BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Gordon Semenoff (University of British Columbia) DTSTART:20200612T163000Z DTEND:20200612T173000Z DTSTAMP:20260422T212749Z UID:CMU-TP/1 DESCRIPTION:Title: E ntanglement and the Infrared\nby Gordon Semenoff (University of Britis h Columbia) as part of Carnegie Mellon theoretical physics\n\nAbstract: TB A\n LOCATION:https://researchseminars.org/talk/CMU-TP/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Angelo Esposito (EPFL) DTSTART:20200619T163000Z DTEND:20200619T173000Z DTSTAMP:20260422T212749Z UID:CMU-TP/2 DESCRIPTION:Title: A n effective field theory for acoustic and pseudo-acoustic phonons in solid s\nby Angelo Esposito (EPFL) as part of Carnegie Mellon theoretical ph ysics\n\n\nAbstract\nSolids generally feature many phonon branches\, with different dispersion relations. Gapless acoustic phonons are known to be t he Goldstone bosons of the spontaneous breaking of spacetime symmetries as sociated to the solid phase. Other gapped phonons are generally non-univer sal degrees of freedom\, which depend on the microscopic details of the so lid. In this talk I will show that some of these gapped phonons can actual ly be seen as pseudo-Goldstones associated to some small explicit breaking . In this regime it is possible to include them in a low-energy EFT\, toge ther with the gapless phonons. I will explicitly construct such an EFT for the case of one and two spatial dimensions\, two ‘flavors’ and in the isotropic limit. I will then compute some test observables and show that they match what already known (when available).\n LOCATION:https://researchseminars.org/talk/CMU-TP/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Luca Delacretaz (University of Chicago) DTSTART:20200710T163000Z DTEND:20200710T173000Z DTSTAMP:20260422T212749Z UID:CMU-TP/3 DESCRIPTION:Title: H eavy operators and hydrodynamic tails\nby Luca Delacretaz (University of Chicago) as part of Carnegie Mellon theoretical physics\n\n\nAbstract\n The late time physics of interacting QFTs at finite temperature is control led by hydrodynamics. For CFTs this implies that heavy operators -- which are generically expected to create thermal states -- can be studied semicl assically. We show that hydrodynamics universally fixes the OPE coefficien ts C_{HH'L}\, on average\, of all neutral light operators with two non-ide ntical heavy ones\, as a function of the scaling dimension and spin of the operators. These methods can be straightforwardly extended to CFTs with g lobal symmetries\, and generalize recent EFT results on large charge opera tors away from the case of minimal dimension at fixed charge. We also revi sit certain aspects of late time thermal correlators in QFT and other diff usive systems.\n LOCATION:https://researchseminars.org/talk/CMU-TP/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Graham White (TRIUMF) DTSTART:20200724T160000Z DTEND:20200724T173000Z DTSTAMP:20260422T212749Z UID:CMU-TP/4 DESCRIPTION:Title: B BN and CMB bounds on hidden sector vectors\nby Graham White (TRIUMF) a s part of Carnegie Mellon theoretical physics\n\n\nAbstract\nNew dark vect or bosons that couple very feebly to regular matter can be produced\nin th e early universe and decay after the onset of Big Bang Nucleosynthesis (BB N)\nor the formation of the cosmic microwave background (CMB) at recombina tion. The\nenergy injected by such decays can modify the light element abu ndances or modify\nthe power and frequency spectra of the CMB. In this wor k we study the constraints\nimplied by these considerations on a range of sub-GeV dark vectors including the\nkinetically mixed dark photon\, as wel l as gauge B-L and lepton families. We focus on the \neffects of electroma gnetic energy injection\, and we update\nprevious investigations of the da rk photon by taking into account non-universality\nin the photon cascade s pectrum relevant for BBN and the energy dependence of the\nionization effi ciency after recombination in our treatment of modifications to the CMB.\n LOCATION:https://researchseminars.org/talk/CMU-TP/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Nabil Iqbal (Durham University) DTSTART:20200807T160000Z DTEND:20200807T173000Z DTSTAMP:20260422T212749Z UID:CMU-TP/5 DESCRIPTION:Title: F rom generalized global symmetries to pulsar magnetospheres\nby Nabil I qbal (Durham University) as part of Carnegie Mellon theoretical physics\n\ n\nAbstract\nCertain quantum field theories possess generalized global sym metries\; just as ordinary global symmetries enforce the conversation of p article number\, generalized global symmetries enforce the conservation of extended objects\, such as strings. I will review this symmetry principle and argue that it governs the long-distance physics of conventional 4d el ectromagnetism\, where the strings in question are magnetic field lines. I will then apply it to construct a novel effective theory for the descript ion of strongly magnetized plasmas. One potential application of this new effective theory is to astrophysical pulsars\, which are thought to be sur rounded by strong magnetic fields as well as a high density of charged par ticles\; the resulting zero temperature system is highly nonlinear. At lea ding order in derivatives our new effective theory agrees with the standar d treatment in terms of ``force-free electrodynamics''. The inclusion of h igher derivative terms however generically results in new and potentially observationally relevant effects\, such as electric fields that accelerate charges to high energies along magnetic field lines.