The AdS/CFT correspondence conjectures a duality between a theory of quantum gravity in Anti de Sitter space and a conformal field theory. Susskind identified an interesting paradox in this correspondence: namely some aspects of the behavior of eternal black holes, which partition space-time into two distinct regions connected by a “wormhole”, do not have an obvious CFT analogue. The conundrum is that the volume of the wormhole grows for a very long time, whereas in the dual space the CFT dynamics of most black hole systems are conjectured to be “scrambling” --- the expectation values of local operators saturate very quickly to their equilibrium values. What quantity in the CFT could possibly then be dual to the wormhole volume? Susskind conjectured that the dual quantity is the circuit complexity of the CFT state, which continues to increase even after the system equilibriates.

But Susskind's conjecture raises its own issues --- we show that for the kinds of quantum states in the CFT, their quantum circuit complexity is exponentially hard to approximate, whereas in the dual AdS space, the wormhole volume can be efficiently approximated. Or to put it in other words, the circuit complexity of the CFT states is not “feelable”, that is, it is not a quantity which can be observed with polynomial-time quantum experiments, in contrast to wormhole volume. One consequence is that the dictionary map which exhibits the AdS/CFT correspondence must itself be exponentially hard to compute. Formally, a key part of this argument appeals to a fundamental notion from cryptography known as computational pseudorandomness, where ensembles of states of low circuit complexity can masquerade as high complexity states to any casual observer.

The talk will be self contained and will include an introduction to the basic notions of computational pseudorandomness.

Based on joint work with Adam Bouland and Bill Fefferman.

**Organizers: Sanjeev Arora, Curtis Callan, and Victor Mikhaylov **“Deep learning” refers to use of neural networks to solve learning problems, including “learning” hidden structures in large and complex data sets. The theory for this field is still in its infancy. Lately physical and biological scientists have begun to explore how it might apply to their domains. This seminar series seeks to introduce the theoretical science community in Princeton and surrounding regions to the practice, promise, and problems of deep learning. It will consist of monthly afternoon sessions ---geared to the broader scientific community--- that will feature an invited talk followed by informal discussions among participants. The schedule will be updated whenever dates for new speakers are confirmed.This seminar series is coordinated with the “Special Year on Optimization, Statistics, and Theoretical Machine Learning” at the Institute for Advanced Study (under the direction of co-organizer Sanjeev Arora).**Register here: **http://pcts.princeton.edu/programs/current/deep-learning-for-physics-seminar-series/121

We will introduce ourselves and give a 2 minute description of what we are interested in at the moment.

The plan for future group meetings is to have some review talks, or topics for discussions. So please think about suggestions for things you would like to see discussed at future meetings. You can also think whether you want to volunteer for leading one of the discussions.

Conformal Field Theory (CFT) is a framework used to describe physical systems with no intrinsic length or energy scales. CFTs have wide applicability across theoretical physics, ranging from critical points in the phase diagrams of water or magnetic materials to the low-energy dynamics of extended objects in string theory. In this talk, I will begin by describing how CFTs can be used to understand critical phenomena. I will then discuss recent ideas that led to tremendous progress in obtaining a quantitative understanding of various corners in the space of all possible CFTs. I will end by discussing how CFTs can be used to describe and learn about Quantum Gravity in the presence of a negative cosmological constant.

We present a first-principles derivation of a weak-strong duality between the four-dimensional fishnet theory in the planar limit and a discretized string-like model living in AdS5. At strong coupling, the dual description becomes classical and we demonstrate explicitly the classical integrability of the model. We test our results by reproducing the strong coupling limit of the 4-point correlator computed before non-perturbatively from the conformal partial wave expansion. Next, by applying the canonical quantization procedure with constraints, we show that the model describes a quantum integrable chain of particles propagating in AdS5. Finally, we reveal a discrete reparametrization symmetry of the model and reproduce the spectrum when known analytically. Due to the simplicity of our model, it could provide an ideal playground for holography. Furthermore, since the fishnet model and N=4 SYM theory are continuously linked our consideration could shed light on the derivation of AdS/CFT for the latter. This talk is based on recent work with Nikolay Gromov.

In the next decade, improvements in the CMB and Large Scale Structure (LSS) measurements will make the universe an excellent laboratory for neutrino physics. Besides knowing the sum of neutrino masses, we can better answer questions about neutrino properties, such as how long the SM neutrinos can live? In this talk, I will explain the LSS signals of neutrino decay and show that the next generation LSS and CMB lensing measurements can either extend the lifetime bound on SM neutrinos to a cosmological time scale, or probe the distinct signatures of neutrino decay.

This talk will give a brief overview focused on six papers written by D. Gaiotto, G. Moore, and A. Neitzke

loosely centered around the topics mentioned in the title. The papers are on the arXiv.

Background reading: Some short reviews are:

https://arxiv.org/pdf/1211.2331.pdf

https://arxiv.org/pdf/1308.2198.pdf

https://arxiv.org/pdf/1412.7120.pdf

Some pedagogical/summer school lecture notes can be found in talks # 31, 35, 47, 84 on the home page of G. Moore:

http://www.physics.rutgers.edu/~gmoore/

Multiparticle production is studied experimentally and theoretically in QCD that describes interactions in the language of quarks and gluons. In the experiment the real hadrons are registered. For transfer from quarks and gluons to observed hadrons various phenomenological models are used.In order to describe the high multiplicity region, we offer a gluon dominance model (GDM). It represents a convolution of two stages. First stage is described as a part of QCD. For second one (hadronisation), the phenomenological model is used. To describe hadronisation, a scheme has been proposed, consistent with experimental data in the region of its dominance. Comparison of this model with data on $*e^*+*e^*-$ annihilation over a wide energy interval (up to 200 GeV) confirms the fragmentation mechanism of hadronisation, the development of the quark-gluon cascade with energy increase with a domination of bremsstrahlung gluons.The description of topological cross sections in $*pp$ *collisions within of GDM testifies that in hadron collisions the mechanism of hadronisation is being replaced by the recombination one. At that point, gluons play an active role in the multiparticle production process, and valence quarks are passive. They stay in the leading particles, and only the gluon splitting is responsible for the region of high multiplicity.GDM with inclusion of intermediate quark charged topologies describes topological cross sections in a proton-antiptoton annihilation and explains linear growth of a secondary correlative momentum in the negative area.The scaled variance of a neutral pion number mesuared by us is rising abruptly in the region of high total multiplicity and differs from Monte Carlo predictions by seven standard deviations. The growth of fluctuations of the neutral pion number in this region may indicate the formation of a pion (Bose-Einstein) condensate. Despite the growth of fluctuations on the neutral number, their average remains equal to 1/3 of the total pion number.

Quantising a black hole can be done starting with conventional physics. We just assume matter to keep the form of point particles until they come close to the horizon. The gravitational back reaction of these particles generates a novel relation between particles going in and particles going out, enabling us to transform in-going particles into out-going ones. This transformation removes “firewalls” along the future and past horizons, but it strongly affects space-time inside a black hole. It subsequently allows us, and indeed forces us, to identify antipodal points on the horizon. We argue that this exotic modification of the boundary condition is the only way to restore unitarity for the quantum evolution operator, and to identify the black hole microstates. Some mysteries, however, remain unresolved.

In this talk, based on work with S. Gubser, Z. Ji, B. Trundy, and A. Yarom, I present a scalar theory described by an action given in terms of a bi-local integral of a power law factor, with an exponent parameter s, multiplied by the squared arc length between points on the target manifold. Depending on the choice of s and of dimension, the theory can reduce to the usual sigma model, higher derivative versions thereof, or to a non-local theory with potential applications to the dynamics of M2-branes. I will also discuss the renormalization of the theory at one-loop level.

The dynamics and spread of quantum information in complex many-body systems is presently attracting

a lot of attention across various fields, ranging from cold atom physics via condensed quantum matter

to high energy physics and quantum gravity. This includes questions of how a quantum system thermalizes

and phenomena like many-body interference and localization, more generally non-classicality in many-particle

quantum physics. Here concepts that are based on echoes, i.e. rewinding time, provide a useful way to monitor complex quantum dynamics and its stability. Central to these developments are so-called out-of-time-order correlators (OTOCs) as sensitive probes for chaos and the temporal growth of complexity in interacting systems.

We will address such phenomena for quantum critical and quantum chaotic systems using semiclassical path

integral techniques based on interfering Feynman paths, thereby bridging the classical and quantum many-body world and allowing for deriving random matrix results. These methods enable us to compute echoes and

OTOCs including entanglement and correlation effects. Moreover, on the numerical side we devise a

semiclassical method for Bose-Hubbard systems far-out-of equilibrium that allows us to calculate many-body

quantum interference on time scales far beyond the famous Ehrenfest/scrambling time.

I will discuss walking behavior in gauge theories and weakly first order phase transition in statistical models. Despite being phenomena appearing in very different physical systems, they both show a region of approximate scale invariance. They can be understood as a RG flow passing between two fixed points living at complex couplings, which we call complex CFTs. By using conformal perturbation theory, knowing the conformal data of the complex CFTs allows us to make predictions on the observables of the walking theory. I will also discuss some two-dimensional examples.

Recent work has introduced a correspondence between jets and natural languages. In this talk, I will review how machine learning, with this natural language processing point of view, is changing the way we are thinking about jets. First, I will describe a very effective model for classification and regression tasks. Next, I will introduce a simplified model to aid in machine learning research for jet physics, that captures the essential ingredients of parton shower generators in full physics simulations. I will discuss how this line of research provides new insights into jets substructure and could lead to a systematic fit of a physics model to data.

This is a satellite event in association with the annual `Origins of the Universe' conference that takes place Sept 26-27, 2019 at the Simons Foundation in New York City's Flatiron District.

Confirmed Speakers:

- Bruce Allen (Max Planck Institute for Gravitational Physics)
- Beverly Berger (Stanford University)
- Thibault Damour (IHES)
- Karsten Danzmann (Max Planck Institute for Gravitational Physics)
- Sean McWilliams (West Virginia University)
- Slava Mukhanov (Ludwig-Maximilians-University, Munich)
- Igor Rodnianski (Princeton University)
- Richard Woodard (University of Florida, Gainesville)

I will discuss recent progress about the Cardy-like asymptotics of 4d supersymmetric index on S^3, also known as superconformal index. The main observation is that Bose-Fermi cancellation that trivializes the asymptotic expression of the index can be obstructed by complexifying chemical potentials. Applied to N=4 SYM, the new asymptotic free energy reproduces the Bekenstein-Hawking entropy of the known 1/16 BPS black hole in AdS5. If time permits, I will also talk about some circumstantial evidences for new BPS black holes. (References: 1810.12067, 1811.08646, 1904.03455.)

Using our state-of-the-art code Fornax we have simulated the collapse and explosion of the cores of many massive-star models in three spatial dimensions. This is the most comprehensive set of realistic 3D core-collapse supernova simulations yet performed and has provided very important insights into the mechanism and character of this 50-year-old astrophysical puzzle. I will present detailed results from this suite of runs and the novel conclusions derived from our new capacity to simulate many 3D, as opposed to 2D and 1D, full physics models every year. This new capability, enabled by this new algorithm and modern HPC assets, is poised to transform our understanding of this central astrophysical puzzle.

We review a recent geometric formulation of the tree-level S-matrix of various quantum field theories, including gauge and gravity theories, in terms of intersection numbers of twisted cohomology groups on the moduli space of genus-zero curves with marked points. Scattering amplitudes are computed in terms of integrals over such moduli spaces that localize on worldsheets resembling Feynman diagrams and in certain circumstances coincide with the field-theory limit of string theory. We outline recursion relations that allow for explicit computations of S-matrices on the forgetful fibration of moduli spaces. We show that in the massless limit intersection numbers have another localization formula on the critical points of a certain Morse function.

