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:20260404T095036Z 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/C osmology Seminar\n\n\nAbstract\nIn AdS/CFT\, we know that relevant operato rs\, for instance a scalar source\, can drastically change the bulk geomet ry. Normally one is only interested in what happens outside the horizon\, but during this talk I will dive inside various black holes and discuss th e effects of relevant operators. The dynamics turns out to be rather intri cate with even fractal-like behaviour emerging. Furthermore\, we will see that generically\, Cauchy horizons will be replaced by a spacelike singula rity in the presence of a relevant scalar source. This motivates a notion of ‘holographic’ cosmic censorship. This talk is based on 2006.10056 a nd 2008.12786.\n LOCATION:https://stable.researchseminars.org/talk/uw_madison_theoryseminar s/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Juan S. Cruz (Technical University Munich) DTSTART:20201002T190000Z DTEND:20201002T200000Z DTSTAMP:20260404T095036Z UID:uw_madison_theoryseminars/3 DESCRIPTION:Title: Gradient effects on false vacuum decay in gauge t heory\nby Juan S. Cruz (Technical University Munich) as part of UW Mad ison High-Energy/Cosmology Seminar\n\n\nAbstract\nWe study false vacuum de cay for a gauged complex scalar field in a polynomial potential with nearl y degenerate minima. Radiative corrections to the profile of the nucleated bubble as well as the full decay rate are computed in the planar thin-wal l approximation using the effective action. This allows to account for the inhomogeneity of the bounce background and the radiative corrections in a self-consistent manner. In contrast to scalar or fermion loops\, for gaug e fields one must deal with a coupled system that mixes the Goldstone boso n and the gauge fields\, which considerably complicates the numerical calc ulation of Green's functions. In addition to the renormalization of coupli ngs\, we employ a covariant gradient expansion in order to systematically construct the counterterm for the wave-function renormalization. The resul t for the full decay rate however does not rely on such an expansion and a ccounts for all gradient corrections at the chosen truncation of the loop expansion. The ensuing gradient effects are shown to be of the same order of magnitude as non-derivative one-loop corrections.\n LOCATION:https://stable.researchseminars.org/talk/uw_madison_theoryseminar s/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Arjun Kar DTSTART:20201016T190000Z DTEND:20201016T200000Z DTSTAMP:20260404T095036Z UID:uw_madison_theoryseminars/5 DESCRIPTION:Title: Islands\, cosmology\, and baby universes\nby Arjun Kar as part of UW Madison High-Energy/Cosmology Seminar\n\n\nAbstrac t\nI will present a "minimal" model of black hole evaporation which uses r eplica wormholes and the island formula to recover the unitary Page curve. This model combines advantageous features of previous models of evaporat ion to give a more flexible formalism. As an example of its flexibility\, I will discuss its application to de Sitter black holes\, where the islan d formula yields results which seem to be in tension with some old expecta tions about quantum gravity in de Sitter space. Finally\, time permitting \, I will describe more general implications of wormholes in the gravitati onal path integral by extending a toy model of Marolf and Maxfield to incl ude spin structure. The inclusion of spin structure presents interesting complications when constructing the baby universe Hilbert space\, as well as the dual of a single boundary theory.\n LOCATION:https://stable.researchseminars.org/talk/uw_madison_theoryseminar s/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Jeff Dror (UC Berkeley) DTSTART:20201023T190000Z DTEND:20201023T200000Z DTSTAMP:20260404T095036Z UID:uw_madison_theoryseminars/6 DESCRIPTION:Title: New roads to discovery of light states\nby Je ff Dror (UC Berkeley) as part of UW Madison High-Energy/Cosmology Seminar\ n\n\nAbstract\nLight particles can imprint themselves on our detectors in spectacular and often subtle ways. In this talk\, I will present two new p robes of hidden sectors. In the first part\, I consider the prospect of se eing a relativistic background of axions\, a so-called "cosmic axion backg round" (CaB). This background can have a range of possible cosmic sources and I consider several possible