\n LOCATION:https://researchseminars.org/talk/CMU-TP/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Michael Landry (Columbia University) DTSTART:20200717T150000Z DTEND:20200717T160000Z DTSTAMP:20260422T212749Z UID:CMU-TP/6 DESCRIPTION:Title: T he coset construction for non-equilibrium systems\nby Michael Landry ( Columbia University) as part of Carnegie Mellon theoretical physics\n\n\nA bstract\nWe propose a systematic coset construction of non-equilibrium eff ective field theories (EFTs) governing the long-distance and late-time dy namics of relativistic\, finite-temperature condensed matter systems. Our non-equilibrium coset construction makes significant advances beyond more standard coset constructions in that it takes advantage of recently-devel oped techniques\, which allow the formulation of non-equilibrium effectiv e actions that account for quantum and thermal fluctuations as well as di ssipation. Because these systems exist at finite temperature\, the EFTs li ve on the closed-time-path of the Schwinger-Keldysh contour. To demonstrat e the legitimacy of this coset construction\, we successfully reproduce th e known EFTs for fluids and superfluids at finite temperature. Then\, (tim e permitting) to demonstrate its utility\, we construct novel EFTs for sol ids\, supersolids\, and four phases of liquid crystals\, all at finite tem perature. We thereby combine the non-equilibrium effective action and the coset construction to create a powerful tool that can be used to study ma ny-body systems out of thermal equilibrium.\n LOCATION:https://researchseminars.org/talk/CMU-TP/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Carl Rodriguez (Carnegie Mellon University) DTSTART:20200731T160000Z DTEND:20200731T163000Z DTSTAMP:20260422T212749Z UID:CMU-TP/7 DESCRIPTION:Title: M odeling Dense Star Clusters and the gravitational waves they create\nb y Carl Rodriguez (Carnegie Mellon University) as part of Carnegie Mellon t heoretical physics\n\n\nAbstract\nThe lives of massive star clusters are i nevitably linked to the assembly and evolution of the galaxies they inhabi t. While significant progress has been made over the past several decades at separately modeling both galaxy formation and the dynamics of collision al star clusters\, the connection between the two remains poorly understoo d. In this talk\, I will describe how we model dense star clusters\, both analytically and numerically\, and what motivates our typical choices of i nitial conditions. I will then describe a recent project to model clusters self-consistently from collapsing giant molecular clouds in an MHD simula tion of a Milky Way-sized galaxy. Finally\, I will connect these results t o the binary black holes formed by isolated binaries and dense star cluste rs\, including GW190412\, a recently announced binary merger with unique m asses and spins.\n LOCATION:https://researchseminars.org/talk/CMU-TP/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Andrey Gromov (Brown University) DTSTART:20201030T170000Z DTEND:20201030T180000Z DTSTAMP:20260422T212749Z UID:CMU-TP/8 DESCRIPTION:Title: F ractons and vortices\nby Andrey Gromov (Brown University) as part of C arnegie Mellon theoretical physics\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CMU-TP/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Jyoti Katoch (Carnegie Mellon University) DTSTART:20201002T170000Z DTEND:20201002T180000Z DTSTAMP:20260422T212749Z UID:CMU-TP/9 DESCRIPTION:Title: P robing two-dimensional materials using focused angle-resolved photoemissio n spectroscopy\nby Jyoti Katoch (Carnegie Mellon University) as part o f Carnegie Mellon theoretical physics\n\n\nAbstract\nTwo-dimensional (2D) materials offer the freedom to create novel condensed matter systems\, wit h unique properties\, by mechanically assembling different (or same) 2D ma terials layer-by-layer to form atomically sharp vertical or lateral hetero structures. The van der Waals (vdW) heterostructures with small lattice mi smatch and a relatively small twist angle between the constituent layers\, have shown to exhibit coexisting complex phases of matter including Mott insulating state\, superconductivity\, bound quasiparticles\, and topologi cal states. In addition\, the extreme surface sensitivity of two-dimension al (2D) materials provides an unprecedented opportunity to engineer the ph ysical properties of these materials using external perturbations. In this talk\, I will discuss the utilization of angle-resolved photoemission spe ctroscopy (ARPES) with high spatial resolution to investigate the electron ic band structure of 2D heterostructures and their devices. This can shed light on the intricate relationship between controlled external perturbati ons\, substrate\, and electronic properties of 2D materials [1\, 2]. In pa rticular\, I will discuss our in-operando nanoARPES results that exhibit h ighly tunable many-body effects in graphene devices [3] and tunable van Ho ve singularities in twisted bilayer graphene [4]. \n\nReferences:\n[1] Kat och et. al.\, Nature Physics 14\, 355-359 (2018).\n[2] Ulstrup\, et. al.\, Science Advances\, Vol. 6\, no. 14\, eaay6104\, (2020).\n[3] Muzzio\, et. al.\, Physical review B Rapid Communications 101\, 201409(R) (2020).\n[4] Jones\, et. al.\, Adv. Mater. 2020\, 32\, 2001656.\n LOCATION:https://researchseminars.org/talk/CMU-TP/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Michael Pretko (University of Colorado) DTSTART:20200814T160000Z DTEND:20200814T173000Z DTSTAMP:20260422T212749Z UID:CMU-TP/10 DESCRIPTION:Title: Fractons: A New Type of Particle\nby Michael Pretko (University of Col orado) as part of Carnegie Mellon theoretical physics\n\n\nAbstract\nA fra cton is an unusual new type of emergent quasiparticle found in various con densed matter systems. Fractons are characterized by a set of mobility re strictions\, which force isolated fractons to be strictly immobile\, while certain bound states of fractons remain free to move. This behavior lead s to a variety of unusual phenomenology\, such as non-ergodic and gravitat ional behavior\, and may lead to advances in quantum memory storage. In t his talk\, I will give a broad overview of the field of fractons\, includi ng both introductory material and recent advances. I will describe the ba sics of the theoretical formalism for fractons in terms of tensor gauge th eories and higher moment conservation laws. I will then discuss various p hysical realizations of fractons\, such as spin models and topological lat tice defects\, along with the unusual phenomenology exhibited by fractons. I will conclude by outlining some open questions in the field.