We construct a general form for an F-theory Weierstrass model over any base giving a 6D or 4D supergravity theory with gauge group SU(3) x SU(2) x U(1) / Z_6 and associated generic matter. The concept of 'generic matter' can be rigorously defined in 6D supergravity and generalizes naturally to four dimensions for F-theory models. We describe general F-theory models with this gauge group and the associated generic matter content, which fit into two distinct classes, and present an explicit Weierstrass model that realizes these models as two distinct branches. We also discuss, as a special case, the class of models recently studied by Cvetic, Halverson, Lin, Liu, and Tian, for which we demonstrate explicitly the possibility of unification through an SU(5) unHiggsing.

My talk is devoted to studies of large N saddle point structures in the SYK model beyond the commonly used approximations, in particular the replica-diagonal assumption and the conformal limit. We will discuss new solutions of the saddle point equations in the SYK and their role in physics of the model and in the gravity dual description. We will focus on the replica-nondiagonal exact saddle points, which introduce small nonperturbative effects in the 1/N expansion of SYK. We will consider their properties and implications for the gravity dual, a UV completion of JT gravity.

The talk is based on papers arXiv:1811.04831, arXiv:1905.04203 and on current work in progress.

Axion and Axion-like particles are fascinating dark matter candidates and a great effort has been devoted to their study, both theoretically and experimentally. In this talk I will discuss two different astrophysical searches. The first one consists in looking with radio telescopes for the spontaneous decay of axion dark matter using different targets as Dwarf Galaxies, Clusters or the Galactic Center. The second one uses the parity violating axion interactions to exploit the extreme precision of pulsar timing measurements and look for oscillations in the polarization angle of the pulsar signal.

Gauge/gravity duality relates certain strongly coupled CFTs with large effective central charge to semi-classical gravitational theories with AdS asymptotics. I will describe recent progress in understanding gravity duals for CFTs on non-trivial spacetimes with black hole horizons. Such gravity methods provide powerful new tools to access the physics of these strongly coupled theories, which often differs qualitatively from that found at weak coupling. I will then use some of the intuition gather from these studies to motivate the existence of static black holes in Randall-Sundrum II braneworlds. If time permits, I will discuss some of its properties such as dynamical stability.Reading material: arXiv:1104.4489, arXiv:1105.2558, arXiv:1208.6291, arXiv:1212.4820, arXiv:1405.2078, arXiv:1604.04832

Moiré patterns are ubiquitous in layered van der Waals materials and can now be fabricated with considerable control by combining mechanical exfoliation of van der Waals layers with tear and stack device fabrication techniques. I will explain why the electronic and optical properties of two-dimensional semiconductors and semimetals are strongly altered in long-period moiré superlattices, focusing in particular on the remarkable example of twisted bilayer graphene. When twisted to a magic [1] relative orientation angle near 1 degree the moiré superlattice minibands of bilayer graphene become extremely narrow and electronic correlations become strong. Experimental studies [2] of magic-angle twisted bilayer graphene (MATBG) have demonstrated that the electronic ground state can be a superconductor, a metal, or an insulator, depending on the filling of the magic angle flat bands. Insulating states occur close to most integer values of the number of electrons per moiré superlattice period, whereas superconducting states are common at fractional moiré band filling factors. In some cases, the insulating states are purely orbital ferromagnets that exhibit a quantum anomalous Hall effect and have superlattice bands with non-zero topological Chern indices C. I will discuss progress that has been made toward understanding these remarkable properties.[1] Moire bands in twisted double-layer graphene, R. Bistritzer and A.H. MacDonald, PNAS 108, 12233 (2011). [2] Magic-angle graphene superlattices: a new platform for unconventional superconductivity, Y. Cao et al. Nature (2018).

This talk will review the structure of closed superstring scattering amplitudes with particular emphasis on the constraints imposed by various dualities. This leads to precise determination of the coefficients of low order terms in the low energy expansion of amplitudes in theories with maximal supersymmetry. Among other things, these results provide "data" that should be matched by the holographic connections with conformal field theories.

It is widely believed that long after gravitational collapse, the external geometry of black holes relaxes to the Kerr-Newman solution. In contrast, the interior geometry is not unique and depends on initial conditions. I will discuss universal features of the interior of one-sided black holes in asymptotically flat space with a scalar field. In particular, I will argue that generically there exists effective gravitational shocks at the would-be inner horizon, a singular Cauchy horizon, and a spacelike singularity at r = 0.

Lifshitz scaling is an anisotropic scaling where time and space scale differently. Quantum field theories that exhibit Lifshitz scale symmetry provide a framework for studying low energy systems with an emergent dynamic scaling such as quantum critical points. Introducing supersymmetry to the Lifshitz algebra leads to a rich structure that is less constrained compared to that of relativistic supersymmetry. We construct supersymmetric Lifshitz quantum field theories and study their renormalization properties and RG flows. We show that models of Lifshitz supersymmetry that possess a holomorphic structure realize lines of quantum exact Lifshitz fixed points for various choices of spacetime dimensions and marginal supersymmetric interactions. The presented results are based on two papers.

String theory on AdS3xS3xT4 with one unit of NSNS flux has been recently argued to be dual to the symmetric product orbifold of T^4. The duality has been extended to the case of generic NSNS background flux. I will consider the bosonic version of this duality and show how to match null-vector constraints on three-point functions. I will explain how some three-point functions can be explicitly derived and matched on the two sides of the duality. This amounts to one of the very first holographic matches of non-protected AdS3/CFT2 correlators.

Conventionally, the main focus for the cosmic evolution of our universe has been on descriptions in terms of particles: dark matter (DM) as massive particle, and dark radiation, if existing at all, in the form of massless or very light particle. In this talk, I will discuss a scenario where conformal field theory (CFT) plays a crucial role in cosmology, especially production of naturally light dark matter. When the Standard Model (SM) couples to a sector of CFT, I will argue that in the regime where only the SM sector gets reheated, the energy density of the CFT sector is populated via energy injection from the SM (conformal freeze-in) and can be reliably computed. Such CFT energy density, redshifting like a radiation, will not account for DM unless somehow a mass gap is generated in the CFT. Remarkably, such a gap scale is dynamically generated due to phase transitions of SM: electroweak and QCD. In this way, DM energy today is produced in the early universe when it is not in gapped particle state, but a CFT state. Moreover, DM mass scale consistent with observed relic density and other observational constraints (mostly bullet cluster and warm dark matter bounds) turns out to be less than MeV. Therefore, conformal freeze-in provides a framework for naturally light DM.

The EHT Collaboration has recently published images of the supermassive black hole in M87. The images are dominated by a bright ring-like structure with an angular brightness asymmetry. While the diameter of this ring is resolved by the EHT, its thickness and detailed substructure are not. General relativity predicts that within this image lies a thin “photon ring,” composed of an infinite sequence of bright self-similar subrings. I will discuss the theoretical aspects of these general features of astrophysical black hole images, as well as the potential observability of the photon ring at extensions of the EHT.

Reading material:

arXiv:1907.04329, arXiv:1906.11242, arXiv:1905.11406

In this talk, I will discuss the idea that the exact one-loop free energy of the static patch of D-dimensional de Sitter space can be computed as a simple integral transform of an SO(1;D) bulk character corrected by an SO(1; D-2) edge character, for fields of arbitrary mass and spin. The bulk character captures the particle content of the theory and counts quasinormal modes in the bulk. The edge character counts edge modes on the horizon. I will also show the application of this formalism in 4D and 3D dS Vasiliev gravity. In the 4D case, after summing over spins, there is a huge cancellation between the bulk and edge characters, leaving the character of a scalar living in three dimensions. In the 3D case, I will discuss its relation with Chern Simons theory.

It is currently not well understood whether the holographic principle can be applied to asymptotically flat space-times. This talk will consider a flat limit of AdS/CFT that leads to a formula relating S-matrix amplitudes in flat space and conformal correlators in AdS/CFT. I will explain how to use the formula to compute S-matrices in simple examples, and I will discuss how to recast flat space physics concepts in the language of conformal field theory and holography. I will also discuss IR divergences and the construction of an IR finite S-matrix using AdS/CFT.

When absorbing boundary conditions are used to evaporate a black hole in AdS/CFT, we show that there is a phase transition in the location of the quantum Ryu-Takayanagi surface, at precisely the Page time. The new RT surface lies slightly inside the event horizon, at an infalling time approximately one scrambling time in the past. We can immediately derive the Page curve, using the Ryu-Takayanagi formula, and the Hayden-Preskill decoding criterion, using entanglement wedge reconstruction. Becausepart of the interior is now encoded in the early Hawking radiation, the decreasing entanglement entropy of the black hole is exactly consistent with the semiclassical bulk entanglement of the late-time Hawking modes, despite the absence of a firewall. By studying the entanglement wedge of highly mixed states, we can understand the state dependence of the interior reconstructions. Directly after the Page time, interior operators can only be reconstructed from the Hawking radiation if the initial state of the black hole is known. As the black hole continues to evaporate, reconstructions become possible that simultaneously work for a large class of initial states. This state dependence provides the mechanism by which information that falls into the black hole eventually escapes in the Hawking radiation.

We perform high resolution simulations in a scenario where the Peccei-Quinn (PQ) symmetry is broken after inflation starting at the epoch before the PQ phase transition and ending at matter-radiation equality. We characterize the spectrum of primordial perturbations that are generated and comment on implications for efforts to detect axion dark matter (DM). We also measure the DM density at different simulated masses and argue that the correct DM density is obtained for an axion mass of 25.2 ± 11.0 µeV.

I will review some old ideas about the duality between matrix models and Liouville theory coupled to a (p,q) minimal model. In this approach t'Hooft diagrams of the matrix model are thought of as a discretization of a 2d surface. Fine-tuning of the coupling constant leads to divergence of the perturbative expansion. In this limit dense t'Hooft diagrams dominate and become a good approximation of a smooth 2d surface.

Reading material:

hep-th/9306153; hep-th/9304011; Seiberg, "Notes on quantum Liouville theory and quantum gravity"; Lecture notes by Zamolodchikov brothers http://qft.itp.ac.ru/ZZ.pdf

The asymptotic symmetry algebra of asymptotically flat spacetimes implies an infinity of conserved charges for 4D scattering which can be neatly recast as 2D conformal Ward identities. We cover recent progress on the proposed 4D/2D dictionary starting from the conformally soft modes that appear as currents and extending our map to a basis for finite energy scattering states.

We study the effect of ZZ instantons in c = 1 string theory, and demonstrate that they give rise to non-perturbative corrections to closed string scattering amplitudes that do not saturate unitarity within the closed string sector. Beyond the leading non-perturbative order, logarithmic divergences are canceled between worldsheet diagrams of different topologies, due to the Fischler-Susskind-Polchinski mechanism. These results also allow us to propose the exact non-perturbative matrix model dual of c=1 string theory.

