BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Jorrit Kruthoff (Stanford University) DTSTART:20200918T190000Z DTEND:20200918T200000Z DTSTAMP:20260422T213046Z UID:uw_madison_theoryseminars/1 DESCRIPTION:Title: Classical aspects of black hole interiors\nby Jorrit Kruthoff (Stanford University) as part of UW Madison High-Energy/Cosmolog y Seminar\n\n\nAbstract\nIn AdS/CFT\, we know that relevant operators\, fo r instance a scalar source\, can drastically change the bulk geometry. Nor mally one is only interested in what happens outside the horizon\, but dur ing this talk I will dive inside various black holes and discuss the effec ts of relevant operators. The dynamics turns out to be rather intricate wi th even fractal-like behaviour emerging. Furthermore\, we will see that ge nerically\, Cauchy horizons will be replaced by a spacelike singularity in the presence of a relevant scalar source. This motivates a notion of ‘h olographic’ cosmic censorship. This talk is based on 2006.10056 and 2008 .12786.\n LOCATION:https://researchseminars.org/talk/uw_madison_theoryseminars/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Juan S. Cruz (Technical University Munich) DTSTART:20201002T190000Z DTEND:20201002T200000Z DTSTAMP:20260422T213046Z UID:uw_madison_theoryseminars/3 DESCRIPTION:Title: Gradient effects on false vacuum decay in gauge theory\nby Juan S. Cruz (Technical University Munich) as part of UW Madison Hi gh-Energy/Cosmology Seminar\n\n\nAbstract\nWe study false vacuum decay for a gauged complex scalar field in a polynomial potential with nearly degen erate minima. Radiative corrections to the profile of the nucleated bubble as well as the full decay rate are computed in the planar thin-wall appro ximation using the effective action. This allows to account for the inhomo geneity of the bounce background and the radiative corrections in a self-c onsistent manner. In contrast to scalar or fermion loops\, for gauge field s one must deal with a coupled system that mixes the Goldstone boson and t he gauge fields\, which considerably complicates the numerical calculation of Green's functions. In addition to the renormalization of couplings\, w e employ a covariant gradient expansion in order to systematically constru ct the counterterm for the wave-function renormalization. The result for t he full decay rate however does not rely on such an expansion and accounts for all gradient corrections at the chosen truncation of the loop expansi on. The ensuing gradient effects are shown to be of the same order of magn itude as non-derivative one-loop corrections.\n LOCATION:https://researchseminars.org/talk/uw_madison_theoryseminars/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Arjun Kar DTSTART:20201016T190000Z DTEND:20201016T200000Z DTSTAMP:20260422T213046Z UID:uw_madison_theoryseminars/5 DESCRIPTION:Title: Islands\, cosmology\, and baby universes\nby Arjun K ar as part of UW Madison High-Energy/Cosmology Seminar\n\n\nAbstract\nI wi ll present a "minimal" model of black hole evaporation which uses replica wormholes and the island formula to recover the unitary Page curve. This model combines advantageous features of previous models of evaporation to give a more flexible formalism. As an example of its flexibility\, I will discuss its application to de Sitter black holes\, where the island formu la yields results which seem to be in tension with some old expectations a bout quantum gravity in de Sitter space. Finally\, time permitting\, I wi ll describe more general implications of wormholes in the gravitational pa th integral by extending a toy model of Marolf and Maxfield to include spi n structure. The inclusion of spin structure presents interesting complic ations when constructing the baby universe Hilbert space\, as well as the dual of a single boundary theory.