mechanisms (with the most well known being thermal production). Furthermore\, I will show that with dedicated search es\, a CaB may be detectable with cavity experiments such as ADMX or DM-ra dio. In the second part\, I revisit phenomenology of leptonic gauge bosons (such as Lmu-Ltau) showing that they couple to a non-conserved current.Th is property can be used to show that in the high energy limit\, these gaug e bosons are equivalent to majorons. This allows them to be discovered usi ng several new probes including neutrino decays\, meson decays\, neutrinol ess double beta decay searches\, and neutrino annihilations in thermal sys tems. These bounds drastically shape the parameter space of these theories .\n LOCATION:https://stable.researchseminars.org/talk/uw_madison_theoryseminar s/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Marija Tomašević (Universitat de Barcelona) DTSTART:20201030T190000Z DTEND:20201030T200000Z DTSTAMP:20260404T095036Z UID:uw_madison_theoryseminars/7 DESCRIPTION:Title: Quantum Penrose Inequality\nby Marija Tomaše vić (Universitat de Barcelona) as part of UW Madison High-Energy/Cosmolog y Seminar\n\n\nAbstract\nAccording to the classical Penrose inequality\, t he mass at spatial infinity is bounded from below by a function of the are a of certain trapped surfaces. We exhibit quantum field theory states that violate this relation at the semiclassical level. We formulate a Quantum Penrose Inequality by replacing the area with the generalized entropy of t he light-sheet of an appropriate quantum trapped surface. We perform a num ber of nontrivial tests of our proposal\, and we consider and rule out alt ernative formulations. We also discuss the relation to weak cosmic censors hip.\n LOCATION:https://stable.researchseminars.org/talk/uw_madison_theoryseminar s/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Oliver Janssen (ICTP\, Trieste) DTSTART:20201113T200000Z DTEND:20201113T210000Z DTSTAMP:20260404T095036Z UID:uw_madison_theoryseminars/8 DESCRIPTION:Title: Two topics in quantum gravity\nby Oliver Jans sen (ICTP\, Trieste) as part of UW Madison High-Energy/Cosmology Seminar\n \n\nAbstract\nI will discuss two topics in quantum gravity\, both involvin g the gravitational path integral. In the first part I will introduce the “no-boundary wave function”\, a path integral over geometries on compa ct four-manifolds which solves the Wheeler-DeWitt equation. I will then ou tline how this object can be computed\, and comment on its interpretation\ , in the scenario of minimally coupled scalar field matter subject to a po tential energy function of the slow-roll type. In the second part I will c omment on a proposal which identifies bulk gravitational path integrals wi th ensemble averages of boundary partition functions.\nThis talk is based on 2009.06282 and work in progress.\n LOCATION:https://stable.researchseminars.org/talk/uw_madison_theoryseminar s/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Kevin Kelly (Fermilab) DTSTART:20201106T200000Z DTEND:20201106T210000Z DTSTAMP:20260404T095036Z UID:uw_madison_theoryseminars/9 DESCRIPTION:Title: Heavy Neutrinos and Where to Find Them\nby Ke vin Kelly (Fermilab) as part of UW Madison High-Energy/Cosmology Seminar\n \n\nAbstract\nThe discovery of neutrino oscillations led to a new understa nding that neutrinos have mass\, which requires physics beyond the Standar d Model. One well-motivated and well-studied solution is that right handed neutrinos exist and interact in a way that generates light neutrino masse s. Moreover\, if these new neutrinos are “Heavy”\, there is potential for explaining why the Standard Model neutrinos are so much lighter than t he charged leptons and quarks. I will summarize current searches for these heavy neutrinos across a wide range of masses and then focus on a particu lar regime of interest — GeV-scale Heavy Neutrinos. I will demonstrate h ow neutrino oscillation experiments can serve as a great environment to fi nd these hypothetical particles in the coming decade. If we are lucky enou gh to discover these particles\, then understanding them will become of pa ramount importance to the particle physics community. I will show strategi es for exploring two specific characteristics of these heavy neutrinos by studying their decays: whether or not Lepton number is conserved (or wheth er they are Dirac or Majorana fermions)\, and what types of particle/parti cles mediate their interactions.