**Registration for each event is free, but required. Please click on the registration link below for each date, as it becomes available.**Talk #1: Machine Learning Techniques for Many-Body Quantum SystemsIn this introductory seminar I will cover the main machine learning techniques so-far adopted to study interacting quantum systems. I will first introduce the concept of neural-network quantum states [1], a representation of the many-body wave-function based on artificial neural networks. Theoretical aspects of these representations, including the problem of including symmetries, and their entanglement capacity will be discussed. Then, I will show how neural-network quantum states can be used in a variety of applications. Examples will be given for data-driven, experimental analysis in the context of quantum state tomography [2]. I will also show how these states can be used in variational applications to theoretically study the physical properties of interacting many-body matter, highlighting recent applications to frustrated magnetism [3] and fermionic systems [4].[1] Carleo, and Troyer - Science 355, 602 (2017); [2] Torlai, et al. - Nature Physics 14, 447 (2018); [3] Choo, et al. - arXiv:1903.06713 (2019); [4] Pfau, et al. - arXiv:1909.02487 (2019).Talk #2: Autoregressive Simulation of Many-body Quantum SystemsUnderstanding phenomena in systems of many interacting quantum particles, known as quantum many-body systems, is one of the most sought-after objectives in contemporary physics research. The challenge of simulating such systems lies in the extensive resources required for exactly modeling quantum wave-functions, which grows exponentially with the number of particles. Recently, neural networks were demonstrated to be a promising approximation method of quantum wave functions. However, thus far, this approach was mostly focused on more traditional architectures such as Restricted Boltzmann Machines and small fully-connected networks. In this talk, we propose a method for scaling this approach to support large modern architecture. Though significantly more expressive, such architectures do not lend themselves to the conventional methods for employing neural networks for simulating quantum systems. A key part of the simulation is to sample according to the underlying distribution of particle configurations. Current methods rely on Markov-Chain Monte-Carlo sampling, which is too expensive for use with modern architectures, effectively limiting their usable size and capacity. Inspired by recent generative models, we propose a specialized deep convolutional architecture that supports efficient and exact sampling, completely circumventing the need for Markov Chain sampling. We demonstrate our approach can obtain accurate results on larger system sizes than those currently accessible to other neural-network representation of quantum states.

Functional methods, in particular efficient reorganization of the one-loop effective action, have recently made a reappearance in simplifying the problem of computing matching and running effects in Lorentz-invariant effective field theories (EFTs) such as the Standard Model Effective Field Theory. This has lead to the appearance of universal one-loop effective actions, where such effects are now known in closed form for arbitrary field-content. These insights have not yet been brought to bear on modern kinematic EFTs such as heavy quark (HQET) and soft-collinear effective theory despite their greater focus on precision and the inclusion of higher-order effects. I will present some first steps in developing functional one-step matching formulae for EFTs where Lorentz symmetry is broken (or at least obscured) using HQET as my focus but also commenting on more complicated multi-mode EFTs as well.

We review some infinite dimensional symmetries that appear in dimensionally reduced classical general relativity. Reducing from d=4 to d=2 gives a two dimensional nonlinear sigma model with an infinite dimensional affine Kac-Moody symmetry called the Geroch group. Further reducing to d=1 (along a null Kill vector) enhances the Geroch group to a mysterious "hyperbolic Kac-Moody" symmetry.Further reading:

[1] P. Breitenlohner and D. Maison, "On the Geroch group," Ann. Inst. H. Poincare, 46, 215 (1987)

[2] H. Nicolai, "Two-dimensional gravities and supergravities as integrable systems," in “Schladming 1991, Proceedings, Recent aspects of quantum fields,” 231, and Hamburg DESY 91-038

[3] H. Lu, M. Perry, and C. Pope, ArXiv:0711.0400 and ArXiv:0712.0615

Recently, an exact AdS3/CFT2 duality was proposed. String theory on AdS3xS3xT4 with one unit of pure NS-NS background flux was conjectured to be dual to the symmetric product orbifold of T4. This is established at the level of the full spectrum of the CFT. In this talk I will report on the matching of sphere correlation functions. This involves crucially the so-called spectrally flowed representations. The moduli space integral of n-point functions for n>3 is argued to localise to a finite sum. I will also discuss the corresponding classical solution of the SL(2,R) WZW model and show that their on-shell action precisely reproduce the correlation functions in the symmetric product orbifold as calculated by path integral methods.

I will discuss time-dependent probes of the renormalization group, and derive new constraints that govern the spread of local operators in holographic theories. The same methods lead to sum rules for inflationary correlators, relating observables, like the speed of sound during inflation, to properties of the UV theory.

We consider supersymmetric twist and omega deformation of a type IIB brane setup involving N D3 and K D5 branes. In the large N limit, this leads to a holographic duality between two topological/holomorphic theories. We compute certain operator algebras from both sides of this topological holographic duality and find the result consistent with the claimed duality. The algebra we compute is the Yangian of gl_K, which is the symmetry algebra of an integrable spin chain. In addition, the instance of topological holography that we find is an example supporting Costello's proposal relating holography and Koszul duality.

We analyze modular invariance drawing inspiration from tauberian

theorems. Given a modular invariant partition function with a positive

spectral density, we derive lower and upper bounds on the number of

operators within a given energy interval. They are most revealing at high

energies. In this limit we rigorously derive the Cardy formula for the

microcanonical entropy together with optimal error estimates for various

widths of the averaging energy shell. Finally, we identify a new universal

contribution to the microcanonical entropy controlled by the central

charge and the width of the shell.

NOTE: LUNCH WILL BE HELD AT 12:00 PM IN THE SPACE NEXT TO THE PCTS SEMINAR ROOM.I will describe our continuing work for extracting the most of the LIGO-VIRGO data. In this talk, I will discuss the process that was used to characterize the impact of non-Gaussian phenomena (so called 'Glitches') I will then discuss the process that exploited the found properties in order to rank candidates based on one detector alone. I will then discuss how these candidates are then verified using very little information in the less sensitive detector. Using this, we found two new events. One (GW170817A) is the highest mass event reported to date. The other (GWC170402) was also very interesting, as there are some solid signs for the expression of higher modes, but a full coherent GR solution that explains the signal is still lacking. Last, I will discuss the implications of this method for the future analysis of the ongoing third observing run of the LIGO-VIRGO data.

The SYK Model was originally introduced as a random matrix model for the nuclear interaction that also describes the exponential rise of the spectral density known as the Bethe formula. Exactly this behavior is the hallmark of the Schwarzian action, the low energy limit of the SYK model, which is the main reason for the excitement this model has brought to the field of Quantum Gravity. Another phenomenon in chaotic many-body quantum systems is the existence of collective excitations. Remarkably, they are present in the Maldacena-Qi model of two SYK models coupled by a spin-spin interaction, which describes a phase transition between two black holes and a thermal phase. The collective state is the ground state which is close to a Thermo-Field Double state. We find that for systems that can be studied numerically, the wave functions of the ground state show substantial deviations from the Thermo-Field Double state, which suggests a non-uniform convergence to this state in the limit of a large number of particles. The main topic of this talk is the discussion of the thermodynamical and spectral properties of the Maldacena-Qi Model. We find a transition from Poisson statistics in the tail of the the spectrum to RMT statistics at higher energies, when we separate the Hamiltonian according to the spin mod 4 symmetry. We relate this order-chaos transition to the Hawking-Page phase transition.

The Born-Infeld model is an effective field theory of central importance describing the low-energy dynamics of massless gauge bosons on the world-volume of D-branes. Though it is in many ways an exceptional model of nonlinear electrodynamics, several aspects of the physics of the Born-Infeld model remain mysterious. In this talk I will explain how aspects of the model, obscured in the traditional formulation of Lagrangian field theory, are clarified by directly studying the on-shell S-matrix. In particular in 3+1-dimensions, classical Born-Infeld has an electromagnetic duality symmetry which manifests in tree-level scattering amplitudes as the conservation of a chiral charge. Whether this conservation law can be preserved under perturbative quantization is presently unknown. Using modern scattering amplitudes techniques, we have initiated a study of the S-matrix of Born-Infeld at one-loop. I will describe how generalized unitarity together with supersymmetric decomposition can be used to explicitly calculate infinite classes of one-loop amplitudes, and explain how the results are consistent with the existence of a quantum electromagnetic duality.

This talk will follow the discussions found in https://arxiv.org/abs/1711.04773 and https://arxiv.org/abs/1902.04082. We will discuss the cosmological implications of the Co-Decaying Dark Matter Model--a recently proposed mechanism for depleting the density of dark matter through the decay of nearly degenerate particles. This model generically predicts the existence of an Early Matter Dominated phase of universe evolution. We will show that this phase promotes sub-structure growth and solar mass primordial black holes.

The physics of systems with quenched random disorder reveals behavior qualitatively different from that found in systems with translational symmetry, continuous or discrete. The seminal work by Anderson over six decades back [1] established the phenomenon of electron localization in a model of non-interacting electrons and showed the existence of a metal-insulator (extended-localized) transition in three dimensions. Since then, a host of interesting phenomena have been uncovered, exploring e.g., the role of system dimensionality, the impact of breaking time-reversal and other symmetries, the influence of electron-electron interactions, and the effects of rare fluctuations.In this talk I will describe some of these through illustrative examples we have explored in the past several decades, using platforms where semiconductors act as the vacuum. I will discuss in particular (i) magnetic behavior of doped semiconductors below and above the insulator-metal transition [2-4], (ii) magnetism in diluted magnetic semiconductors at low electron density [5,6], and, if time permits, (iii) many-body electron localization in two dimensions in the quantum Hall regime [7.8].[1] P. W. Anderson, Physical Review **109**, 1492 (1958).

[2] R. N. Bhatt and P. A. Lee, Physical Review Letters** 48**, 344 (1982).

[3] M. Milovanovic, S. Sachdev and R. N. Bhatt, Physical Review Letters **63**, 82 (1989).

[4] R. N. Bhatt and D. S. Fisher, Physical Review Letters **68**, 3072 (1992).

[5] Xin Wan and R. N. Bhatt, International Journal of Modern Physics C **10**, 1459 (2000).

[6] Mona Berciu and R. N. Bhatt, Physical Review Letters **87**, 107203 (2001).

[7] Scott D. Geraedts and R. N. Bhatt, Physical Review B **95**, 054303 (2017).

[8] Akshay Krishna, Matteo Ippoliti and R. N. Bhatt, Physical Review B **89**, 041111(R) (2019); Physical Review B **100**, 054202 (2019).

Attendance is free, but space is limited, so please register! **Speakers:**

- Sheperd Doeleman
- Robbert Dijkgraaf
- Wendy Freedman
- Gabriela Gonzalez
- Theodore Jacobson
- Sergiu Klainerman
- Nergis Mavalvala
- Robert Myers
- Malcolm Perry
- Andrew Strominger
- Neil Turok
- William Unruh

The Event Horizon Telescope (EHT) is a Very Long Baseline Interferometry (VLBI) array operating at the shortest possible wavelengths, which can resolve the event horizons of the nearest supermassive black holes. Observing at mm radio wavelengths enables detection of photons that originate from deep within the gravitational potential well of the black hole, and travel unimpeded to telescopes on the Earth. The primary goal of the EHT is to resolve and image the predicted ring of emission formed by the photon orbit of a black hole and to eventually track dynamics of matter as it orbits close to the event horizon. A sustained program of improvements to VLBI instrumentation and the addition of new sites through an international collaborative effort led to Global observations in April 2017: the first campaign with the potential for horizon imaging. After 1.5 years of data reduction and analysis we report success: we have imaged a black hole. The resulting image is an irregular but clear bright ring, whose size and shape agree closely with the expected lensed photon orbit of a 6.5 billion solar mass black hole. This talk will cover the project and first results as well as future directions for a next-generation instrument that is aimed at real-time black hole video.

We are living in the golden era of gravitational research, realizing Einstein’s vision that by studying the geometry of space and time we can determine the origin, composition, and fate of the Universe. Cutting-edge technology has opened up many new windows in science, from the detection of the remnants of the Big Bang and gravitational waves to the image of a supermassive black hole. Yet, deep questions remain about the dark matter, dark energy, and the nature of quantum space-time.