\n LOCATION:https://researchseminars.org/talk/CMU-TP/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Tim Cohen (University of Oregon) DTSTART:20201009T170000Z DTEND:20201009T180000Z DTSTAMP:20260422T212749Z UID:CMU-TP/11 DESCRIPTION:Title: Soft de Sitter Effective Theory\nby Tim Cohen (University of Oregon) a s part of Carnegie Mellon theoretical physics\n\n\nAbstract\nIn this talk\ , I will introduce the Soft de Sitter Effective Theory (SdSET)\, whose pur pose is to model the long wavelength dynamics of quantum fluctuations beyo nd the horizon. After providing some conceptual and technical issues that motivate the need for a new EFT approach\, I will explain how we identify the propagating low energy degrees of freedom\, along with their scaling under a power counting scheme and their transformation properties under th e symmetries that persist to the IR. I will sketch how to derive the SdSE T action\, and will argue that it can be expressed as an expansion in loca l operators\, augmented by stochastic initial conditions. Finally\, I wil l show how this framework can be applied to a number of physically interes ting problems: massive scalar fields in dS\, light scalar fields and stoch astic inflation\, conservation of the inflationary adiabatic modes\, and t he phase transition to eternal inflation.\n LOCATION:https://researchseminars.org/talk/CMU-TP/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Claudia de Rham (Imperial College) DTSTART:20200918T170000Z DTEND:20200918T180000Z DTSTAMP:20260422T212749Z UID:CMU-TP/12 DESCRIPTION:Title: Causality and Positivity with Gravity\nby Claudia de Rham (Imperial Co llege) as part of Carnegie Mellon theoretical physics\n\n\nAbstract\nI wil l investigate the propagation of gravitational waves on curved spacetimes within the low energy effective field theory of gravity\, where effects fr om heavy fields are captured by higher dimensional curvature operators. De pending on the spin of the particles integrated out\, the speed of gravita tional waves at low energy can be either superluminal or subluminal as com pared to the causal structure observed by other species. I will clarify wh y a mild level of superluminality is not in contradiction with causality\, analyticity or Lorentz invariance and show how consistent gravitational l ow energy effective theories can self-protect by ensuring that any time ad vance and superluminality calculated within the regime of validity of the effective theory is necessarily unresolvable for such theories. These cons iderations are particularly relevant for putting constraints on cosmologic al and gravitational effective field theories and I will provide explicit criteria to be satisfied so as to ensure causality.\n LOCATION:https://researchseminars.org/talk/CMU-TP/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Alexandre Le Tiec (Observatoire de Paris) DTSTART:20200925T170000Z DTEND:20200925T180000Z DTSTAMP:20260422T212749Z UID:CMU-TP/14 DESCRIPTION:Title: Tidal Love numbers of Kerr black holes\nby Alexandre Le Tiec (Observat oire de Paris) as part of Carnegie Mellon theoretical physics\n\n\nAbstrac t\nThe open question of whether a black hole can become tidally deformed b y an external gravitational field has profound implications for fundamenta l physics\, astrophysics and gravitational-wave astronomy. Love numbers ch aracterize the tidal deformability of compact objects such as astrophysica l (Kerr) black holes. We prove that all Love numbers vanish identically fo r a Kerr black hole in the nonspinning limit or for an axisymmetric tidal perturbation. In contrast to this result\, we show that Love numbers are g enerically nonzero for a spinning black hole. Specifically\, to linear ord er in the black hole spin and the weak perturbing tidal field\, we compute in closed form the Love numbers that couple the mass-type and current-typ e quadrupole moments to the electric-type and magnetic-type quadrupolar ti dal fields. This tidal deformability is potentially observationally import ant through its contribution to the accumulated gravitational-wave phase o f an inspiralling stellar-mass compact object into a massive black hole. W e show that for a dimensionless black hole spin ~ 0.1\, the nonvanishing q uadrupolar Love numbers are ~ 0.002. This indicates that\, despite black h oles being particularly "rigid" compact objects\, their nonvanishing tidal deformability could be detected by the future gravitational-wave interfer ometer LISA.\n LOCATION:https://researchseminars.org/talk/CMU-TP/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Eric Poisson (University of Guelph) DTSTART:20201016T170000Z DTEND:20201016T180000Z DTSTAMP:20260422T212749Z UID:CMU-TP/15 DESCRIPTION:Title: Love tensor of a slowly rotating body\nby Eric Poisson (University of Guelph) as part of Carnegie Mellon theoretical physics\n\n\nAbstract\nA ro tating body immersed in a gravitomagnetic tidal field is subjected to a Lo rentz-like force $v \\times B$\, where $v$ is the rotational velocity\, an d $B$ is the gravitomagnetic field\, which is produced by mass currents as sociated with the companion’s orbital motion. The body’s response to t his force can be described in terms of a tidal polarizability. In this tal k I describe a post-Newtonian theory of this tidal polarizability\, which takes the form of a Love tensor\, a four-index object that relates the bod y's current quadrupole moment $S_{jk}$ to the gravitomagnetic tidal moment $B_{jk}$. The tensorial nature of this quantity has to do with the fact t hat each $e^{i m \\phi}$ piece of the tidal force gives rise to an m-speci fic velocity perturbation\, and therefore to a tidal polarizability that d epends on m. The collection of these m-specific Love numbers makes up the Love tensor.\n LOCATION:https://researchseminars.org/talk/CMU-TP/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Pavel Kovtun (University of Victoria) DTSTART:20201023T170000Z DTEND:20201023T180000Z DTSTAMP:20260422T212749Z UID:CMU-TP/16 DESCRIPTION:Title: Pushing the limits of hydrodynamics\nby Pavel Kovtun (University of Vi ctoria) as part of Carnegie Mellon theoretical physics\n\n\nAbstract\nHydr odynamics is a well-established field with a venerable history. In this ta lk\, I will focus on foundational aspect of hydrodynamics which came to li ght in recent years. Do the equations of hydrodynamics even make sense? To what degree can the crudeness of hydrodynamics be improved? What about th e phenomena that hydrodynamics should describe but fails to? And how unive rsal is it really?