II\n\n Ana: at link edin
\nValentin: at Max Planck Inst\n\nAna's paper: arXiv: 2402.14069
\nValentin's paper: arXiv: 2402.17823\n\n
\n\n[00:00] Intro comments by Shaun\n\n[01:30] Brief opening comments by Valent in\n\n[02:18] Two takeawa ys to remember by Ana\n\n[02:50] Getting into the background\n\n[07:45] Black hole evaporation\; "memory burden" effect\ n\n[14:32] How well accepted is the memory burden effect by experts in its field?\n\n[17:34] New parameter space for PBH DM \n\n[21:06] Big Bang Nucleos ynthesis\n\n[22:24] Rela xing constraints with memory burden\n\n[26:51] 4 Constraints (sections 2.5-2.8 in 2402.17823)\ n\n[27:41] Constraints from galactic gamma ray emission\n\n[32:22] The other 3 constraints\n\n[37:42] The landscape of constraints\n\n[38:53] Combined constraints plot (Fig. 1 in 2402.17823)\n\n[42:18] Discussion re lower bound on the mass\n\n[43:40] Where to next?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/92/ END:VEVENT BEGIN:VEVENT SUMMARY:Daniele Sorini (Durham University) DTSTART:20241113T050000Z DTEND:20241113T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/93 DESCRIPTION:Title: How Dark Energy Affects Past and Future Star Formation\nby Dan iele Sorini (Durham University) as part of Cosmology Talks\n\n\nAbstract\n Daniele Sorini tells us about his research looking into how the value of d ark energy affects star formation in the universe. He builds an analytic m odel of star formation in the universe\, which allows him to follow the un iverse to very late times and ask "if Λ was different\, how many total st ars could form over the entire history of the universe?"\n\nThis is the cr ucial question one wants to ask when examining anthropic explanations of Λ scientifically. Previous studies have asked this question using simulat ions\, forcing them to stop after a finite amount of time.\n\nFascinatingl y\, Daniele finds that there is a value of Λ where star formation peaks\, which is about 0.1 times the value in our universe. Previous simulation-b ased studies maybe didn't spot this because they simply didn't do simulati ons with Λ less than our observed value\, except for Λ=0\, but also they didn't go to late enough times.\n\nWhen combined with a uniform prior for Λ he finds that our value\, or a value smaller than it still only has a 0.5% chance\, but with other priors one gets other results.\n\nTalk video: youtu.be/cgfV2vwtEgs\n\nThe pa per: arXiv: 2411.07301\n\nD aniele: danielesorini.com\n\n
\n\nIndex to Key Parts of the Talk\n\n[0:00:00] Intro comments by Shaun\n\n[0:0 1:13] Brief opening comments by Daniele\n\n[0:02:09] Sneak preview of the results\n\n[0:05:07] What was surprising about the results?\n\n[0:07:24] Motivation and current relev ance for this work\n\n[0:15:59] Can ΛCDM explain observations?\n\n[0:27:03] Diff models reach diff conclusions but all p osteriors peak at Λ>>Λobs\n\n[0:29:53] Details\n\n[0:36:48] Improved match with observations of cosmic SFR density vs time\n\n[0:39:25] Stell ar mass density converges as time tends to infinity\n\n[0:41:18] Star formation saturates at t>>1 00 Gyr (Fig 9 in paper)\n\n[0:49:31] Larger Λ -> Fewer massive haloes (Fig 4)\n\n[0:50:20] < a href="https://youtu.be/cgfV2vwtEgs?t=3020s">Larger Λ -> More efficient haloes (Fig 8)\n\n[0:55:56] Does Λ=Λobs promote the generation of observers? (Fig 11)\n\n[0 :58:14] Conclusions very se nsitive to prior on Λ (Fig 12)\n\n[1:01:27] Conclusions\n\n[1:09:25] Where to next?\n\n[1:17:20] What current cosmology work is interesting bu t underappreciated by the community?