**Speakers:**

- Sheperd Doeleman
- Robbert Dijkgraaf
- Wendy Freedman
- Gabriela Gonzalez
- Theodore Jacobson
- Sergiu Klainerman
- Nergis Mavalvala
- Robert Myers
- Malcolm Perry
- Andrew Strominger
- Neil Turok
- William Unruh

I will present my recent results on the behavior of solutions to the Klein-Gordon equation on the interior of Reissner-Nordstöm-AdS and Kerr-AdS. Despite the very slow logarithmic decay in the exterior, I show that linear waves arising from smooth data with Dirichlet boundary conditions at infinity remain bounded on the Cauchy horizon for Reissner-Nordström-AdS. For Kerr-AdS, however, the situation is far more delicate: Depending on the Diophantine properties of the ratio of the black hole parameters, linear waves blow up or remain bounded at the Cauchy horizon of Kerr-AdS.

I will explain how the S-matrix Bootstrap for massless particles can be used to constrain the space of Effective Field Theories (EFT). In particular, I will discuss the S-matrix bootstrap for massless particles in unitary, relativistic two dimensional quantum field theories. In the context of flux tube physics, this allows us to constrain several terms in the S-matrix low energy expansion or -- equivalently -- on Wilson coefficients of several irrelevant operators showing up in the flux tube effective action. The S-matrices living at the boundary of the allowed space exhibit an intricate pattern of resonances with one sharper resonance whose quantum numbers, mass and width are precisely those of the world-sheet axion previously proposed. Finally, I will present work in progress on pion scattering amplitudes and the chiral Lagrangian. The general method should be extendable to other massless S-matrices including gauge and gravity theories.

One generic scenario for the dark matter of our universe is that it resides in a hidden sector: it talks to other dark fields more strongly than it talks to the Standard Model. I'll discuss some minimal cosmological origin scenarios for this class of models and explore their consequences for the observability of dark states today. Some results of interest include simple, WIMP-y models of dark matter with parametrically novel behavior.

Phosphorus atoms qubits in silicon have demonstrated extremely long (up to 35 s) coherence times with >99.9% fidelity in the highly manufacturable material silicon. Their small size, combined with the magnetically quiet environment of isotopically pure silicon, make them analogous to ion trap qubits but in a scalable solid-state system. One of the long-term challenges for semiconductor qubits is to understand, and control, the local electromagnetic environment of the qubit down to sub 10nm length scales. Scanning probe techniques, combined with molecular beam epitaxy allow us to engineer fully crystalline devices at the atomic scale and directly probe the qubit wave function with exquisite precision. We will discuss the progress and vision for this approach.

We describe the coupling of holomorphic Chern-Simons theory at large N with Kodaira-Spencer gravity. This gives a complete description of open-closed string field theory in the topological B-model. We explain an anomaly cancellation mechanism at all loops in perturbation theory in this model. At one loop this anomaly cancellation is analogous to the Green-Schwarz mechanism. This is joint work with Kevin Costello.

Because of the Black-Hole Information Paradox, and the singularity, many physicists believed that GR must be modified to incorporate quantum effects, and that such modifications may affect black-hole spacetimes. The additional near-horizon structure might modify the boundary conditions for incoming gravitational waves, and lead to gravitational wave echoes. These echoes will then become the "smoking gun" of modifications to relativity. Therefore parametrizing gravitational echoes and searching for them will be an important way to quantify how "black" the black holes really are. In this talk, I will talk about the theoretic formulation of gravitational wave echoes, and point out the current issues associated with this idea.

I will describe my work, all joint with D. Gaiotto and some also joint with E. Witten, to understand the homotopy type of the space of (1+1)d N=(0,1) SQFTs --- what a condensed matter theorist would call "phases" of SQFTs. Our motivating hypothesis (due in large part to Stolz and Teichner) is that this space models the spectrum called "topological modular forms". Our work includes many nontrivial checks of this hypothesis. First, the hypothesis implies constraints on the possible values of elliptic genera, and suggests (but does not imply) the existence of holomorphic SCFTs saturating these constraints; we have succeeded in constructing such SCFTs in low central charge. Second, the hypothesis implies the existence of torsion-valued "secondary invariants" beyond the elliptic genus that protect SQFTs from admitting deformations that spontaneously break supersymmetry. I will explain such an invariant in terms of holomorphic anomalies and mock modularity.

**Registration for each event is free, but required. Please click on the registration link below for each date, as it becomes available. ****Register here: **

https://docs.google.com/forms/d/e/1FAIpQLScD1ZGB17mwhZ3cvyvs8vEqArGJknmcn_udUgL4tJm4DatmUA/viewform Abstract Talk #1: The initial breakthroughs of deep learning came in the form of predictive tasks such as image classification, where discriminative models were trained with supervised learning algorithms. More recently, there have been exciting developments for generative models trained with unsupervised learning algorithms. Generative models approximate the distribution of the data and open up a wider range of possible applications. Generative Adversarial Networks (GANs) are the most well known of these models; however, they have drawbacks. I will describe an alternative approach called normalizing flows and discuss them in the context of three physics problems: effective field theory measurements at the LHC, lattice quantum chromodynamics, and modeling the density matrix of a quantum system.Abstract Talk #2: String theory is a theory of quantum gravity that has had strong impacts on theoretical physics and mathematics. In this talk I will describe ways in which deep learning may lead to progress in string theory, with a special focus on broad applications in the string theory landscape. Known properties of the landscape and its relation to computational complexity will be briefly discussed, including ways in which the structure of the theory allows for the avoidance of worst-case complexity; for instance, networks of extra-dimensional spaces connected by topology changing transitions can aid in solving physically relevant Diophantine problems. The talk will focus on two types of problems in string theory. First, generative models will be discussed as a means for approximating statistical predictions, which are crucial given the large landscape of solutions. As a simple application, a conditional Wasserstein DCGAN will be used to learn random matrix approximations to Kahler metrics on Kahler moduli space, which are relevant for the physics of axion-like particles. Second, we will discuss multi-task search problems that arise in the landscape. A reinforcement learning A3C agent will be utilized to solve a multi-task problem in type IIA compactifications on a toroidal orbifold. Significant improvement over a random walker is achieved, a known human strategy is learned by the agent, but an RL-discovered strategy performs about twice as well.

Motivated by theories of neutral naturalness, I will argue that Mirror Stars are a generic possibility in any hidden sector with analogues of Standard Model electromagnetism and nuclear physics. I will show that if there exists a tiny kinetic mixing between the dark and SM photon, Mirror Stars capture SM matter from the interstellar medium, which accumulates in the Mirror Star core. This leads to a spectacular and distinctive signature that could be discovered in optical and X-ray searches.

Suggested reading:

Marc Mars, Present Status of the Penrose Inequality, arXiv:0906.5566

Netta Engelhardt and Gary Horowitz, A Holographic Argument for the Penrose Inequality in AdS, arXiv:1903.00555

Quantum Penrose Inequality, arXiv:1908.02755

The Wilsonian paradigm suggests universality of quantum field theory in the infrared. Interestingly, it also suggests universality of quantum mechanics (d=1 quantum field theory) in the *ultraviolet*. This suggests a study of the landscape of the infrared and the robustness of the ultraviolet. I will introduce and solve an infinite class of integrable deformations to quantum mechanics, focusing on a particular deformation inspired by the T-Tbar deformation of two-dimensional quantum field theory. In the context of holography, I will show how these deformations modify Jackiw-Teitelboim gravity in AdS_2. I will also present an equivalent description of the T-Tbar deformation in terms of coupling to worldline gravity. Applications to the Schwarzian theory and SYK will be discussed.

We are now experiencing a revolution in optical technologies, where one can print and control massive optical circuits, on a microelectronic chip. This revolution is enabling a whole range of applications that are in need for scalable optical technologies and it is opening the door to areas that only a decade ago were unimaginable.In the past decade, the photonic community witnessed a complete transformation of optics. We went from being able to miniaturize a handful of devices to being able to define and control the flow of light using thousands of monolithically integrated optical components – all on a silicon chip. The main drive for silicon photonics is the ability to transmit and manipulate ultra high bandwidth with low power dissipation. Today there are hundreds of products being developed and commercialized towards this goal.The field of silicon photonics is rapidly evolving and is now enabling completely new applications, ranging from Lidar to biomedical devices. This is partly due to the development of novel chip-scale technologies, novel devices and novel materials compatible with silicon photonics. Many of these technologies and devices can manipulate light across the whole VIS, IR and the Mid IR spectrum. I will discuss these emerging applications, as well as the advancement brought by these novel devices and materials.The key challenges of the field relate to the scalability of the systems in bandwidth, size and power. Some of these challenges are fundamental and require innovations that break traditional tradeoffs. Novel approaches for switching, modulating and amplifying light have emerged that can open the door to applications that rely on such scalable systems. I will describe the challenges of the field and some of the recent innovations that can potentially address these challenges.

The Kerr-Newman spacetime is the most general explicit black hole solution, and represents a stationary rotating charged black hole. Its stability to gravitational and electromagnetic perturbations has eluded a proof since the 80s in the black hole perturbation community. As put by Chandrasekhar, "the methods that have proved to be so successful in treating the gravitational perturbations of the Kerr spacetime do not seem to be applicable for treating the coupled electromagnetic-gravitational perturbations of the Kerr-Newman spacetime". He adds, "the principle obstacle is in finding separated equations".

Following the road map that mathematicians have taken in interpreting in physical space the known mode analysis, we will present a way to overcome "the apparent indissolubility of the coupling between the spin-1 and spin-2 fields in the perturbed spacetime". We will explain how the decomposition in modes, done to simplify the analysis of the equations, makes them unsolvable when electromagnetic and gravitational radiations interact. We instead generalize the Chandrasekhar transformation to Kerr-Newman in physical space and use it to obtain a quantitative proof of stability.

While the flat space two-body problem is integrable, the generally-relativistic one is not starting at the next-to-leading order.

In the appropriate classical limit, scattering amplitude-based techniques can yield the classical interaction of massive bodies to all orders in their velocities and to fixed order in the expansion in Newton's constant, that is a fixed order in the post-Minkowskian (relativistic weak-field) expansion.

In this talk we review an amplitudes-based framework for such calculations and the derivation of the third order in the post-Minkowskian expansion for the conservative Hamiltonian of a compact spinless binary system. We also describe the scattering angle at this order as well as a first comparison with numerical GR.

There is currently a (possible) tension between various measurements of the Hubble expansion rate. I will give a recap of this issue, and describe how we use the Cosmic Microwave Background to infer the local expansion rate. I will explain what assumptions we usually make about the cosmological model in doing so, and what kinds of early-universe modifications could bring some of the different measurements better in line. I will talk about new measurements we are making in Chile to improve estimates of the Hubble constant from the CMB, and to test alternative models.

With the detection of GW170817 we have observed the first multi-messenger gravitational wave signal from two merging neutron stars. This signal carried a multitude of information about the underlying equation of state (EOS) of nuclear matter, which so far is not known for densities above nuclear saturation. In particular it is not known if exotic states or even a phase transition to quark matter can occur at densities so extreme that they cannot be probed by any ground-based experiment. I will show how the information carried in the gravitational wave signal of GW170817 can be used to constrain the EOS at densities above saturation and what we can learn about the possible existence of phase transitions.I will also comment on how we can improve on those limits with upcoming observations of the NICER mission.