\n LOCATION:https://researchseminars.org/talk/uw_madison_theoryseminars/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Jeff Dror (UC Berkeley) DTSTART:20201023T190000Z DTEND:20201023T200000Z DTSTAMP:20260422T213046Z UID:uw_madison_theoryseminars/6 DESCRIPTION:Title: New roads to discovery of light states\nby Jeff Dror (UC Berkeley) as part of UW Madison High-Energy/Cosmology Seminar\n\n\nAb stract\nLight particles can imprint themselves on our detectors in spectac ular and often subtle ways. In this talk\, I will present two new probes o f hidden sectors. In the first part\, I consider the prospect of seeing a relativistic background of axions\, a so-called "cosmic axion background" (CaB). This background can have a range of possible cosmic sources and I c onsider several possible mechanisms (with the most well known being therma l production). Furthermore\, I will show that with dedicated searches\, a CaB may be detectable with cavity experiments such as ADMX or DM-radio. In the second part\, I revisit phenomenology of leptonic gauge bosons (such as Lmu-Ltau) showing that they couple to a non-conserved current.This prop erty can be used to show that in the high energy limit\, these gauge boson s are equivalent to majorons. This allows them to be discovered using seve ral new probes including neutrino decays\, meson decays\, neutrinoless dou ble beta decay searches\, and neutrino annihilations in thermal systems. T hese bounds drastically shape the parameter space of these theories.\n LOCATION:https://researchseminars.org/talk/uw_madison_theoryseminars/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Marija Tomašević (Universitat de Barcelona) DTSTART:20201030T190000Z DTEND:20201030T200000Z DTSTAMP:20260422T213046Z UID:uw_madison_theoryseminars/7 DESCRIPTION:Title: Quantum Penrose Inequality\nby Marija Tomašević (U niversitat de Barcelona) as part of UW Madison High-Energy/Cosmology Semin ar\n\n\nAbstract\nAccording to the classical Penrose inequality\, the mass at spatial infinity is bounded from below by a function of the area of ce rtain trapped surfaces. We exhibit quantum field theory states that violat e this relation at the semiclassical level. We formulate a Quantum Penrose Inequality by replacing the area with the generalized entropy of the ligh t-sheet of an appropriate quantum trapped surface. We perform a number of nontrivial tests of our proposal\, and we consider and rule out alternativ e formulations. We also discuss the relation to weak cosmic censorship.\n LOCATION:https://researchseminars.org/talk/uw_madison_theoryseminars/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Oliver Janssen (ICTP\, Trieste) DTSTART:20201113T200000Z DTEND:20201113T210000Z DTSTAMP:20260422T213046Z UID:uw_madison_theoryseminars/8 DESCRIPTION:Title: Two topics in quantum gravity\nby Oliver Janssen (IC TP\, Trieste) as part of UW Madison High-Energy/Cosmology Seminar\n\n\nAbs tract\nI will discuss two topics in quantum gravity\, both involving the g ravitational path integral. In the first part I will introduce the “no-b oundary wave function”\, a path integral over geometries on compact four -manifolds which solves the Wheeler-DeWitt equation. I will then outline h ow this object can be computed\, and comment on its interpretation\, in th e scenario of minimally coupled scalar field matter subject to a potential energy function of the slow-roll type. In the second part I will comment on a proposal which identifies bulk gravitational path integrals with ense mble averages of boundary partition functions.\nThis talk is based on 2009 .06282 and work in progress.\n LOCATION:https://researchseminars.org/talk/uw_madison_theoryseminars/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Kevin Kelly (Fermilab) DTSTART:20201106T200000Z DTEND:20201106T210000Z DTSTAMP:20260422T213046Z UID:uw_madison_theoryseminars/9 DESCRIPTION:Title: Heavy Neutrinos and Where to Find Them\nby Kevin Kel ly (Fermilab) as part of UW Madison High-Energy/Cosmology Seminar\n\n\nAbs tract\nThe discovery of neutrino oscillations led to a new understanding t hat neutrinos have mass\, which requires physics beyond the Standard Model . One well-motivated and well-studied solution is that right handed neutri nos exist and interact in a way that generates light neutrino masses. More over\, if these new neutrinos are “Heavy”\, there is potential for exp laining why the Standard Model neutrinos are so much lighter than the char ged leptons and quarks. I will summarize current searches for these heavy neutrinos across a wide range of masses and then focus on a particular reg ime of interest — GeV-scale Heavy Neutrinos. I will demonstrate how neut rino oscillation experiments can serve as a great environment to find thes e hypothetical particles in the coming decade. If we are lucky enough to d iscover these particles\, then understanding them will become of paramount importance to the particle physics community. I will show strategies for exploring two specific characteristics of these heavy neutrinos by studyin g their decays: whether or not Lepton number is conserved (or whether they are Dirac or Majorana fermions)\, and what types of particle/particles me diate their interactions.