\n LOCATION:https://researchseminars.org/talk/CMU-TP/16/ END:VEVENT BEGIN:VEVENT SUMMARY:Jim Halverson (Northeastern University) DTSTART:20200904T133000Z DTEND:20200904T143000Z DTSTAMP:20260422T212749Z UID:CMU-TP/17 DESCRIPTION:Title: Neural Networks and Quantum Field Theory\nby Jim Halverson (Northeaste rn University) as part of Carnegie Mellon theoretical physics\n\n\nAbstrac t\nWe propose a theoretical understanding of neural networks in terms of W ilsonian effective field theory. The correspondence relies on the fact tha t many asymptotic neural networks are drawn from Gaussian processes\, the analog of non-interacting field theories. Moving away from the asymptotic limit yields a non-Gaussian process and corresponds to turning on particle interactions\, allowing for the computation of correlation functions of n eural network outputs with Feynman diagrams. Minimal non-Gaussian process likelihoods are determined by the most relevant non-Gaussian terms\, accor ding to the flow in their coefficients induced by the Wilsonian renormaliz ation group. This yields a direct connection between overparameterization and simplicity of neural network likelihoods. Whether the coefficients are constants or functions may be understood in terms of GP limit symmetries\ , as expected from 't Hooft's technical naturalness. General theoretical c alculations are matched to neural network experiments in the simplest clas s of models allowing the correspondence. Our formalism is valid for any of the many architectures that becomes a GP in an asymptotic limit\, a prope rty preserved under certain types of training.\n LOCATION:https://researchseminars.org/talk/CMU-TP/17/ END:VEVENT BEGIN:VEVENT SUMMARY:Tina Kahniashvili (Carnegie Mellon University) DTSTART:20201104T170000Z DTEND:20201104T180000Z DTSTAMP:20260422T212749Z UID:CMU-TP/18 DESCRIPTION:Title: Circular polarization of gravitational waves from the early-universe turbu lent sources\nby Tina Kahniashvili (Carnegie Mellon University) as par t of Carnegie Mellon theoretical physics\n\n\nAbstract\nI will present dir ect numerical simulations to compute the net circular polarization of grav itational waves from helical (chiral) turbulent sources in the early unive rse for a variety of initial conditions. I will discuss the resulting grav itational wave signal assuming different turbulence genesis such as magne tically or kinetically dominant cases. Under realistic physical conditions in the early universe we have computed numerically for the first time the total (integrated over all wavenumbers) polarization degree of the gravit ational waves and its spectral distribution. Our major finding consists of the spectral polarization degree that strongly depends on the initial con ditions. The peak of the spectral polarization degree occurs (in the waven umber space) at twice the typical wavenumber \nof the source\, as expected \, and for the fully helical decaying turbulence\, reaches its maximum (10 0\\%) only at the peak. In addition\, we have determined the temporal evol ution of the turbulent sources as well as the resulting gravitational wave s\, showing that the dominant contribution to the spectral energy density happens shortly after the source activation and through artificially prolo nged (slow decay) turbulence the increase of the gravitational wave amplit ude at low frequencies can be achieved. Finally\, I will address the detec tion prospects for the net polarization arguing that its detection contain s clean information (including the generation mechanisms\, time\, and stre ngth) about the sources of possible parity violations in the early univers e.\n LOCATION:https://researchseminars.org/talk/CMU-TP/18/ END:VEVENT BEGIN:VEVENT SUMMARY:Tanguy Grall (DAMTP\, University of Cambridge) DTSTART:20201204T180000Z DTEND:20201204T190000Z DTSTAMP:20260422T212749Z UID:CMU-TP/19 DESCRIPTION:Title: Symmetries and unitarity of theories with spontaneously broken boosts\ nby Tanguy Grall (DAMTP\, University of Cambridge) as part of Carnegie Mel lon theoretical physics\n\n\nAbstract\nSystems with spontaneously broken L orentz boosts are found everywhere in nature\, from condensed matter to th e early universe. In this talk I will discuss Effective Field Theories (EF Ts) of a single\, shift-symmetric\, phonon that parametrises the breaking of time translations and Lorentz boosts. Such theories include for instanc e scalar modes in the EFT of inflation\, superfluid or galileid phonons (t he broken phase of Galileon scalar EFTs).\n\nIn the first part\, I will pr esent an algebraic classification of such theories\, based on their non-li nearly realised symmetries\, in direct analogy with previous classificatio ns of so-called Exceptional (Lorentz invariant) EFTs. In doing so I will p resent\, for instance\, a new galileid theory\, “the extended galileid ”\, as well as other better known superfluid and galileid theories.\n\nI n the second part\, I will discuss perturbative unitarity of such theories \, making use of the unbroken symmetries of 2-to-2 scattering amplitudes. A common feature of non-Lorentz invariant EFTs is that they have a cut-off not only in energy but also in momentum. I will show how this arises in o ur EFTs and derive partial-wave bounds that can be used to probe their str ong coupling regime. As a practical application\, I will discuss the impli cations of these results on the EFT of inflation in the sub-horizon region .\n LOCATION:https://researchseminars.org/talk/CMU-TP/19/ END:VEVENT BEGIN:VEVENT SUMMARY:Jingping Li (Yale University) DTSTART:20201113T180000Z DTEND:20201113T190000Z DTSTAMP:20260422T212749Z UID:CMU-TP/20 DESCRIPTION:Title: Gravitational Radiation from the Double Copy\nby Jingping Li (Yale Uni versity) as part of Carnegie Mellon theoretical physics\n\n\nAbstract\nWe show that the perturbative radiative solutions to the classical Yang-Mills equations from the scattering of spinning particle sources exhibit color- kinematic duality\, a duality originally discovered in the context of pert urbative tree-level scattering amplitudes of Yang-Mills theory. This enabl es a classical double-copy construction that generates corresponding class ical solutions in string gravity (axion-dilaton gravity). While the origin al double copy of scattering amplitudes traces back to results in perturba tive string theories\, we find that classical open and closed strings are possible “UV completions” to these worldline effective field theories of the sources by comparing to the low energy radiation from these rotatin g strings. Moreover\, we show that the higher dimensional operators encodi ng tidal deformation can also be added to this construction\, provided tha t the Wilson coefficients of the dilatonic and axionic operators are fixed with respect to the gravitational ones.