\n LOCATION:https://stable.researchseminars.org/talk/uw_madison_theoryseminar s/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Ben Stefanek (Mainz Institute for Theoretical Physics) DTSTART:20201009T190000Z DTEND:20201009T200000Z DTSTAMP:20260404T095036Z UID:uw_madison_theoryseminars/10 DESCRIPTION:Title: Gravitational wave probes of axion-like particle s\nby Ben Stefanek (Mainz Institute for Theoretical Physics) as part o f UW Madison High-Energy/Cosmology Seminar\n\n\nAbstract\nConventional app roaches to probing axions and axion-like particles (ALPs) typically rely o n a coupling to photons. However\, if this coupling is extremely weak\, AL Ps become invisible and are effectively decoupled from the Standard Model. Such particles\, which are viable candidates for dark matter\, can also p roduce a stochastic gravitational wave (GW) background in the early univer se. This occurs if the axion couples to a dark gauge boson that experience s a tachyonic instability when the axion begins to oscillate. This instabi lity exponentially amplifies vacuum fluctuations of a single dark photon h elicity\, resulting in a rapidly time-varying\, anisotropic energy distrib ution that sources chiral GWs. We identify the regions of ALP parameter sp ace which may be probed by future GW detectors\, including ground- and spa ce-based interferometers and pulsar timing arrays. Interestingly\, these e xperiments have the ability to probe axions from the bottom up\, i.e. in t he very weakly coupled regime which is otherwise unconstrained. A smoking gun for the model is the completely chiral nature of the GW peak\, which c ould be detected by LISA or Einstein Telescope if the signal amplitude is large.\n LOCATION:https://stable.researchseminars.org/talk/uw_madison_theoryseminar s/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Horng Sheng Chia (Institute for Advanced Studies) DTSTART:20200925T190000Z DTEND:20200925T200000Z DTSTAMP:20260404T095036Z UID:uw_madison_theoryseminars/11 DESCRIPTION:Title: Probing Particle Physics with Gravitational Wave s\nby Horng Sheng Chia (Institute for Advanced Studies) as part of UW Madison High-Energy/Cosmology Seminar\n\n\nAbstract\nGravitational wave as tronomy will transform astrophysics in many ways\; can it do the same for particle physics? In this talk\, I will describe how the gravitational wav es emitted by binary systems offer us a new window onto physics beyond the Standard Model. I will focus on a specific class of new physics called ul tralight bosons\, which can spontaneously form boson clouds around rotatin g black holes. Remarkably\, the dynamics of these clouds in binary systems can be formulated as “scattering events” that are quantified by a “ S-matrix”. Furthermore\, the signatures emitted by these binary systems allow us to infer the masses and intrinsic spins of these ultralight boson s\, making binary black holes novel detectors for these putative new field s. I will end with a brief discussion on probes of other types of new phys ics\, including current efforts to search for these novel signatures in th e data.\n LOCATION:https://stable.researchseminars.org/talk/uw_madison_theoryseminar s/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Edgar Shaghoulian (University of Pennsylvania) DTSTART:20201204T200000Z DTEND:20201204T210000Z DTSTAMP:20260404T095036Z UID:uw_madison_theoryseminars/12 DESCRIPTION:Title: Replica wormholes\, the black hole information p aradox\, and cosmology\nby Edgar Shaghoulian (University of Pennsylvan ia) as part of UW Madison High-Energy/Cosmology Seminar\n\n\nAbstract\nI w ill introduce the black hole information paradox and briefly review the ro le that replica wormholes play in obtaining black hole evolution consisten t with unitarity. I will then discuss general consistency conditions that guide the search for such nontrivial saddles in the gravitational path int egral\, with several examples in cosmological spacetimes.