In the second part of the talk,I will focus on yet to be observed electromagnetic precursor emission from neutron star mergers. These precursors have the potential to provide complementary insights into the properties of neutron stars, such as their spins, which cannot yet be reliably extracted from the gravitational wave signal. I will present preliminary results on the interaction of force-free magnetospheres in compact binaries and demonstrate how powerful electromagnetic flares can be launched for a wide variety of orbital parameters.

I will introduce a new discrete transformation in quantum field theory with Z2 1-form symmetry, with some applications to boson/fermion dualities in (2+1)d.

This is based on the work https://arxiv.org/abs/1909.07383with Shu-Heng Shao (IAS).

**Please Note:** This workshop is not open to the general public, but only to active researchers.This workshop will focus on quantum aspects of black holes, focusing on applying ideas from quantum information theory.This meeting is sponsored by the "It from Qubit"collaboration and is followed by the collaboration meeting in New York City.

Very light axions are a generic prediction of string compactifications. If cosmic strings associated with these axions were produced in the early universe, they quickly approach a so-called scaling solution, such that strings persist in the sky today. I will present some remarkable signals of such strings coupled to photons. In this string background, there is a model-independent polarization rotation of CMB photons equal to $\alpha_{em}$ up to a rational number. This manifests itself as a rotation of E-modes in the CMB polarization to B-modes. The current CMB experimental sensitivity to this rotation is about 1%, with many orders of magnitude improvement expected for future experiments. I will show how measuring the undetermined rational number may shed light on the quantization of electric charge in the standard model. These strings may also be visible in strongly lensed quasar systems.

**Please Note:** This workshop is not open to the general public, but only to active researchers.This workshop will focus on quantum aspects of black holes, focusing on applying ideas from quantum information theory.This meeting is sponsored by the "It from Qubit"collaboration and is followed by the collaboration meeting in New York City.

The National Academy has recently called for the US to adopt a strategy to produce fusion electricity from a compact pilot plant by mid-century. This approach requires innovations in technology (e.g. magnet systems and power handling systems) and innovations in physics. I will introduce the key issues that challenge the current program and recent theoretical and experimental progress. I will also discuss research at PPPL to develop optimal three dimensional magnetic configurations and low cost engineering solutions for their realization.

Every astrophysically realistic simulation needs accurate initial data and in this talk I will present methods to obtain such solutions for a variety of problems. In particular I will focus on a new initial data formulation to solve the full set of Einstein equations for spacetimes that contain a black hole under general conditions. As an application I will present nonaxisymmetric, self-gravitating tori in the presence of a black hole whose spin is tilted with respect to the angular momentum of the disk. The numerical implementation of these methods is done in the context of the Compact Object CALculator (COCAL) code whose purpose is to provide initial data for any general-relativistic system.

In the second part of this talk I will address two questions: First, how one can distinguish a binary black hole undergoing a merger from a binary neutron star if the individual compact companions have masses that fall inside the so-called mass gap of 3-5 solar masses? I will show that although the ringdown phase is indistinguishable from the perturbed Kerr spacetime, the inspiral phase can lead to measurable differences. Second, whether any of the known neutron stars that exhibit ergoregions are dynamically stable? If not, can we identify any dynamically stable ergostar? The answer to these questions will have consequences to the conjecture by Komissarov that a horizon is not necessary for the energy creation of a relativistic jet.

The Cosmic Microwave Background is a unique tool to investigate the early universe and the largest structures observable in the sky. The main CMB observables such as anisotropies, polarization state and Sunyaev Zel’Dovich effect can give us a detailed view of the cosmos providing stringent constraints to the parameters of our models. To extract the information encoded in the radiation we need extremely sensitive detectors and low noise readout. Transition edge sensors and superconducting quantum interference devices are the state of the art technology for this purpose. The implementation on present and future balloon borne experiments will be introduced and discussed as well as the next generation ground experiments.

The Andromeda galaxy is the closest spiral galaxy to us. It harbors a massive dark matter halo which may span up to ∼600 kpc across and comprises ∼90% of the galaxy’s total mass. This halo size translates into a large diameter of 42 degrees on the sky for an M31–Milky Way distance of 785 kpc, but its presumably low surface brightness makes it challenging to detect with gamma-ray telescopes. Using data from the Fermi Large Area Telescope, we make a detailed study of the gamma-ray emission between 1-100 GeV towards Andromeda's outer halo, and perform an in-depth analysis of the systematic uncertainties related to the observations. In this talk, I will discuss these results and implications for dark matter.

We will prove a conjecture [1] on upper bound of asymptotic gap in dimension in unitary compact 2D CFT, proving it to be 1 using a "extremal" function [2]. The notion of asymptotic gap can be generalized to (h, \bar{h}) plane [3]. We will discuss how the extremal function used in [2] can be put into a bigger (natural) framework of an extremal problem of entire function with certain exponential growth [4]. This facilitates a generalization of construction of optimal function (within the class of Bandlimited function) and hence the optimal gap on (h, \bar{h}) plane. Reading material:[1] Baur Mukhametzhanov, Alexander Zhiboedov, *Modular Invariance, Tauberian Theorems, and Microcanonical Entropy*, arXiv: 1904.06359 [hep-th][2] Shouvik Ganguly, SP, *Bounds on density of states and spectral gap in CFT_2*, arXiv: 1905.12636 [hep-th] (in particular section 4)[3] SP, Zhengdi Sun,* Tauberian-Cardy formula with spin*, arXiv: 1910.07727 [hep-th]

[4] D. V. Gorbachev, * Extremum Problems for Entire Functions of Exponential Spherical Type*, Mathematical Notes, Vol 68, N0. 2, 2000

I will mostly be focussing on the extremal problem. More reading material on application of Tauberian theorem can be found in:

1. D. Pappadopulo, S. Rychkov, J. Espin, and R. Rattazzi, Operator product expansion convergence in conformal field theory, Physical Review D 86 no. 10, (2012) 105043.2. J. Qiao and S. Rychkov, A tauberian theorem for the conformal bootstrap, JHEP 12 (2017) 119, arXiv:1709.00008 [hep-th].3. B. Mukhametzhanov and A. Zhiboedov, Analytic euclidean bootstrap, arXiv preprint arXiv:1808.03212 (2018).4. SP, Bound on asymptotics of magnitude of three point coefficients in 2D CFT, arXiv:1906.11223 [hep-th].5. Appendix C of D. Das, S. Datta, and SP, Charged structure constants from modularity, JHEP 11 (2017) 183, arXiv:1706.04612 [hep-th].

The immune system is composed of a large number of heterogenous interacting components that collectively recognize and clear pathogens. To cover the high-dimensional molecular space of all possible threats, including those that have never been seen before, the adaptive immune system is endowed with a wide variety of receptor proteins, which are created by random cutting-and-pasting of the DNA in each cell. I will show how the rules of that process can be statistically learned from high-throughput sequencing data, and can be used to calculate its entropy and to predict accurately receptor overlap between individuals. I will then present a theoretical framework for thinking about optimal designs for enacting and encoding immune memory through the self-organisation of the repertoire.

I will discuss topological classification of gapped many-body Hamiltonians and their ground states in dimension d. In general, the problem is too hard as it includes diverse phenomena such as degenerate ground states on the torus, anyons, and fractons. There is, however, hope to fully understand short-range entangled, or "invertible" systems, which do not have the aforementioned features but may possess gapless edge modes. In the case of non-interacting fermions, the topological classification is based on K-theory. I will argue that general invertible systems are described by some homotopy spectrum (or equivalently, generalized cohomology theory). However, the exact answer is not yet known.

In its high-luminosity phase, the CERN Large Hadron Collider will produce x10 more data, while the computing power for data processing will not scale accordingly. Particle physicists need novel solutions to accomplish the scientific mission of the LHC. Deep Learning has the potential to be the game changer that could solve the problem. In this seminar, I will describe the main conceptual and technological problems that need to be addressed by 2026 and where Deep Learning could play a major role.

LOCATION:Jadwin Hall Room 303 COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200121T190000Z DTEND:20200121T203000Z SUMMARY:PCTS Special Seminar, "Physics and Energy" (Robert L. Jaffe, MIT) DESCRIPTION:Energy is a central concept in physics. Because energy is conserved, it is possible to understand the behavior of complex systems by tracing the flow of energy through them. On the other hand, we humans “consume” energy, degrading it into less useful forms, as it powers modern societies. Providing energy for the world to use in a sustainable fashion is a major, perhaps existential challenge for humankind in the 21st century. The scale and scope of the problem is enormous. The implications for Earth and human societies are profound.

Economic considerations and political decisions will be central to any attempt to address this energy challenge. However, decisions made in the absence of good scientific understanding have the potential to waste vast amounts of effort and resources and to adversely affect countless lives and large ecosystems. A clear understanding of the science of energy is essential for specialists and non-specialists alike. Physicists and our universities have an opportunity, even a responsibility to provide this understanding.

In response to this challenge, Washington Taylor and I developed a physics course for MIT undergraduates and an associated textbook — *“The Physics of Energy”* –– that focus on the sources and uses of energy, and on energy systems and the externalities associated with energy use, including climate change. After setting out the nature of the problem, I will describe the motivation for and structure of an energy-centered university physics course for students with a strong science and math background, illustrate the topics it covers, and relate some of the insights that we uncovered along the way.

Compositeness is an elegant way to address the hierarchy problem. In this talk, under broad assumption of partial compositeness and Higgs doublet as the pseudo-Nambu-Goldstone bosons, I will discuss about phenomenology of the spin-1 resonances and the top partners in CHMs and the relevance of their strong interactions in the searches at the LHC. I will also discuss about the strong multi-pole interaction as the target scenario for the precision measurement in the di-boson processes at the HL-LHC. Finally, I will briefly discuss about the universal relationship between the Higgs couplings predicted by the non-linearity and their phenomenological relevance in the future lepton colliders.

LOCATION:Jadwin Hall Room 303 COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200128T210000Z DTEND:20200128T210000Z SUMMARY:Pheno & Vino Seminar, "Soft Signals at the LHC" (Simon Knapen, Institute for Advanced Study) DESCRIPTION:The LHC is both a Higgs and B-factory, and for both particles it will likely deliver the largest data set we will see in our lifetimes. I will discuss a few examples on how we can leverage this to search for beyond the Standard Model physics. Some ideas can be implemented now, while others rely on the phase II upgrade.

LOCATION:Princeton University Jadwin Hall Room 303 COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200203T150000Z DTEND:20200203T190000Z SUMMARY:Dark Matter at Jadwin: An Informal Mini- Symposium DESCRIPTION: LOCATION: COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200203T173000Z DTEND:20200203T173000Z SUMMARY:Gravity Initiative Lunch, "Finite Size Effects on the Self-Force" (Klaountia Pasmatsiou, Case Western Reserve University) DESCRIPTION:Electromagnetic and linear gravitational radiation do not solely propagate on the null cone in 3+1 dimensions in curved spacetimes, contrary to their well-known behavior in flat spacetime. Their additional propagation inside the null cone is known as the tail effect. In the first part of the talk, I will present new results for the tail-induced electromagnetic and gravitational self-force for a test particle in orbit around a central body. This test particle will produce a signal whose tail will interact with its future worldline, thus producing a tail-induced self-force. I will show that the self force can serve as a probe of the internal structure of the central object, with possible future implications for neutron star-black hole mergers. During the second part of the talk, I will present preliminary results towards the development of the "tail electrodynamics" and the propagation of tail radiation in a weakly curved spacetime.