\n LOCATION:https://researchseminars.org/talk/CMU-TP/20/ END:VEVENT BEGIN:VEVENT SUMMARY:Vicharit Yingcharoenrat (SISSA) DTSTART:20201209T170000Z DTEND:20201209T180000Z DTSTAMP:20260422T212749Z UID:CMU-TP/21 DESCRIPTION:Title: Beyond perturbation theory in inflation\nby Vicharit Yingcharoenrat (S ISSA) as part of Carnegie Mellon theoretical physics\n\n\nAbstract\nIn thi s talk I will first discuss a motivation why one needs to go beyond pertur bation theory (PT) in inflation as going to the tail of the distribution o f the primordial fluctuations. Then I will propose that the way to go beyo nd PT is equivalent to performing a calculation in the semi-classical limi t. As an analogy\, I will show a simple calculation of the ground-state wa vefunction in the semi-classical limit for a quantum mechanical system. Af ter that\, I will move to a toy model of inflation which for simplicity in volves only derivative couplings. As a result\, the wavefunction of the Un iverse in this semi-classical limit exhibits a non-perturbative behaviour for large coupling limit.\n LOCATION:https://researchseminars.org/talk/CMU-TP/21/ END:VEVENT BEGIN:VEVENT SUMMARY:Enrico Pajer (Cambridge University) DTSTART:20210407T160000Z DTEND:20210407T170000Z DTSTAMP:20260422T212749Z UID:CMU-TP/22 DESCRIPTION:Title: A timeless History of Time\nby Enrico Pajer (Cambridge University) as part of Carnegie Mellon theoretical physics\n\n\nAbstract\nWe have overwhe lming evidence that the distribution of everything on very large scales is of primorial origin. According to the leading paradigm of inflation\, the statistics of these primordial perturbations can be traced back to correl ators of quantum fields on a curved quasi-de Sitter spacetime. This gives us the unique opportunity to probe the fundamental laws of physics at very high energies as well as the perturbative regime of quantum gravity.\nUnf ortunately\, due to the creativity of theorists and the paucity of data ab out the primordial universe\, there is a huge number of models compatible with all measurements\, featuring a wide variety of mechanisms\, symmetrie s\, and spectra of particles.The reason can be traced back to the fact tha t we don't observe the time evolution during inflation\, but only its fina l outcome.\nIn this talk I will report on the recent progress in developin g a completely new "bootstrap" approach to derive predictions from the ver y early universe that make no reference to time and the un-observable time evolution. The bootstrap approach builds directly upon the fundamental pi llars of physics\, namely unitarity\, locality and symmetries and is highl y model independent. I will show how these principles can be used to deriv e many classical and new inflationary predictions associated with primordi al non-Gaussianity in a way that is both computationally simpler and conce ptually more transparent.\n LOCATION:https://researchseminars.org/talk/CMU-TP/22/ END:VEVENT BEGIN:VEVENT SUMMARY:Ratindranath Akhoury (University of Michigan) DTSTART:20210210T170000Z DTEND:20210210T180000Z DTSTAMP:20260422T212749Z UID:CMU-TP/23 DESCRIPTION:Title: Entanglement\, renormalization and effective field theories\nby Ratind ranath Akhoury (University of Michigan) as part of Carnegie Mellon theoret ical physics\n\n\nAbstract\nWe develop the idea that renormalization\, dec oupling of heavy particle effects from low energy physics and the construc tion of effective field theories are intimately linked to the momentum spa ce entanglement of disparate modes of an interacting quantum field theory. Using unitary transformations to decouple these modes at the perturbative level\, we show in a scalar field theoretical model with light and heavy fields\, how renormalization may be consistently implemented and how the l ow energy effective field theory can be constructed. We also obtain a reno rmalization group equation in this framework and apply it to the scalar fi eld theoretical model.\n LOCATION:https://researchseminars.org/talk/CMU-TP/23/ END:VEVENT BEGIN:VEVENT SUMMARY:Csaba Csaki (Cornell University) DTSTART:20210217T170000Z DTEND:20210217T180000Z DTSTAMP:20260422T212749Z UID:CMU-TP/24 DESCRIPTION:Title: Magnetic scattering: pairwise little group and pairwise helicity\nby C saba Csaki (Cornell University) as part of Carnegie Mellon theoretical phy sics\n\n\nAbstract\nI discuss how to construct a Lorentz-invariant S-matri x for the scattering of electrically and magnetically charged particles. A key ingredient is a revision of our fundamental understanding of multi-pa rticle representations of the Poincaré group. Surprisingly\, the asymptot ic states for electric-magnetic scattering transform with an additional li ttle group phase\, associated with pairs of electrically and magnetically charged particles. I will discuss the general construction of such states. The resulting "pairwise helicity" is identified with the quantized "cross product" of charges e1 g2- e2 g1 for every charge-monopole pair\, and re presents the extra angular momentum stored in the asymptotic electromagnet ic field. We define a new kind of pairwise spinor-helicity variable\, whic h serves as an additional building block for electric-magnetic scattering amplitudes. We then construct the most general 3-point S-matrix elements\, as well as the full partial wave decomposition for the 2 -> 2 fermion-mon opole S-matrix. In particular\, we derive the famous helicity flip in the lowest partial wave as a simple consequence of a generalized spin-helicity selection rule\, as well as the full angular dependence for the higher pa rtial waves. Our construction provides a significant new achievement for t he on-shell program\, succeeding where the Lagrangian description has so f ar failed.