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/93/ END:VEVENT BEGIN:VEVENT SUMMARY:Arnaud de Mattia\, Héctor Gil-Marín\, Pauline Zarrouk (DESI Coll aboration) DTSTART:20241120T050000Z DTEND:20241120T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/94 DESCRIPTION:Title: DESI 2024: Cosmology Results from the Power Spectrum's Full Shape< /a>\nby Arnaud de Mattia\, Héctor Gil-Marín\, Pauline Zarrouk (DESI Coll aboration) as part of Cosmology Talks\n\n\nAbstract\nArnaud de Mattia\, He ctor Gil-Marín and Pauline Zarrouk tell us about the latest DESI key pape rs. These ones are covering the "full shape" of the galaxy power spectrum. This is in contrast to their results from April\, which were centred arou nd the Baryon Acoustic Oscillation (BAO) feature.\n\nThe analysis is an ab solute tour de force\, explaining why the video is so long. DESI have done a lot of analysis and it takes a while to unpack. (The raw recording of t his video was more than 200 minutes long!)\n\nThe results aren't quite so eye-opening as the BAO ones were in April. The evidence for evolving dark energy is still there\, but the significance of this evidence hasn't chang ed much. They are however able to do a bunch of tests of modified gravity and find that\, unlike ΛCDM\, General Relativity appears to be in great s hape (at least as far as DESI observations are concerned).\n\nWe're proper ly in the era of Stage 4 cosmology now! Thanks DESI for the wonderful anal yses and results.\n\nTalk video recording: youtu.be/2mlU-YzEbw\n\nRelevant papers on the a rXiv:
\n2411.12026 - Mod ified Gravity Constraints from the Full Shape Modeling of Clustering Measu rements from DESI 2024
\n241 1.12025 - Characterization of DESI fiber assignment incompleteness eff ect on 2-point clustering and mitigation methods for DR1 analysis
\n2411.12024 - Mitigating Imagin g Systematics for DESI 2024 Emission Line Galaxies and Beyond
\n2411.12023 - Exploring HOD-depende nt systematics for the DESI 2024 Full-Shape galaxy clustering analysis
\n2411.12022 - DESI 2024 VI I: Cosmological Constraints from the Full-Shape Modeling of Clustering Mea surements
\n2411.12021 - DESI 2024 V: Full-Shape Galaxy Clustering from Galaxies and Quasars
\n 2411.12020 - DESI 2024 II: Sample Definitions\, Characteristics\, and Two-point Clustering Statistics
\n\nArnaud: inspirehe p.net/authors/1881382
\nHector: www.ub.edu/bispectrum
\nPauline: inspirehep.net/authors/1884383
\n\nDESI itself : desi.lbl.gov
\n\nTimestamp li nks to key parts of the talk:
\n00:00 Intro and brief overview of new result s
\n0 6:12 The background and motivation
\n24:05 Full shape galaxy clusterin g analysis
\n55:46 Systematic effects
\n1:10:10 Cosmology results!
\n1:19:28 Beyond ΛCDM and GR constraints
\n1:37:02 Conclusions and additional di scussion
\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/94/ END:VEVENT BEGIN:VEVENT SUMMARY:Guadalupe Cañas Herrera\, Hervé Aussel (Euclid Consortium) DTSTART:20250319T050000Z DTEND:20250319T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/95 DESCRIPTION:Title: Euclid 2025: Science Goals and Q1 Data Summary\nby Guadalupe C añas Herrera\, Hervé Aussel (Euclid Consortium) as part of Cosmology Tal ks\n\n\nAbstract\nThe day has arrived. The space observatory Euclid is pro ducing and sharing results. In this video Guadalupe Cañas-Herrera and Her vé Aussel tell us about Euclid\, its science goals and the Q1 data set th ey have released today.\n\nTalk video recording\n\nEuclid Papers\n\nEuclid Consortium det ails on the Q1 release\n\nESA details on the Euclid Q1 release\n\n