LOCATION:Jadwin Hall, Princeton Gravity Initiative, 4th Floor COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200203T193000Z DTEND:20200203T193000Z SUMMARY:High Energy Theory Seminar, "X-ray Search for Axions from Nearby Isolated Neutron Stars" (Ben Safdi, University of Michigan) DESCRIPTION:Axions may be produced thermally inside the cores of neutron stars (NSs), escape the stars due to their weak interactions with matter, and subsequently convert into X-rays in the magnetic fields surrounding the NSs. I will describe a hard X-ray search from 2 - 8 keV for X-rays arising from this emission mechanism from the nearby Magnificent Seven isolated NSs using archival XMM-Newton and Chandra data. This search leads to the strongest limits to-date on the product of the axion-photon and axion-nucleon couplings for axion masses below ~1e−4 eV. Moreover, I will show that an observed excess of hard X-rays from the Magnificent Seven may arise from axions, and I will discuss near-term measurements to help rule out or confirm this possibility. LOCATION:Bloomberg Lecture Hall (IAS) COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200204T210000Z DTEND:20200204T210000Z SUMMARY:Pheno & Vino Seminar, "Dynamical Friction in a Fuzzy Dark Matter Universe" (Cara Giovanetti, Princeton University) DESCRIPTION:Fuzzy Dark Matter (FDM) is a model of dark matter consisting of an ultralight scalar whose quantum mechanical nature is manifest at kiloparsec scales. As such, an object moving through an FDM halo will experience a different drag force due to dynamical friction than an object passing through a classical dark matter halo. This effect is pronounced enough that it can be observed when measuring the infall times of satellites as they spiral in towards galaxy centers. In this talk I will explore the use of analytical theory and numerical simulations to determine the magnitude of this effect. I will also apply these results to different astrophysical systems and discuss the use of dynamical friction to support or rule out FDM as a dark matter candidate.

LOCATION:Jadwin Hall Room 303 COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200206T164500Z DTEND:20200206T164500Z SUMMARY:PCTS Seminar Series: Deep Learning for Physics, "Topic #1: Understanding Machine Learning via Exactly Solvable Statistical Physics Models; Topic #2: Dynamics of Generalization in Overparameterized Neural Networks" (Speaker #1: Lenka Zdeborova; Speaker #2: Andrew Saxe, Speaker #1: CEA Scalay and CNRS; Speaker #2: Oxford University) DESCRIPTION:Please Note: The seminars are not open to the general public, but only to active researchers.

Register here for this event:

https://docs.google.com/forms/d/e/1FAIpQLScJ-BUVgJod6NGrreI26pedg8wGEyPhh3WMDskE1hIac_Yp3Q/viewform

Abstract for talk #1: The affinity between statistical physics and machine learning has long history, this is reflected even in the machine learning terminology that is in part adopted from physics. I will describe the main lines of this long-lasting friendship in the context of current theoretical challenges and open questions about deep learning. Theoretical physics often proceeds in terms of solvable synthetic models, I will describe the related line of work on solvable models of simple feed-forward neural networks. I will highlight a path forward to capture the subtle interplay between the structure of the data, the architecture of the network, and the learning algorithm.

Abstract for talk #2: What interplay of dynamics, architecture, and data make good generalization possible in overparameterized neural networks? Approaches from statistical physics have shed light on this question by considering a variety of simple limiting cases. I will describe results emerging from two simple models: deep linear neural networks and nonlinear student-teacher networks. In these models, good generalization from limited data arises from aspects of training dynamics and initialization. Finally, I will briefly tour open problems facing practitioners that seem amenable to analysis with similar methods.

Each talk will be preceded with lunch at 11:45 am. The talks will be held from 12:25-1:30 pm and from 2:00 - 3:00 pm.

URL:http://pcts.princeton.edu/programs/current/deep-learning-for-physics-seminar-series/121 END:VEVENT BEGIN:VEVENT UID: DTSTART:20200207T184500Z DTEND:20200207T184500Z SUMMARY:High Energy Theory Seminar, "Three Avatars of Mock Modularity" (Atish Dabholkar, Abdus Salam ICTP, Trieste) DESCRIPTION:Mock theta functions were introduced by Ramanujan in his famous last letter to Hardy in 1920 but were properly understood only recently with the work of Zwegers in 2002. I will describe three manifestations of this apparently exotic mathematics in three important physical contexts of holography, topology and duality where mock modularity has come to play in important role.

In particular, I will derive a holomorphic anomaly equation for the indexed partition function of a two-dimensional CFT2 dual to AdS3 that counts the black hole degeneracies, and for Vafa-Witten partition function for twisted four dimensional N=4 super Yang-Mills theory on CP2 for the gauge group SO(3) that counts instantons. The holomorphic kernel of this equation is not modular but `mock modular’ and one obtains correct modular properties only after including certain `anomalous’ nonholomorphic boundary contributions. This phenomenon can be related to the holomorphic anomaly of the elliptic genus of a two-dimensional noncompact supersymmetric sigma model, and in a simpler context of quantum mechanics to the Atiyah-Patodi-Singer eta invariant.

Mock modularity is thus essential to exhibit modular symmetries expected from the AdS3/CFT2 holographic equivalence in quantum gravity and the S-duality symmetry of four-dimensional quantum gauge theories.

LOCATION:407 Jadwin Hall, 4th Floor, PCTS Seminar Room COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200210T173000Z DTEND:20200210T173000Z SUMMARY:Gravity Initiative Lunch, "Studying Neutron Stars with Gravitational Waves" (Katerina Chatziioannou, CCA) DESCRIPTION:Neutron stars, the most dense astrophysical bodies we know of, are at the heart of many interesting astrophysical phenomena from their birth in supernova explosions to their deaths in collisions with other dense objects. Even though we have been witnessing the births of neutron stars in the night (or even day!) sky for thousands of years, the collision of two neutron stars was detected for the first time only two years ago through gravitational waves.

In this talk I will discuss what insights the detected signal, GW170817, has offered about the properties of astrophysical neutron stars and how it compares to other recent probes of neutron star matter such as NICER. I will also discuss what we expect to discover in the next few years about the properties of matter that is more dense than the nuclei everyday atoms are made of.

LOCATION:Jadwin Hall, Princeton Gravity Initiative, 4th Floor COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200210T193000Z DTEND:20200210T193000Z SUMMARY:High Energy Theory Seminar, "An Effective Field Theory of Quantum Black Hole Horizons" (Walter Goldberger, Yale University) DESCRIPTION:I develop an effective theory which describes black holes with quantum mechanical horizons that is valid at scales long compared to the Schwarzschild radius but short compared to the lifetime of the black hole. The formalism allows one to calculate the quantum mechanical effects in scattering processes involving black hole asymptotic states. The EFT Wightman functions which describe Hawking radiation in the Unruh vacuum are not Planck suppressed and are actually enhanced relative to those in the Boulware vacuum, for which such radiation is absent. We elaborate on this point showing how the non-Planck suppressed effects of Hawking radiation cancel in classical observables. Applications to inelastic gravitational scattering of point particles off quantum black holes will be briefly discussed. LOCATION:Bloomberg Lecture Hall (IAS) COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200211T210000Z DTEND:20200211T210000Z SUMMARY:Pheno & Vino Seminar, "Direct Detection Searches for Fuzzy Dark Matter and Ultra Low Mass Axions at Princeton" (William Terrano, Princeton University) DESCRIPTION:I will discuss experimental prospects for directly detecting ultra-low-mass dark matter, including the interesting “Fuzzy” dark matter scenario. I will describe experiments which are ongoing here at Princeton, and the challenges associated with them. I will also present the results we have thus far, and the prospects for future improvements.

LOCATION:Princeton University Jadwin Hall Room 303 COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200213T210000Z DTEND:20200213T210000Z SUMMARY:Hamilton Colloquium Series, "The Physics of Collective Cell Migration" (Ricard Alert, Princeton University) DESCRIPTION:Cells in our body move in groups during development, wound healing, and tumor spreading. Bacterial cells also coordinate their motion to aggregate into biofilms, to feed cooperatively, and to form fruiting bodies. All these collective movements rely on physical mechanisms involving cell-generated propulsion forces and both mechanical and biochemical interactions between cells. In the first part of the talk, I will review how cell-cell interactions lead to the emergence of collective phenomena in migrating cell groups. These phenomena include internally-driven fluid-solid and wetting transitions, hydrodynamic instabilities, as well as the appearance of orientational order, spontaneous flows, and mechanical waves even in the absence of inertial effects. I will illustrate how the quest for understanding collective cell migration has stimulated the development of active-matter physics — a new branch of non-equilibrium soft-matter physics. In the second part of the talk, I will present our studies on colonies of the soil bacterium *Myxococcus xanthus*. When the elongated and motile bacterial cells are densely packed, they align with neighboring cells and form an active liquid crystal. I will show that topological defects of the nematic cell alignment lead to the formation of new layers of cells, which triggers the growth of fruiting bodies in the bacterial colony.

Reparametrization modes provide a way of describing universal physics of energy-momentum exchanges in CFTs. Drawing inspiration from effective field theory methods and the SYK model, I will argue that this perspective offers a useful computational and conceptual framework. For example, stress tensor contributions to conformal blocks can be systematically organized in terms of reparametrization mode exchanges, thus leading to a simple and efficient diagrammatic perturbation theory at large central charge. To illustrate this method, I will discuss some known stress tensor conformal blocks in various dimensions, and will also present a new result regarding the six-point "identity block" in 2d CFTs. I will also mention an application to thermal physics in higher dimensions and argue that the theory of reparametrization modes provides useful intuition for the physics underlying quantum chaos in Rindler space.

LOCATION:Bloomberg Lecture Hall (IAS) COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200217T130000Z DTEND:20200218T220000Z SUMMARY:PCTS Workshop Structure-Preserving Geometric Discretization of Physical Systems DESCRIPTION:Registration at: https://docs.google.com/forms/d/e/1FAIpQLSeHnBCTiEdc9ZqogazfBRc6nhFJKadRUiXwjdJyrBKhjGk2RQ/viewform

http://pcts.princeton.edu/programs/current/structure-preserving-geometric-discretization-of-physical-systems/119

Topics:

Structure-preserving algorithms, Geometric integration, Geometric particle-in-cell methods, Symmetries in lattice quantum field theories

Program Organizers:

Hong Qin, Clarence Rowley, Nathaniel Fisch, and Melvin Leok

Program Committee:

Joshua Burby, Nathaniel Fisch, Arieh Iserles, Melvin Leok, Philip Morrison, Hong Qin, Clarence Rowley, and Eric Sonnendrücker

Confirmed Speakers:

• Silas Beane (Univ. Washington)

• Josh Burby (LANL)

• Elena Celledoni (Norwegian Univ. Sci. & Tech.)

• Zohreh Davoudi (Univ. Maryland)

• Evan Gawlik (Univ. Hawaii)

• Alexander Glasser (Princeton)

• Shi Jin (Shanghai Jiaotong Univ.)

• Michael Kraus (IPP Max-Planck)

• Klas Modin (Chalmers)

• Yuan Shi (LLNL)

• Ari Stern (Washington Univ.)