\n LOCATION:https://researchseminars.org/talk/CMU-TP/24/ END:VEVENT BEGIN:VEVENT SUMMARY:Christopher White (Queen Mary University) DTSTART:20210303T170000Z DTEND:20210303T180000Z DTSTAMP:20260422T212749Z UID:CMU-TP/25 DESCRIPTION:Title: The classical double copy from twistor space\nby Christopher White (Qu een Mary University) as part of Carnegie Mellon theoretical physics\n\n\nA bstract\nThe "double copy” is an intriguing and recently discovered rela tionship between quantities in gauge theories and gravity. It has been app lied to (quantum) scattering amplitudes as well as classical solutions\, i ncluding those relevant for gravitational wave experiments. In some cases\ , we can even relate exact solutions in different theories\, although why this works has remained mysterious. In this talk\, I will show that certai n exact double copies can be derived using well-established ideas from twi stor theory\, which also proves that they are more general than previously thought. No previous knowledge of twistors will be assumed.\n LOCATION:https://researchseminars.org/talk/CMU-TP/25/ END:VEVENT BEGIN:VEVENT SUMMARY:Sean Carroll (Caltech) DTSTART:20210203T170000Z DTEND:20210203T180000Z DTSTAMP:20260422T212749Z UID:CMU-TP/26 DESCRIPTION:Title: Extracting the Universe from the Wave Function\nby Sean Carroll (Calte ch) as part of Carnegie Mellon theoretical physics\n\n\nAbstract\nQuantum mechanics is a theory of wave functions in Hilbert space. Many features th at we generally take for granted when we use quantum mechanics -- classica l spacetime\, locality\, the system/environment split\, collapse/branching \, preferred observables\, the Born rule for probabilities -- should in pr inciple be derivable from the basic ingredients of the quantum state and t he Hamiltonian. I will discuss recent progress on these problems\, includi ng consequences for cosmology and quantum gravity.\n LOCATION:https://researchseminars.org/talk/CMU-TP/26/ END:VEVENT BEGIN:VEVENT SUMMARY:Riccardo Rattazzi (EPFL) DTSTART:20210428T153000Z DTEND:20210428T163000Z DTSTAMP:20260422T212749Z UID:CMU-TP/27 DESCRIPTION:Title: The quantum mechanics of a perfect fluid\nby Riccardo Rattazzi (EPFL) as part of Carnegie Mellon theoretical physics\n\n\nAbstract\nFinite densi ty systems can be described by effective field theories with non-linearly realized space-time symmetries\,\nwhose construction resembles that of the QCD chiral lagrangian. Also based on that similarity\, one would expect t he\nconstruction to work equally well classically and quantum mechanically . While that is true for superfluids and solids\,\none instead finds that for genuine fluids things are made more complicated by the unusual dynamic s of their transverse\nmodes\, which are not described by a Fock space. F ocussing on the incompressible limit in 2+1 dimensions\, I illustrate how a consistent quantum mechanical description of a perfect fluid can be obta ined by using the known equivalence between the area preserving diffeomorf ism group in 2D and $SU(N)$ with $N\\to \\infty$.\n LOCATION:https://researchseminars.org/talk/CMU-TP/27/ END:VEVENT BEGIN:VEVENT SUMMARY:Ethan Lake (MIT) DTSTART:20210224T170000Z DTEND:20210224T180000Z DTSTAMP:20260422T212749Z UID:CMU-TP/28 DESCRIPTION:Title: Bose-Luttinger liquids\nby Ethan Lake (MIT) as part of Carnegie Mellon theoretical physics\n\n\nAbstract\nIn this talk I will explain the physic s behind a new class of quantum phases of matter known as ``Bose-Luttinger liquids''. A Bose-Luttinger liquid is a phase of matter which in some res pects can be thought of as a metal\, but with charge carriers that are bos ons\, instead of electrons. For condensed matter theorists\, these phases are interesting because they provide easy-to-understand examples of metall ic systems without quasiparticles\, and may help explain some interesting  quantum critical phenomena in certain types of helical magnets. For hig h-energy theorists\, they are interesting because they provide examples of RG fixed points with infinitely many marginal deformations\, which can no netheless be described using the technology of 2d CFT. This talk will be b ased on the preprint arXiv:2101.02197.\n LOCATION:https://researchseminars.org/talk/CMU-TP/28/ END:VEVENT BEGIN:VEVENT SUMMARY:Tomas Brauner (Stavanger University) DTSTART:20210317T160000Z DTEND:20210317T170000Z DTSTAMP:20260422T212749Z UID:CMU-TP/29 DESCRIPTION:Title: Higher-form and higher-group symmetry in mixed superfluids\nby Tomas B rauner (Stavanger University) as part of Carnegie Mellon theoretical physi cs\n\n\nAbstract\nHigher-form symmetries are symmetries that act on extend ed objects. I will give a brief introduction to this concept and show how higher-form symmetries naturally emerge as a consequence of spontaneous br eaking of ordinary (0-form) symmetries. They can therefore be expected to be present in superfluids and generalizations thereof. Furthermore\, when two or more different types of superfluids are mixed\, a more general symm etry structure appears\, usually referred to as a higher group. The presen ce of this mathematical structure reflects the interplay of topological de fects of the various superfluid components.\n LOCATION:https://researchseminars.org/talk/CMU-TP/29/ END:VEVENT BEGIN:VEVENT SUMMARY:Alfredo Guevara Gonzalez (Harvard University) DTSTART:20210310T170000Z DTEND:20210310T180000Z DTSTAMP:20260422T212749Z UID:CMU-TP/30 DESCRIPTION:Title: From QFT amplitudes to wave scattering in Kerr\nby Alfredo Guevara Gon zalez (Harvard University) as part of Carnegie Mellon theoretical physics\ n\n\nAbstract\nIn recent years\, a striking connection between QFT scatter ing amplitudes and classical black hole physics has been developed.In this talk we will consider the scattering of massless waves off a Kerr black h ole. The classical Newman-Penrose amplitudes are found to coincide with ce rtain QFT amplitudes at finite values of the scattering angle\, provided 1 ) a precise classical limit is implemented on the QFT side and 2) the blac k hole background is modelled as an interacting matter particle with spin. The QFT amplitudes describe the $2\\to 2$ tree-level scattering of a heli city-$|h|$ particle with a massive spin-S particle\, where the spin can be taken arbitrarily high. We will finally discuss the application of our re sults to the computation of gravitational radiation in the (bounded) two-b ody problem.