\n LOCATION:https://stable.researchseminars.org/talk/uw_madison_theoryseminar s/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Sungwoo Hong (Cornell University) DTSTART:20201211T200000Z DTEND:20201211T210000Z DTSTAMP:20260404T095036Z UID:uw_madison_theoryseminars/13 DESCRIPTION:Title: Electric-Magnetic S-matrix\nby Sungwoo Hong (Cornell University) as part of UW Madison High-Energy/Cosmology Seminar\n \n\nAbstract\nIn the first part of the talk\, I will argue that an asympto tic multi-particle state built as a product of one-particle states is not fully general. In addition\, I will show that the more general asymptotic multi-particle state carries extra quantum number\, pairwise-helicity\, on top of the regular labels such as momentum and spin/helicity of each part icle. In the second part of the talk\, the S-matrix for the scattering of electrically and magnetically charged particles will be considered. After discussing several non-conventional properties of the electric-magnetic S- matrix\, including the extra pairwise-helicity carried by the electric-mag netic asymptotic state and the associated crossing symmetry violation\, mo dern on-shell scattering amplitude method will be motivated as a way to co nstruct the electric-magnetic S-matrix. Pairwise spinor-helicity variables as additional building blocks for the electric-magnetic S-matrix will the n be introduced. Discussion on the general three-point amplitudes and resu lting generalized spin-helicity selection rules comes next. Finally\, I de scribe the partial-wave decomposition of the 2 to 2 electric-magnetic S-ma trix\, showing that the well-known results based on QM computations are re produced with a small input about the phase shift. In particular\, the hel icity-flip in the lowest partial wave is shown to be a simple consequence of a generalized spin-helicity selection rule. Furthermore\, the full angu lar dependence for the higher partial waves is shown to agree with QM resu lts. Our work represents a remarkable success of on-shell methods for non- perturbative physics\, especially when the Lagrangian description fails.\n LOCATION:https://stable.researchseminars.org/talk/uw_madison_theoryseminar s/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Henry Maxfield (UCSB) DTSTART:20201218T200000Z DTEND:20201218T210000Z DTSTAMP:20260404T095036Z UID:uw_madison_theoryseminars/14 DESCRIPTION:Title: Observations of Hawking radiation: the Page curv e and baby universes\nby Henry Maxfield (UCSB) as part of UW Madison H igh-Energy/Cosmology Seminar\n\n\nAbstract\nI'll discuss recent progress i n black hole information\, using semiclassical gravity to compute the entr opy of Hawking radiation and finding the "Page curve" associated with a un itary quantum system with density of states given by the Bekenstein-Hawkin g formula. I will formulate this in terms of an operationally-defined noti on of entropy\, using a Lorentz-signature gravitational path integral in a symptotically flat spacetimes. I'll then explain the Hilbert space interpr etation of these calculations\, which requires the introduction of a Hilbe rt space of baby universes\, and results in superselection sectors for asy mptotic observers.\n LOCATION:https://stable.researchseminars.org/talk/uw_madison_theoryseminar s/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Chandramouli Chowdhury (ICTS\, Bangalore) DTSTART:20210129T200000Z DTEND:20210129T210000Z DTSTAMP:20260404T095036Z UID:uw_madison_theoryseminars/15 DESCRIPTION:Title: A physical protocol to obtain information in qua ntum gravity\nby Chandramouli Chowdhury (ICTS\, Bangalore) as part of UW Madison High-Energy/Cosmology Seminar\n\n\nAbstract\nWe consider a set of observers who live near the boundary of global AdS\, and are allowed to act only with simple low-energy unitaries and make measurements in a smal l interval of time. The observers are not allowed to leave the near-bounda ry region. We describe a physical protocol that nevertheless allows these observers to obtain detailed information about the bulk state. This protoc ol utilizes the leading gravitational back-reaction of a bulk excitation o n the metric\, and also relies on the entanglement-structure of the vacuum . For low-energy states\, we show how the near-boundary observers can use this protocol to completely identify the bulk state. We explain why the pr otocol fails completely in theories without gravity\, including non-gravit ational gauge theories. This provides perturbative evidence for the claim that one of the signatures of holography -- the fact that information abou t the bulk is also available near the boundary -- is already visible in se miclassical gravity. This is work done in collaboration with Olga Papadoul aki and Suvrat Raju\, in 2008.01740.\n LOCATION:https://stable.researchseminars.org/talk/uw_madison_theoryseminar s/15/ END:VEVENT END:VCALENDAR