\n LOCATION:https://researchseminars.org/talk/uw_madison_theoryseminars/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Ben Stefanek (Mainz Institute for Theoretical Physics) DTSTART:20201009T190000Z DTEND:20201009T200000Z DTSTAMP:20260422T213046Z UID:uw_madison_theoryseminars/10 DESCRIPTION:Title: Gravitational wave probes of axion-like particles\n by Ben Stefanek (Mainz Institute for Theoretical Physics) as part of UW Ma dison High-Energy/Cosmology Seminar\n\n\nAbstract\nConventional approaches to probing axions and axion-like particles (ALPs) typically rely on a cou pling to photons. However\, if this coupling is extremely weak\, ALPs beco me invisible and are effectively decoupled from the Standard Model. Such p articles\, which are viable candidates for dark matter\, can also produce a stochastic gravitational wave (GW) background in the early universe. Thi s occurs if the axion couples to a dark gauge boson that experiences a tac hyonic instability when the axion begins to oscillate. This instability ex ponentially amplifies vacuum fluctuations of a single dark photon helicity \, resulting in a rapidly time-varying\, anisotropic energy distribution t hat sources chiral GWs. We identify the regions of ALP parameter space whi ch may be probed by future GW detectors\, including ground- and space-base d interferometers and pulsar timing arrays. Interestingly\, these experime nts have the ability to probe axions from the bottom up\, i.e. in the very weakly coupled regime which is otherwise unconstrained. A smoking gun for the model is the completely chiral nature of the GW peak\, which could be detected by LISA or Einstein Telescope if the signal amplitude is large.\ n LOCATION:https://researchseminars.org/talk/uw_madison_theoryseminars/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Horng Sheng Chia (Institute for Advanced Studies) DTSTART:20200925T190000Z DTEND:20200925T200000Z DTSTAMP:20260422T213046Z UID:uw_madison_theoryseminars/11 DESCRIPTION:Title: Probing Particle Physics with Gravitational Waves\n by Horng Sheng Chia (Institute for Advanced Studies) as part of UW Madison High-Energy/Cosmology Seminar\n\n\nAbstract\nGravitational wave astronomy will transform astrophysics in many ways\; can it do the same for particl e physics? In this talk\, I will describe how the gravitational waves emit ted by binary systems offer us a new window onto physics beyond the Standa rd Model. I will focus on a specific class of new physics called ultraligh t bosons\, which can spontaneously form boson clouds around rotating black holes. Remarkably\, the dynamics of these clouds in binary systems can be formulated as “scattering events” that are quantified by a “S-matri x”. Furthermore\, the signatures emitted by these binary systems allow u s to infer the masses and intrinsic spins of these ultralight bosons\, mak ing binary black holes novel detectors for these putative new fields. I wi ll end with a brief discussion on probes of other types of new physics\, i ncluding current efforts to search for these novel signatures in the data. \n LOCATION:https://researchseminars.org/talk/uw_madison_theoryseminars/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Edgar Shaghoulian (University of Pennsylvania) DTSTART:20201204T200000Z DTEND:20201204T210000Z DTSTAMP:20260422T213046Z UID:uw_madison_theoryseminars/12 DESCRIPTION:Title: Replica wormholes\, the black hole information paradox\ , and cosmology\nby Edgar Shaghoulian (University of Pennsylvania) as part of UW Madison High-Energy/Cosmology Seminar\n\n\nAbstract\nI will int roduce the black hole information paradox and briefly review the role that replica wormholes play in obtaining black hole evolution consistent with unitarity. I will then discuss general consistency conditions that guide t he search for such nontrivial saddles in the gravitational path integral\, with several examples in cosmological spacetimes.