• Tomasz Tyranowski (IPP Max-Planck)

• Jianyuan Xiao (Univ. Sci. & Tech. China)

Hot spots, or plasmoids, formed due to magnetic reconnection in thin current sheets are conjectured to power frequent bright X-ray and near-infrared flares from supermassive black holes, like Sgr A* in the center of our Galaxy. It is of yet unclear how, where, and when thin current sheets form in black hole accretion flows, and whether magnetic reconnection in such sheets is capable of producing highly energetic plasmoids. In this talk I will show general relativistic resistive magnetohydrodynamics models of magnetic reconnection and associated plasmoid formation in a wide range of accretion flows. I will show that plasmoids are a ubiquitous feature of accretion flows regardless of the magnetic field geometry and the spin of the black hole. The location of the current sheets, how frequently they form, and typical size of the largest plasmoids do depend strongly on the magnetic field geometry. In all cases we observe plasmoids forming close to the event horizon within 5 to 10 Schwarzschild radii, after which the they grow to macroscopic scales and advect along the jet boundary or into the disk. We determine the typical reconnection rate, the Ohmic heating, and the occurence of non-ideal electric fields responsible for particle acceleration. We also show that an explicit resistivity allows for converged numerical solutions, such that the electromagnetic energy density evolution and dissipation is independent of the grid resolution and numerical heating is negligible for the extreme resolutions we considered.

LOCATION:Jadwin Hall, Princeton Gravity Initiative, 4th Floor COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200218T210000Z DTEND:20200218T210000Z SUMMARY:Pheno & Vino Seminar, "Uncovering Dark Matter with Compact Objects and Automatic Differentiation" (Christoph Weigner, University of Amsterdam) DESCRIPTION:The nature of dark matter (DM) in the Universe remains one of the great open questions of particle astrophysics and cosmology today. The WIMP (weakly interacting massive particle) DM paradigm has fallen, leaving us with a wide range of possible DM models and signatures. New methods and ideas are required to efficiently progress. I will discuss ongoing searches for axion DM signatures using radio observations of neutron stars, and discuss the potential role of black holes and gravitational waves. I will furthermore demonstrate how machine learning technology like automatic differentiation and deep universal probabilistic programming can significantly improve the analysis of astrophysical data. As application I will present preliminary results for the analysis of strongly lensed images.

LOCATION:Jadwin Hall Room 303 COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200219T130000Z DTEND:20200219T230000Z SUMMARY:PCTS Workshop, "Large N Theories and Strings: Conformal, Confining, and Holographic" DESCRIPTION:**Organizers: Nathan Benjamin, Simone Giombi, Victor Gorbenko, Shota Komatsu, Silviu Pufu, Xinan Zhou**In recent years, there has been much interesting progress from disparate subfields of high energy physics, all under the unifying theme of theories with a large number of degrees of freedom. This includes strings in confining gauge theories, conformal field theories, quantum gravity, and the gauge/string dualities. The purpose of this workshop is to bring together experts in those fields to revisit and shed new lights on the original idea of theories of large N. **Please Note: This workshop is not open to the general public, but only to active researchers.**

**Organizers: Nathan Benjamin, Simone Giombi, Victor Gorbenko, Shota Komatsu, Silviu Pufu, Xinan Zhou**In recent years, there has been much interesting progress from disparate subfields of high energy physics, all under the unifying theme of theories with a large number of degrees of freedom. This includes strings in confining gauge theories, conformal field theories, quantum gravity, and the gauge/string dualities. The purpose of this workshop is to bring together experts in those fields to revisit and shed new lights on the original idea of theories of large N. **Please Note: This workshop is not open to the general public, but only to active researchers.**

The AdS/CFT correspondence maps correlators of local operators in a conformal field theory to scattering amplitudes in a gravitational/string theory on curved space-time. The study of such amplitudes is incredibly hard and has mostly been done in a certain classical limit. We show how modern analytic bootstrap techniques allow us to go much beyond that.

LOCATION:Jadwin Hall Room A10 COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200221T130000Z DTEND:20200221T230000Z SUMMARY:PCTS Workshop, "Large N Theories and Strings: Conformal, Confining, and Holographic" DESCRIPTION:**Organizers: Nathan Benjamin, Simone Giombi, Victor Gorbenko, Shota Komatsu, Silviu Pufu, Xinan Zhou**In recent years, there has been much interesting progress from disparate subfields of high energy physics, all under the unifying theme of theories with a large number of degrees of freedom. This includes strings in confining gauge theories, conformal field theories, quantum gravity, and the gauge/string dualities. The purpose of this workshop is to bring together experts in those fields to revisit and shed new lights on the original idea of theories of large N. **Please Note: This workshop is not open to the general public, but only to active researchers.**

**Organizers: Nathan Benjamin, Simone Giombi, Victor Gorbenko, Shota Komatsu, Silviu Pufu, Xinan Zhou**In recent years, there has been much interesting progress from disparate subfields of high energy physics, all under the unifying theme of theories with a large number of degrees of freedom. This includes strings in confining gauge theories, conformal field theories, quantum gravity, and the gauge/string dualities. The purpose of this workshop is to bring together experts in those fields to revisit and shed new lights on the original idea of theories of large N. **Please Note: This workshop is not open to the general public, but only to active researchers.**

I discuss the possibility that the ''dark energy'' that drives the accelerated expansion of the universe arises not from a conventional cosmological constant term in the gravitational action, but rather from a frame-dependent but Weyl scaling invariant action term. This action mimics the standard cosmological action in an unperturbed Friedmann-Robertson-Walker (FRW) cosmology, but has novel consequences both for black hole horizons and, the focus of this talk, for perturbations around the FRW solution. I discuss motivations for a Weyl invariant cosmological action, new insights it would give on old problems, and implications for the recently much discussed ''Hubble Tension''. The talk keeps technicalities to a minimum, requiring only a basic knowledge of FRW cosmology and ordinary differential equations, and concludes with a list of problems for further study, some of which could be undergraduate paper or thesis topics.

LOCATION:Jadwin Hall, Princeton Gravity Initiative, 4th Floor COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200224T193000Z DTEND:20200224T193000Z SUMMARY:High Energy Theory Seminar, "Conformal Fishnet Theory" (Vladimir Kazakov, Ecole Normale Supérieure) DESCRIPTION:I will review the proprieties and recent results for conformal fishnet theory (FCFT) which was proposed by O.Gurdogan and myself as a special double scaling limit of gamma-deformed N=4 SYM theory. FCFT, in its simplest, bi-scalar version, is a UV finite strongly coupled 4-dimensionl logarithmic CFT dominated by planar fishnet Feynman graphs (of the shape of regular square lattice). FCFT inherits the planar integrability of N=4 SYM which becomes manifest in this case: the fishnet graphs can be mapped on the SO(2,4) integrable spin chain (A.Zamolodchikov 1980). The D-dimensional generalization of FCFT, with SO(2,D) conformal symmetry can be also provided. A remarkable property of FCFT is the possibility of spontaneous symmetry breaking, due to the flat vacua which are not lifted by quantum corrections. I will also discuss the exact computation of certain anomalous dimensions and 4-point correlators, and of related fishnet Feynman graphs (of "wheel" or "spiral" type), using the quantum integrability tools: asymptotic and thermodynamic Bethe ansatz and quantum spectral curve of N=4 SYM. LOCATION:Bloomberg Lecture Hall (IAS) COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200225T210000Z DTEND:20200225T210000Z SUMMARY:Pheno & Vino Seminar, "The Higgs Effective Theory is a Black Hole" (Timothy Cohen, University of Oregon) DESCRIPTION:Treating the Standard Model as an Effective Field Theory (EFT) yields a general framework for exploring deviations in observables that probe the indirect effects of new particles. Two treatments are typically discussed --- Higgs EFT (HEFT) and Standard Model EFT (SMEFT) --- my goal in this talk is to compare and contrast them. The key difference between them is that HEFT is formulated assuming electroweak symmetry is broken such that the physical Higgs boson excitation and the Goldstone bosons are treated as independent objects. On the other hand, SMEFT is set in the electroweak symmetric background and utilizes the complete Higgs doublet as a building block. I will argue that in practice when one works with a finite number of EFT operators, HEFT has superior convergence properties for exploring the impact of new particles whose masses are near or below the weak scale. I will then turn to the question of when one is *required* to match onto HEFT, by exploring the singularity structure of the Higgs manifold. Many points will be clarified by relying on a variety of physical examples.

I will describe a formalism for treating Quantum Field Theories in de Sitter space, which, in particular, resolves the issue of infrared divergences often present in perturbation theory.

LOCATION:Bloomberg Lecture Hall (IAS) COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200302T173000Z DTEND:20200302T173000Z SUMMARY:Gravity Initiative Lunch, "The Breakdown of Weak Null Singularities Inside Black Holes" (Maxime Van De Moortel, Princeton University) DESCRIPTION:The characterization of singularities inside black holes is a fundamental problem in General Relativity. While the celebrated “mass inflation” scenario suggests that a weakly *singular* Cauchy horizon forms inside generic black holes (near time-like infinity), the global structure of the black hole interior boundary has largely remained unexplored. I will present my recent proof that, in the context of the spherical collapse of a charged scalar field, the weakly singular Cauchy horizon breaks down in finite retarded time and gives way to either a r = 0 “crushing type” singularity, or a locally naked singularity emanating from the center of symmetry.

LOCATION:Jadwin Hall, Princeton Gravity Initiative, 4th Floor COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200303T210000Z DTEND:20200303T210000Z SUMMARY:Pheno & Vino Seminar, "The 2 to 3 Frontier in NNLO LHC Calculations" (Alexander Mitov, Cavendish Lab, Cambridge) DESCRIPTION:For the last 5 years or so, there has been a major effort towards the calculation of two-loop 5-point QCD amplitudes and their corresponding LHC cross-sections at NNLO. Very recently, the first such calculation - 3-photon production - was completed [arXiv:1911.00479]. I will explain the novel features, and lessons learned, in regard to 5-point two-loop QCD amplitudes. I will also present a detailed comparison of the new NNLO predictions for 3-photon production with existing LHC measurements. Such a comparison is of particular interest given the discrepancy between NLO predictions and data. This calculation represents a stepping stone for tackling another LHC milestone: 3-jet production in NNLO QCD. An update on the ongoing 3-jet calculation will be given. The seminar should be of interest to both theorists and LHC experimentalists.

LOCATION:Jadwin Hall Room 303 COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200306T184500Z DTEND:20200306T184500Z SUMMARY:High Energy Theory Seminar, "Modular Invariance in Superstring Theory from N=4 Super-Yang-Mills" (Silviu Pufu, Princeton University) DESCRIPTION:In this talk, I will first review some of the recent progress on computing holographic correlators using analytic bootstrap techniques combined with supersymmetric localization, focusing on the case of the N = 4 super-Yang-Mills theory. From taking a certain flat space limit of the holographic correlators, one can obtain scattering amplitudes of gravitons in string theory, and one can then reproduce some of the known results for these scattering amplitudes. In particular, from instanton effects in the N=4 SYM theory, I will explain how to reproduce the non-holomorphic Eisenstein series known to appear in type IIB string theory scattering amplitudes.

LOCATION:Princeton University, 407 Jadwin Hall, PCTS Seminar Room COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200309T163000Z DTEND:20200309T163000Z SUMMARY:Gravity Initiative Lunch, "The Quasi-Local Penrose Inequality and the Hoop Conjecture" (Martin Lesourd, Harvard BHI) DESCRIPTION:The Spacetime Inequality of Penrose 1972 says that any slice in any black hole spacetime, the ADM mass of the slice is bounded below by the area of cuts with the event horizon. (Its quasi-local version is a refinement involving quasi-local notions of mass and energy). The Hoop Conjecture proposed by Thorne 1972 says that black holes form when the quasi-local mass M associated with some region of some characteristic length C satisfies ''M > const. C''. These conjectures are open in full generality and I will present some recent progress which proves them in a certain setting. This is joint with S.T. Yau and A. Alaee.