\n\nIndex to Key Parts of the Talk\n\n[01:18] Euclid overview\n\n[02:21] Euclid: intro and goals\; dark energy\, accele rated expansion\, dark matter\n\n[04:38] Why the name Euclid?\n\n[06:28] Universe timeline\; Euclid targets 0 < z < 3 to s tudy LSS and create 3D map\n\n[08:58] Two probes: cosmic shear and galaxy clustering\n\n[12:35 ] Mapping the Universe in 3D \n\n[13:05] Euclid space craft and instrument details\n\n[18:46] Scope of the Euclid Wide Survey\n\n[19:59] What to Expect\n\n[20:50] Advantages of Euclid as a space mi ssion\n\n[22:06] Outloo k for constraints on w\\_0 and w\\_a\n\n[23:40] Q1 Data Release Contents\n\n[26:06] The Euclid Deep Fields\n\n[30:16 ] Q1 Processing\n\n[33: 32] Photometric Redshifts a nd Photometric Classification\n\n[34:55] Physical Parameters\n\n[36:31] NISP Spectroscopy\n\n[40:16] SPE Redshifts Measurements\n\n[47:13] Important Caveats\n\n[5 0:54] Conclusion\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/95/ END:VEVENT BEGIN:VEVENT SUMMARY:Teresa Matamoro\, Mike Walmsley\, Phil Holloway (Euclid Consortium ) DTSTART:20250319T050000Z DTEND:20250319T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/96 DESCRIPTION:Title: Euclid 2025: AGN\, Galaxy Morphology & Strong Lensing\nby Tere sa Matamoro\, Mike Walmsley\, Phil Holloway (Euclid Consortium) as part of Cosmology Talks\n\n\nAbstract\nTeresa Matamoro\, Mike Walmsley and Phil H olloway tell us about three key areas Euclid has shed a scientific light o n in their Q1 data release today. These are active galactic nuclei\, galax y morphology and strong lensing.\n\nTalk video recording\n\nEuclid Papers\n\nEuclid Conso rtium details on the Q1 release\n\nESA details on the Euclid Q1 release\n\nPapers:\n\n[2503.15326] Euclid Quick Data Release (Q1). The Strong Lensing Discove ry Engine C - Finding lenses with machine learning\n\n[2503.15324] Euclid Quick Data Release (Q1): Th e Strong Lensing Discovery Engine A -- System overview and lens catalogue< /a>\n\n[2503.15320] Euclid Quic k Data Release (Q1). The active galaxies of Euclid\n\n[2502.06505] Euclid: A complete Einstein ring i n NGC 6505\n\n[2404.02973] Scaling Laws for Galaxy Images\n\n
\n\nTimestamp Index to Key Pa rts of the Talk\n\n[00:00:00] Shaun's intro\n\n[00:01:03] AGN overview (Teresa)\n\n[00:05:47] New results and main takeaways\n\n[00:09:43] Building a multi-wavelength catalo gue\n\n[00:13:54] Colour -colour selections\n\n[00:17:31] Spectroscopy\n\n[00:18:51] SED fitting\n\n[00:20:32] Other AGN works\n\n[00:21:22] What next?\n\n[00:22:38] Application to cosmology (Mike)\n\n[00:23:44 ] Galaxy morphology\n\n [00:31:34] What are foundat ion models?\n\n[00:38:08] Strong lensing (Phil)\n\n[00:42:01] 497 strong lenses found in Euclid Q1\n\n[00:44:29] Euclid will revolutionise stro ng lensing\n\n[00:47:33] The Euclid Strong Lensing Discovery Engine\n\n[00:54:43:] Which lenses did we find?\n\n[00: 57:28] Notable lens candida tes\n\n[01:02:49] With 100k future strong lenses\, any possibility of GR tests?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/96/ END:VEVENT BEGIN:VEVENT SUMMARY:Cristhian Garcia Quintero\, Paul Martini (DESI Collaboration) DTSTART:20250319T050000Z DTEND:20250319T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/97 DESCRIPTION:Title: Cosmology Results from DESI DR2 BAO\nby Cristhian Garcia Quint ero\, Paul Martini (DESI Collaboration) as part of Cosmology Talks\n\n\nAb stract\nCristhian Garcia Quintero and Paul Martini tell us about the baryo n acoustic oscillation measurements in data release two (DR2) of the Dark Energy Spectroscopic Instrument (three years of data). As with the first d ata release they are seeing evidence for evolving dark energy. They now se e it when combining with just CMB\, or with "just" Dark Energy Survey supe rnovae and clustering data.