\n LOCATION:https://researchseminars.org/talk/CMU-TP/30/ END:VEVENT BEGIN:VEVENT SUMMARY:Sergey Sibiryakov (CERN) DTSTART:20210331T160000Z DTEND:20210331T170000Z DTSTAMP:20260422T212749Z UID:CMU-TP/31 DESCRIPTION:Title: Black hole induced false vacuum decay from first principles\nby Sergey Sibiryakov (CERN) as part of Carnegie Mellon theoretical physics\n\n\nAbs tract\nIt has been proposed that microscopic black holes can catalyze deca y of metastable false vacuum. The calculations of the decay rate existing in the literature make use of the Euclidean time formalism developed for e quilibrium configurations. This is not the case\, however\, for a realisti c black hole formed by gravitational collapse and emitting Hawking radiati on. I will review the motivations to study black hole catalysis of vacuum decay\, propose a general method to calculate the decay rate\, and illustr ate it on a two-dimensional toy model.\n LOCATION:https://researchseminars.org/talk/CMU-TP/31/ END:VEVENT BEGIN:VEVENT SUMMARY:Ioanna Kourkoulou (Columbia University) DTSTART:20210414T160000Z DTEND:20210414T170000Z DTSTAMP:20260422T212749Z UID:CMU-TP/32 DESCRIPTION:Title: Lorentz invariance in Framids as a potential technical analog of the CCP\nby Ioanna Kourkoulou (Columbia University) as part of Carnegie Mellon theoretical physics\n\n\nAbstract\nThe Framid is a hypothetical system who se ground state spontaneously breaks boost symmetry\, however its stress-e nergy tensor retains a Lorentz-invariant expectation value on the ground s tate\, as we verify explicitly to one-loop order. The mechanism enforcing this result is rather obscure\; in fact\, we think this puzzle is an inter esting technical analog of the cosmological constant problem. I will descr ibe our computations that verify the Lorentz invariance of the expectation value in question\, and how these yield the expected result only thanks t o highly nontrivial cancellations\, which are quite mysterious from the lo w-energy effective theory viewpoint.\n LOCATION:https://researchseminars.org/talk/CMU-TP/32/ END:VEVENT BEGIN:VEVENT SUMMARY:Azadeh Maleknejad (CERN) DTSTART:20210421T160000Z DTEND:20210421T170000Z DTSTAMP:20260422T212749Z UID:CMU-TP/33 DESCRIPTION:Title: Is Our Universe the Remnant of Chiral Anomaly in Inflation?\nby Azadeh Maleknejad (CERN) as part of Carnegie Mellon theoretical physics\n\n\nAbs tract\nModern cosmology has been remarkably successful in describing the U niverse from a second after the Big Bang until today. However\, its physic s before that time is still much less certain. It profoundly involves part icle theory beyond the Standard Model to explain long-standing puzzles: th e origin of the observed matter asymmetry\, nature of dark matter\, massiv e neutrinos\, and cosmic inflation. In this talk\, I will explain that a n ew framework based on embedding axion-inflation in left-right symmetric ga uge extensions of the SM can possibly solve and relate these seemingly unr elated mysteries of modern particle physics and cosmology. The baryon asym metry and dark matter today are remnants of a pure quantum effect (chiral anomaly) in inflation which is the source of CP violation in inflation. As a smoking gun\, this setup has robust observable signatures for the GW ba ckground to be probed by future CMB missions and laser interferometer dete ctors.\n LOCATION:https://researchseminars.org/talk/CMU-TP/33/ END:VEVENT BEGIN:VEVENT SUMMARY:Austin Joyce (University of Chicago) DTSTART:20211208T173000Z DTEND:20211208T183000Z DTSTAMP:20260422T212749Z UID:CMU-TP/34 DESCRIPTION:Title: Gravity as a phase of matter\nby Austin Joyce (University of Chicago) as part of Carnegie Mellon theoretical physics\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CMU-TP/34/ END:VEVENT BEGIN:VEVENT SUMMARY:Angelo Esposito (IAS) DTSTART:20210922T163000Z DTEND:20210922T173000Z DTSTAMP:20260422T212749Z UID:CMU-TP/35 DESCRIPTION:Title: Primordial nongaussianities from consistency relations: a proof of princip le\nby Angelo Esposito (IAS) as part of Carnegie Mellon theoretical ph ysics\n\n\nAbstract\nConsistency relations are the cosmological analogues of the soft pion theorem\, connecting the soft limit of certain correlator s to other correlators. Due to their nonperturbative nature\, they remain true also in fully nonlinear regimes (where the standard approach fails)\, and for astrophysically messy observables (like galaxy distributions).\nI n this seminar I will discuss how we can use the consistency relations for large scale structures to determine whether or not inflation was driven b y the dynamics of a single field. I will do that using a suite of N-body s imulations for the matter distributions\, and discuss how to extend this t o a more realistic scenario.\n LOCATION:https://researchseminars.org/talk/CMU-TP/35/ END:VEVENT BEGIN:VEVENT SUMMARY:Benjamin Doyon (King's College) DTSTART:20211020T163000Z DTEND:20211020T173000Z DTSTAMP:20260422T212749Z UID:CMU-TP/36 DESCRIPTION:Title: The hydrodynamics of many-body integrable systems\nby Benjamin Doyon ( King's College) as part of Carnegie Mellon theoretical physics\n\n\nAbstra ct\nHydrodynamics is a powerful theory for the emergent behaviours at larg e scales of space-time in many-body systems. The theory says that only few degrees of freedom are sufficient in order to describe what is observed a t such scales\, and it provides equations for the dynamics of these degree s of freedom. Think of the simple water waves emerging from the motion and interaction of a myriad of water molecules. It is strongly based on the p resence of microscopic conservation laws in the many-body model\, such as conservation of energy\, momentum and mass. But the standard equations of hydrodynamics fail to describe one-dimensional integrable systems\, includ ing the ultracold atomic gases observed in experiments. Integrable systems admit an extensive number of conservation laws\, which must be taken into account in the emergent hydrodynamic theory. Recently this theory\, dubbe d ``generalised hydrodynamics”\, has been developed. In this talk\, I wi ll review fundamental aspects of hydrodynamics and the main idea and equat ions of generalised hydrodynamics. I will discuss recent cold-atom experim ents that confirm the theory\, some of the exact results that can be obtai ned with this formalism such as nonequilibrium steady states and asymptoti c of correlation functions\, and if time permit some mathematically rigoro us results in these directions.