\n LOCATION:https://researchseminars.org/talk/uw_madison_theoryseminars/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Sungwoo Hong (Cornell University) DTSTART:20201211T200000Z DTEND:20201211T210000Z DTSTAMP:20260422T213046Z UID:uw_madison_theoryseminars/13 DESCRIPTION:Title: Electric-Magnetic S-matrix\nby Sungwoo Hong (Cornel l University) as part of UW Madison High-Energy/Cosmology Seminar\n\n\nAbs tract\nIn the first part of the talk\, I will argue that an asymptotic mul ti-particle state built as a product of one-particle states is not fully g eneral. In addition\, I will show that the more general asymptotic multi-p article state carries extra quantum number\, pairwise-helicity\, on top of the regular labels such as momentum and spin/helicity of each particle. I n the second part of the talk\, the S-matrix for the scattering of electri cally and magnetically charged particles will be considered. After discuss ing several non-conventional properties of the electric-magnetic S-matrix\ , including the extra pairwise-helicity carried by the electric-magnetic a symptotic state and the associated crossing symmetry violation\, modern on -shell scattering amplitude method will be motivated as a way to construct the electric-magnetic S-matrix. Pairwise spinor-helicity variables as add itional building blocks for the electric-magnetic S-matrix will then be in troduced. Discussion on the general three-point amplitudes and resulting g eneralized spin-helicity selection rules comes next. Finally\, I describe the partial-wave decomposition of the 2 to 2 electric-magnetic S-matrix\, showing that the well-known results based on QM computations are reproduce d with a small input about the phase shift. In particular\, the helicity-f lip in the lowest partial wave is shown to be a simple consequence of a ge neralized spin-helicity selection rule. Furthermore\, the full angular dep endence for the higher partial waves is shown to agree with QM results. Ou r work represents a remarkable success of on-shell methods for non-perturb ative physics\, especially when the Lagrangian description fails.\n LOCATION:https://researchseminars.org/talk/uw_madison_theoryseminars/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Henry Maxfield (UCSB) DTSTART:20201218T200000Z DTEND:20201218T210000Z DTSTAMP:20260422T213046Z UID:uw_madison_theoryseminars/14 DESCRIPTION:Title: Observations of Hawking radiation: the Page curve and b aby universes\nby Henry Maxfield (UCSB) as part of UW Madison High-Ene rgy/Cosmology Seminar\n\n\nAbstract\nI'll discuss recent progress in black hole information\, using semiclassical gravity to compute the entropy of Hawking radiation and finding the "Page curve" associated with a unitary q uantum system with density of states given by the Bekenstein-Hawking formu la. I will formulate this in terms of an operationally-defined notion of e ntropy\, using a Lorentz-signature gravitational path integral in asymptot ically flat spacetimes. I'll then explain the Hilbert space interpretation of these calculations\, which requires the introduction of a Hilbert spac e of baby universes\, and results in superselection sectors for asymptotic observers.\n LOCATION:https://researchseminars.org/talk/uw_madison_theoryseminars/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Chandramouli Chowdhury (ICTS\, Bangalore) DTSTART:20210129T200000Z DTEND:20210129T210000Z DTSTAMP:20260422T213046Z UID:uw_madison_theoryseminars/15 DESCRIPTION:Title: A physical protocol to obtain information in quantum gr avity\nby Chandramouli Chowdhury (ICTS\, Bangalore) as part of UW Madi son High-Energy/Cosmology Seminar\n\n\nAbstract\nWe consider a set of obse rvers who live near the boundary of global AdS\, and are allowed to act on ly with simple low-energy unitaries and make measurements in a small inter val of time. The observers are not allowed to leave the near-boundary regi on. We describe a physical protocol that nevertheless allows these observe rs to obtain detailed information about the bulk state. This protocol util izes the leading gravitational back-reaction of a bulk excitation on the m etric\, and also relies on the entanglement-structure of the vacuum. For l ow-energy states\, we show how the near-boundary observers can use this pr otocol to completely identify the bulk state. We explain why the protocol fails completely in theories without gravity\, including non-gravitational gauge theories. This provides perturbative evidence for the claim that on e of the signatures of holography -- the fact that information about the b ulk is also available near the boundary -- is already visible in semiclass ical gravity. This is work done in collaboration with Olga Papadoulaki and Suvrat Raju\, in 2008.01740.\n LOCATION:https://researchseminars.org/talk/uw_madison_theoryseminars/15/ END:VEVENT END:VCALENDAR