\n\nTalk Recording: youtube.com/watch?v=YiRaDtslycE\n\nCristhia n Garcia Quintero: gqcristhian.gi thub.io\n\nPaul Martini: OSU.edu\n\nGuide to DESI DR2 Results\, dated 19-Mar-2025 \n\nRelevant papers on the arXiv:\n\n[2503.14738] DESI DR2 Results II: Measurements of Baryon Acousti c Oscillations and Cosmological Constraints\n\n[2503.14739] DESI DR2 Results I: Baryon Acoustic Oscil lations from the Lyman Alpha Forest\n\n[2503.14741] Validation of the DESI DR2 Ly$α$ BAO analysis us ing synthetic datasets\n\n[ 2503.14742] Validation of the DESI DR2 Measurements of Baryon Acoustic Osc illations from Galaxies and Quasars\n\n[2503.14743] Extended Dark Energy analysis using DESI DR2 BAO measurements\n\n[2503.14744 ] Constraints on Neutrino Physics from DESI DR2 BAO and DR1 Full Shape \n\n
\n\nTimestamp Index to Key Parts of the Talk\n\n[00:00:00] Shaun's intro\n\n[00:00:54 ] Overview of findings\n\ n[00:02:53] Main plot of res ults with and w/o supernova datasets\n\n[00:03:46] The highest significance plot and the role of D ES Y5 data\n\n[00:04:40] w0wa parameterization vs physical models beyond LCDM\n\n[00:07:55] Getting deeper into the backg round\n\n[00:09:14] The BAO scale as a "standard ruler"\n\n[00:14:00] Mystery of Cosmic Acceleration slide\n\n[00:15:1 8] Getting into details of B AO measurements from DESI DR2\n\n[00:17:10] Transition from DESI DR1 to DR2\n\n[00:18:43] DESI Data Release 2\n\n[00 :20:13] Correlation functio n measurements\n\n[00:28:16] DESI LyA Measurement\n\n[00:32:50] DESI LyA BAO Measurement\n\n[00:38:59] Cosmological constraints under LCDM\n \n[00:50:33] Omega_m under w 0waCDM\n\n[00:51:25] Con straints on evolving dark energy\n\n[00:58:45] Robustness of the DE results\n\n[01:03:38] Binning the DE equation of state \n\n[01:06:50] DESI and neutrino mass\n\n[01:11:00] Future outlook\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/97/ END:VEVENT BEGIN:VEVENT SUMMARY:Wright\, Stölzner\, Reischke\, Asgari\, Kuijken (Kilo-Degree Surv ey (KiDS)) DTSTART:20250326T050000Z DTEND:20250326T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/98 DESCRIPTION:Title: KiDS­ Legacy - The Final Cosmology Results\nby Wright\, Stöl zner\, Reischke\, Asgari\, Kuijken (Kilo-Degree Survey (KiDS)) as part of Cosmology Talks\n\n\nAbstract\nAngus Wright\, Benjamin Stölzner\, Robert Reischke\, Marika Asgari and Konrad Kuijken tell us about the final cosmol ogy results from the Kilo Degree Survey (KiDS-Legacy). After exhaustive im provement of their analysis\, and consistency tests\, and a six month wand er in the B-Mode wilderness they emerge with no S8 tension at all.\n\nTalk Video Recording: youtu.be/PIQKe-tW 1xQ\n\nAngus: anguswright.git hub.io\n\nBenjamin: i nspirehep.net/authors/1944983\n\nRobert: inspirehep.net/authors/2219647\n\nMarika: ncl .ac.uk/...\n\nKonrad: universiteitleiden.nl/...\n\nPapers: \n\n2503.19442\n\n2503.19441\n\n2503.19440\n\n
\n\nIndex to Key Parts o f Talk\n\n[00:00:00] Shaun 's intro\n\n[00:01:00] Ov erview and main cosmological constraints\n\n[00:04:11] Internal Consistency Constraints\n\n[00 :05:15] The early vs late de bate\n\n[00:07:20] Bluep rint for Stage-IV\; Why now? Why not sooner?\n\n[00:10:26] Since 2021: Updated calibrations\, samp les\, and area\n\n[00:20:00] Details of KiDS Legacy analysis: Redshift Calibration\n\n[00:27: 43] Covariance and modellin g\n\n[00:33:51] Updated Astrometric Calibration\n\n[00:36:17] B-modes issue\n\n[00:43:05] Internal Consistency\n\n[00:54:20] Consistency motivates further joint analy ses\n\n[01:00:21] What' s next? Onwards to Stage-IV\n\n[01:02:23] What's underappreciated by the community in current cos mology work?