\n LOCATION:https://researchseminars.org/talk/CMU-TP/36/ END:VEVENT BEGIN:VEVENT SUMMARY:Matt Lewandowski (Northwestern U.) DTSTART:20211027T163000Z DTEND:20211027T173000Z DTSTAMP:20260422T212749Z UID:CMU-TP/37 DESCRIPTION:Title: Gravitational Causality and the Self-Stress of Photons\nby Matt Lewand owski (Northwestern U.) as part of Carnegie Mellon theoretical physics\n\n \nAbstract\nWe study causality in gravitational systems beyond the classic al limit. Using on-shell methods\, we consider the one-loop corrections f rom charged particles to the photon energy- momentum tensor —the self-st ress— that controls the quantum interaction between two on-shell photons and one off-shell graviton. The self-stress determines in turn the phase shift and time delay in the scattering of photons against a spectator par ticle of any spin in the eikonal regime. We show that the sign of the bet a-function associated to the running gauge coupling is related to the sign of time delay at small impact parameter. Our results show that\, at firs t post-Minkowskian order\, asymptotic causality\, where the time delay exp erienced by any particle must be positive\, is respected quantum mechanica lly. Contrasted with asymptotic causality\, we explore a local notion of causality\, where the time delay is longer than the one of gravitons\, whi ch is seemingly violated by quantum effects.\n LOCATION:https://researchseminars.org/talk/CMU-TP/37/ END:VEVENT BEGIN:VEVENT SUMMARY:Massimiliano-Maria Riva (IPhT) DTSTART:20211201T173000Z DTEND:20211201T183000Z DTSTAMP:20260422T212749Z UID:CMU-TP/39 DESCRIPTION:Title: Gravitational Bremsstrahlung in the Post-Minkowskian expansion\nby Mas similiano-Maria Riva (IPhT) as part of Carnegie Mellon theoretical physics \n\n\nAbstract\nI will discuss the scattering of two compact objects inter acting via gravity\, using the so-called world-line Effective Field Theory approach in the post-Minkowskian expansion (i.e. expanding in the Newton' s constant G but not in the velocities). In particular\, I will focus on t he computation of classical observables such as the total emitted momentum . This is obtained by phase-space integration of the graviton momentum wei ghted by the modulo squared of the radiation amplitude. It can be recast a s an effective cut two-loop integral that I will solve using techniques bo rrowed from particle physics.\n LOCATION:https://researchseminars.org/talk/CMU-TP/39/ END:VEVENT BEGIN:VEVENT SUMMARY:Julio Parra Martinez (Caltech) DTSTART:20211116T173000Z DTEND:20211116T183000Z DTSTAMP:20260422T212749Z UID:CMU-TP/40 DESCRIPTION:Title: Geometric soft theorems (part 1)\nby Julio Parra Martinez (Caltech) as part of Carnegie Mellon theoretical physics\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CMU-TP/40/ END:VEVENT BEGIN:VEVENT SUMMARY:Guanhao Sun (Columbia U.) DTSTART:20211103T163000Z DTEND:20211103T173000Z DTSTAMP:20260422T212749Z UID:CMU-TP/41 DESCRIPTION:Title: Anisotropies in icosahedral inflation\nby Guanhao Sun (Columbia U.) as part of Carnegie Mellon theoretical physics\n\n\nAbstract\nIn this talk\, I will present recent work done on analyzing the unique observational imp rints of icosahedral inflation. Icosahedral inflation is a variation of so lid inflation\, in which the dynamics of the system are driven by a triple t of scalars satisfying internal icosahedral symmetry. This model is motiv ated by a hunt for an intrinsically anisotropic symmetry that gives isotro pic background stress tensor and two-point function\, and the model predic ts a completely isotropic scalar power spectrum while introducing anisotro pic corrections to the tensor power spectrum and the bispectrum. A mixed s calar-tensor two-point function is also allowed. Observationally\, it is p ossible to have a maximally anisotropic scalar bispectrum\, and non-zero T -B and E-B correlations for the CMB temperature-polarization spectrum. The statistical anisotropies also give rise to non-zero bipolar spherical har monics and bipolar power spectrum\, which are calculated and will be discu ssed in the talk.\n LOCATION:https://researchseminars.org/talk/CMU-TP/41/ END:VEVENT BEGIN:VEVENT SUMMARY:Julio Parra Martinez (Caltech) DTSTART:20211117T173000Z DTEND:20211117T183000Z DTSTAMP:20260422T212749Z UID:CMU-TP/42 DESCRIPTION:Title: Geometric soft theorems (part 2)\nby Julio Parra Martinez (Caltech) as part of Carnegie Mellon theoretical physics\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CMU-TP/42/ END:VEVENT BEGIN:VEVENT SUMMARY:Donal O'Connell (University of Edinburgh) DTSTART:20220323T163000Z DTEND:20220323T173000Z DTSTAMP:20260422T212749Z UID:CMU-TP/43 DESCRIPTION:by Donal O'Connell (University of Edinburgh) as part of Carneg ie Mellon theoretical physics\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CMU-TP/43/ END:VEVENT BEGIN:VEVENT SUMMARY:Mohit Randeria (Ohio State University) DTSTART:20220202T173000Z DTEND:20220202T183000Z DTSTAMP:20260422T212749Z UID:CMU-TP/44 DESCRIPTION:by Mohit Randeria (Ohio State University) as part of Carnegie Mellon theoretical physics\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CMU-TP/44/ END:VEVENT BEGIN:VEVENT SUMMARY:Anders Tranberg (University of Stavanger) DTSTART:20220518T163000Z DTEND:20220518T173000Z DTSTAMP:20260422T212749Z UID:CMU-TP/45 DESCRIPTION:by Anders Tranberg (University of Stavanger) as part of Carneg ie Mellon theoretical physics\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CMU-TP/45/ END:VEVENT BEGIN:VEVENT SUMMARY:Mustafa Amin (Rice University) DTSTART:20220516T170000Z DTEND:20220516T180000Z DTSTAMP:20260422T212749Z UID:CMU-TP/46 DESCRIPTION:Title: Small-Scale Structure in Vector Dark Matter\nby Mustafa Amin (Rice Uni versity) as part of Carnegie Mellon theoretical physics\n\n\nAbstract\nCan we figure out the spin of dark matter from astrophysical observations? I will talk about new phenomenology of (ultra)light vector dark matter incl uding (i) a new class of polarized vector solitons (ii) interference patt erns in density (iii) intrinsic spin. I will provide results for nonlinea r structure formation in vector dark matter where this phenomenology is na turally present. These effects lead to signals in astrophysics and direct detection that can potentially distinguish vector dark matter from their scalar counterpart. Time permitting\, I will discuss the generalization of above phenomenology to higher spin bosonic fields.\n LOCATION:https://researchseminars.org/talk/CMU-TP/46/ END:VEVENT END:VCALENDAR