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/98/ END:VEVENT BEGIN:VEVENT SUMMARY:Sankarshana Srinivasan (Ludwig-Maximilians Universitat) DTSTART:20251107T050000Z DTEND:20251107T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/99 DESCRIPTION:Title: Cosmological Gravity on All Scales\nby Sankarshana Srinivasan (Ludwig-Maximilians Universitat) as part of Cosmology Talks\n\n\nAbstract\ nSankarshana Srinivasan tells us about his work building the framework to constrain (or detect!) modified gravity using upcoming surveys. Building o n earlier work developing model independent modified gravity simulations\, Shankar now shows how a clever transform (the BNT transform) is able to b etter isolate the weak-lensing kernel\, meaning one can more cleanly cut o ut the fully messy non-linear scales without losing too much usable inform ation. We're all looking forward to the talk in 3-5 years' time applying t hese methods to Euclid and LSST data!\n\nPaper: arXiv: 2409.06569\n\nTalk video: youtube.com/watch?v=nIdCpcObSVU\n\nC osmology Talk on earlier work in this series by Dan Thomas: The first model independent cosmol ogical simulations of modified gravity\n\nIndex to Key Parts of the Talk\n\nShaun's intro \n\nShankar's brief overview on the paper\n\nA key in sight: mitigating baryonic feedback\n\nA physical intuition on mu μ and eta η parameters\n\n Binning strategies\n\nSome Problems with ΛCDM\n \nVast model space\n\nPost-Friedmann Formalism: Pix elized Poisson Equation\n\nN-body simulations: Measuring P(k) for binned μ\n\nN-body simulations: ReACT for binned μ\n\nN-body simulations: C omputing 3x2pt observables\n\nFisher Forecasts\n\nFisher Forecasts: Key questions\n\nThe Bernardeau-Nimishi-Taruya (BNT) Transform\n\nMitigating Baryonic Feedback \n\nWhere does the constrai ning power come from?\n\nAdding the concentration fit\n\nWhat next?\n\nSummary slide points (but no discussion)\n\nWhat current work in cosmology is interesting but u nderappreciated?\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/99/ END:VEVENT BEGIN:VEVENT SUMMARY:Miguel Zumalacarregui (Max Planck Institute for Gravitational Phy sics) DTSTART:20260126T050000Z DTEND:20260126T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/100 DESCRIPTION:Title: A magnified and diffracted black hole merger (GW231123)\nby M iguel Zumalacarregui (Max Planck Institute for Gravitational Physics) as part of Cosmology Talks\n\n\nAbstract\nCan gravitational waves get gravita tionally lensed? The first ever detection of this might have just happened . This is especially cool because if we could routinely measure lensing of gravitational waves\, we could use that to measure all sorts of other imp ortant things like the Hubble constant and precision tests of gravity to n ame just two. One of the interesting things you will hear about in today's talk is an improved modeling of the candidate lens. This better nails dow n the probability that the wave really was lensed and even more fun gives insight into what astrophysical things the source and lens could be. In to day's talk\, we're joined by Miguel Zumalacarregui from the Max Plank Inst itute for Gravitational Physics in Potsdam\, Germany his new paper.\n\nVid eo recording: youtub e.com/watch?v=ZGqOpDTL8k4\n\nMiguel: miguelzuma.github.io\n\nPaper: arXiv: 2512.17631\n\nLigo-Virgo-Kagra analysis: arXiv: 2512.16347\n\n
\n\nIn dex to Key Parts of the Talk\n\n[0:00:00] Shaun's intro\; potential new way to m easure H0 and test gravity
\n\n[0:00:54] Miguel's overview on paper and some thin gs it now allows doing
\n\n[0:02:25] Quick intro to the results\; statistical an alysis supports the lensing hypothesis\; non-symmetric lens
\n\n[0:05:26] Is the re anything confusing about these results?
\n\n[0:06:26] Background and motivati on for this research
\n\n[0:11:15] Why lensing analysis can be done with gravita tional waves
\n\n[0:13:05] Error bars on the parameters
\n\n[0:14:17] Journey of a len sed gravitational wave
\n\n[0:19:22] Predicting and extracting these signals\; Wave-optics lensing
\n\n[0:21:58] Frequency evolution
\n\n[0:26:39] How different is a lensed one from unlensed one with different mass?
\n\n[0:27:17] Lens model\; Point lens + external potential
\n\n[0:34:22] GW231123 Bayesian analysis\; 3 m odels
\n\n[0:41:04] Caveat: bias factors
\n\n[0:48:07] Resolution of unlensed analys is inconsistencies between different models
\n\n[0:51:02] Surprising feature: s ky localization is much wider for the lensing analysis
\n\n[0:54:47] Microlens properties
\n\n[0:58:03] What is the microlens? (IMBH\, stellar cluster\, DM ob ject\, etc?)
\n\n[1:02:44] Additional macro-images?
\n\n[1:05:51] Where to next? Out look: Additional lensing signatures
\n\n[1:10:17] Outlook: discover sources bey ond the detector horizon
\n\n[1:11:27] Another twist: lensing multi-messenger d elections
\n\n[1:12:46] Conclusions
\n\n[1:14:04] Particularly interesting cosmology work that's underappreciated by the community
\n LOCATION:https://researchseminars.org/talk/CosmologyTalks/100/ END:VEVENT BEGIN:VEVENT SUMMARY:Jessie Muir\, Juan Mena-Fernández\, Santiago Avila\, Maria Vincen zi (Dark Energy Survey Collaboration) DTSTART:20260204T050000Z DTEND:20260204T060000Z DTSTAMP:20260422T225706Z UID:CosmologyTalks/101 DESCRIPTION:Title: Dark Energy Survey - Combined cosmology from BAO + SN (+CMB)\ nby Jessie Muir\, Juan Mena-Fernández\, Santiago Avila\, Maria Vincenzi ( Dark Energy Survey Collaboration) as part of Cosmology Talks\n\n\nAbstract \nFour members of the Dark Energy Survey Collaboration discuss the latest findings. This talk is based on these two papers on the arXiv:\n\n(1) Main talk content: [2503.06712] Dar k Energy Survey: implications for cosmological expansion models from the f inal DES Baryon Acoustic Oscillation and Supernova data\n\n(2) Newly r eleased paper: [2601.14864] Dar k Energy Survey: DESI-Independent Angular BAO Measurement\n\nAbout the authors: Jessie Muir\, Juan Mena-Fernández\, Santiago Avila\, Maria Vincenzi\n\n
\n\nIndex to Key Parts of the Talk\n\n[0:00:00] Shaun's intro\n\n[0:01:16] Overview of findings\n\n[0:02:40] How independent is this from DESI?\n\n[0:03:38] Anything particularly sur prising from the analysis?\n\n[0:04:15] Tensions in simpler models\, data reconciled with w0waCDM< /a>\n\n[0:08:40] SN Ia and B AO as distance probes\n\n[0:10:17] The Dark Energy Survey (photometric)\n\n[0:11:43] 4 probes: SN Ia\, BAO\, WL + GC\, GC counts\n\n[0:12:25] 2024 : Λ's annus horribilis\n\n[0:15:08] The DES SN Y5 sample\n\n[0:19:15] DES SN Systematics\n\n[0:22:37] DES Y6 BAO\n\n[0:30:58] Galaxy clustering: BAO signal\n\n[0:35:32] Combining SN and BAO : expansion history model\n\n[0:38:11] DES BAO + SN + ΛCDM + θₛ: tensions\n\n[0:41:00] Curvature: kΛCDM\n\n[0:45:25] DES expansion models: wCDM and w0waCDM\n\n[0 :54:24] Hubble tension is not resolved\n\n[1:02:38] Results in νΛCDM\n\n[1:06:07] Where to next? Future of DES\n\n [1:07:50] Future of BAO \n\n[1:09:22] Future of SN< /a>\n\n[1:12:55] What curre nt cosmology work is underappreciated by the community?\n\n[1:13:40] Impact of DES SN-Dovekie \n LOCATION:https://researchseminars.org/talk/CosmologyTalks/101/ END:VEVENT END:VCALENDAR