LOCATION:Princeton University, Jadwin Hall, Princeton Gravity Initiative, 4th Floor COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200310T200000Z DTEND:20200310T200000Z SUMMARY:Pheno & Vino Seminar, "Quantum Computing and Machine Learning in High Energy Data Analysis" (Prasnth Shyamsundar, University of Florida) DESCRIPTION:Recently there has been a growing interest in the application of quantum computing and machine learning in many scientific disciplines, including high energy physics. In the first half of this talk, we will look at a novel quantum computing based technique to search for unmodeled deviations from a simulated expectation in high-dimensional collider data. In the second half, we will look at some ways in which the goals of machine learning, as it is used currently in analyses, are not perfectly aligned with the physics goals of the analyses. We will also look at ways of rectifying the demonstrated misalignments.

LOCATION:Jadwin Hall Room 303 COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200316T183000Z DTEND:20200316T183000Z SUMMARY:High Energy Theory Seminar, "Covariant Phase Space with Boundaries" (Daniel Harlow, Massachusetts Institute of Technology) DESCRIPTION:To connect to the HET Seminar via Zoom, please do the following:

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Abstract: The Hamiltonian formulation of mechanics has many advantages, but its standard presentation destroys manifest covariance. This can be avoided by using the "covariant phase formalism" of Iyer and Wald, but until recently this formalism has suffered from several ambiguities related to boundary terms and total derivatives. In this talk I will present a new version of the formalism which incorporates boundary effects from the beginning. This eliminates all ambiguities, and leads to an algorithmic procedure for covariantly constracting the phase space and Hamiltonian of any Lagrangian field theory. It also allows us to confirm that the Poisson bracket in covariant phase space is indeed equivalent to an old proposal of Peierls for computing Poisson brackets covariantly. Along the way I'll illustrate the formalism using various examples. Based on work with Jie-qiang Wu.

LOCATION:https://theias.zoom.us/j/434238729 COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200320T174500Z DTEND:20200320T174500Z SUMMARY:High Energy Theory Seminar, "How to See Everything in the Entanglement Wedge" (Adam Levine, Member, School of Natural Sciences, Institute for Advanced Study) DESCRIPTION:To connect to the HET Seminar via Zoom, please do the following:

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Abstract: We will describe work in progress in which we argue that a generalization of the procedure developed by Gao-Jafferis-Wall can allow one to see the entirety of the entanglement wedge. Gao-Jafferis-Wall demonstrated that one can see excitations behind the horizon by deforming the boundary Hamiltonian using a non-local operator. We will argue in a simple class of examples that deforming the boundary Hamiltonian by a specific modular Hamiltonian can allow one to see (almost) everything in the entanglement wedge. Time permitting, we may comment on connections to previous proposals for bulk reconstruction and possible future directions.

LOCATION:via ZOOM COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200324T200000Z DTEND:20200324T200000Z SUMMARY:Pheno & Vino Seminar, "Direct Detection Experiments in the Gaia Era" (JiJi Fan, Brown University) DESCRIPTION:Please use this link to sign into the remote talk via ZOOM: http://bit.ly/phenoandvino

The advent of the Gaia era has led to potentially revolutionary understanding of dark matter dynamics in our galaxy, which has important consequences for direct detection experiments. In this talk, I will discuss the effects of various dark matter substructures inferred from the Gaia data on possible direct detection signals at next-generation experiments. In particular, I will focus on the implications of the so-called Gaia sausage for the dark matter-nuclear interactions, as well as the unique modulation signatures of several possible streams associated with dark matter-electron interactions.

LOCATION:via ZOOM COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200327T174500Z DTEND:20200327T174500Z SUMMARY:High Energy Theory Seminar, "Solving Random Matrix Models with Positivity" (Henry Lin, Princeton University) DESCRIPTION:To connect to the HET Seminar via Zoom, please do the following:

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Abstract: A new approach to solving random matrix models directly in the large N limit is developed. First, a set of numerical values for some low-pt correlation functions is guessed. The large N loop equations are then used to generate values of higher-pt correlation functions based on this guess. Then one tests whether these higher-pt functions are consistent with positivity requirements, e.g., tr M^{2k} > 0. If not, the guessed values are systematically ruled out. In this way, one can constrain the correlation functions of random matrices to a tiny subregion which contains (and perhaps converges to) the true solution. This approach is tested on single and multi-matrix models and handily reproduces known solutions. It also produces strong results for multi-matrix models which are not believed to be solvable. A tantalizing possibility is that this method could be used to search for new critical points, or string worldsheet theories.

LOCATION:via ZOOM COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200330T163000Z DTEND:20200330T163000Z SUMMARY:Gravity Initiative Lunch - CANCELED, "TBA" (Matthew Heydeman, Princeton University) DESCRIPTION: LOCATION:Jadwin Hall, Princeton Gravity Initiative, 4th Floor COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200330T183000Z DTEND:20200330T183000Z SUMMARY:High Energy Theory Seminar, "Geometry and 5d N=1 QFTs" (Lakshya Bhardwaj, Harvard University) DESCRIPTION:

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**Abstract:** I will explain that a geometric theory built upon the theory of complex surfaces can be used to understand wide variety of phenomena in five-dimensional supersymmetric theories, which includes the following:

- Classification of 5d superconformal field theories (SCFTs).
- Enhanced flavor symmetries of 5d SCFTs.
- 5d N=1 gauge theory descriptions of 5d and 6d SCFTs.
- Dualities between 5d N=1 gauge theories.
- T-dualities between 6d N=(1,0) little string theories.

This relationship between geometry and 5d theories is based on M-theory and F-theory compactifications.

LOCATION:via ZOOM COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200403T174500Z DTEND:20200403T174500Z SUMMARY:Princeton University High Energy Theory Seminar, "The Supersymmetric Cardy Formula from Effective Actions" (Martin Fluder, Princeton University) DESCRIPTION:**To connect to the HET Seminar via Zoom, please do the following:**

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**Abstract:** In this talk I will discuss supersymmetric Cardy formulae in d=4 and d=6. These formulae govern the universal behavior in the high-temperature regime of supersymmetric partition functions — or, in the case of the superconformal index, they govern the high-energy asymptotics of SUSY operators at large energy. I will outline the proof of the Cardy formulae for theories with moduli spaces of vacua, which relies on an effective supersymmetric Chern-Simons action in d-1 dimensions. I will argue that this effective action is universal and intimately related to perturbative as well as global gravitational anomalies. Finally, I will discuss some immediate consequences of our results and briefly compare and distinguish our results to other proposed Cardy formulas.

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**Abstract:** Quantum chaotic dynamics is associated to diverse physical phenomena and signatures. In this talk, we describe progress in building effective theories for three of these: the butterfly effect, the pole skipping phenomenon, and thermalization through the lens of entanglement entropy. We uncover their interplay by showing that the butterfly velocity plays an important role in all three manifestations of chaos. The discussion is informed by results from AdS/CFT and from models of SYK type.

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Via Web Browser / Zoom App: https://unige.zoom.us/j/747717345

Meeting ID: 747 717 345

**Abstract:** The WKB method has played a fundamental role in the development of quantum mechanics. In the 1980s and 1990s, and largely under the influence of Ecalle’s theory of resurgence, it was upgraded to the exact (or complex) WKB method. More recently, developments in supersymmetric gauge theory and string theory have provided a new perspective on this venerable subject. In this talk I will review the basic ingredients of the exact WKB method and present new results inspired by gauge theory/string theory. I will show in particular that the work of Gaiotto-Moore-Neitzke on BPS states provides an elegant solution of the exact WKB method as applied to arbitrary polynomial potentials. I will also discuss some open problems in the subject.

Abstract: In anticipation of the next generation of gravitational wave experiments, I will discuss the opportunities for phenomenological studies of particle physics in the Early Universe. The focus of the talk will be on first order phase transitions and how they can help us address open problems such as the generation of the matter/anti-matter asymmetry, the strong CP-problem, and the nature of the dark sector. I will discuss several such examples and their merit, and comment on complementarity with other experiments.

LOCATION:via ZOOM COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200410T174500Z DTEND:20200410T174500Z SUMMARY:Princeton University High Energy Theory Seminar, "Efficient Rules for All Conformal Blocks: A Dream Come True" (Valentina Prilepina, Laval University) DESCRIPTION:To connect to the HET Seminar via Zoom, please do the following:

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Abstract: In this talk, I will lay out a set of efficient rules for computing d-dimensional global conformal blocks in arbitrary Lorentz representations in the context of the embedding space operator product expansion (OPE) formalism. With these rules in place, the general procedure for determining all possible conformal blocks is reduced to (1) identifying the relevant group theoretic quantities and (2) applying the conformal rules to obtain the blocks. The rules represent a systematic prescription for computing the blocks in a convenient mixed OPE-three-point- function basis as well as a set of rotation matrices, which are necessary to translate these blocks to the pure three-point function basis relevant for the conformal bootstrap. I will start by tracing their origin by describing some of the essential ingredients present in the formalism that naturally give rise to these rules. I will then map out the derivation of the rules, first outlining the general algorithm for the rotation matrices and then proceeding to the conformal blocks. Along the way, l will introduce a convenient diagrammatic notation (somewhat reminiscent of Feynman diagrams), which serves to encode parts of the computation in a compact form. Finally, I will treat several interesting examples to demonstrate the application of these rules in practice.

LOCATION:via ZOOM COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200413T150000Z DTEND:20200413T150000Z SUMMARY:High Energy Theory Seminar, "A New Topological Symmetry of Asymptotically Flat Spacetimes" (Uri Kol, New York University) DESCRIPTION:**To connect to the HET Seminar via Zoom, please do the following:**

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**Abstract:** I will show that the isometry group of asymptotically flat spacetimes contains, in addition to the BMS group, a new dual supertranslation symmetry. The corresponding new conserved charges are akin to the large magnetic U(1) charges in QED. They factorize the Hilbert space of asymptotic states into distinct super-selection sectors and reveal a rich topological structure exhibited by the asymptotic metric. I will describe this structure and some resulting applications, including the construction of a gravitational-magnetic monopole solution analogous to the Wu-Yang monopole and a new gravitational duality akin to electric-magnetic duality.

**Abstract: **Anomalies are powerful constraints on the behavior of quantum field theories. In particular, certain anomalies imply that a QFT is either gapless or spontaneously breaks its global symmetry. We review these ideas and apply them to learn about chiral symmetry breaking in gauge theories.

Abstract: We propose a novel explanation for the smallness of the observed cosmological constant (CC). Regions of space with a large CC are short lived and are dynamically driven to crunch soon after the end of inflation. Conversely, regions with a small CC are metastable and long lived and are the only ones to survive until late times. While the mechanism assumes many domains with different CC values, it does not result in eternal inflation nor does it require a long period of inflation to populate them. We present a concrete dynamical model, based on a super-cooled first order phase transition in a hidden conformal sector, that may successfully implement such a crunching mechanism. We find that the mechanism can only solve the CC problem up to the weak scale, above which new physics, such as supersymmetry, is needed to solve the CC problem all the way to the UV cutoff scale. The absence of experimental evidence for such new physics already implies a mild little hierarchy problem for the CC. Curiously, in this approach the weak scale arises as the geometric mean of the temperature in our universe today and the Planck scale, hinting on a new "CC miracle", motivating new physics at the weak scale independent of electroweak physics. We further predict the presence of new relativistic degrees of freedom in the CFT that should be visible in the next round of CMB experiments. Our mechanism is therefore experimentally falsifiable and predictive.

LOCATION:via ZOOM COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200417T174500Z DTEND:20200417T174500Z SUMMARY:IAS High Energy Theory Seminar, "A Tutorial on Entanglement Island Computations" (Raghu Mahajan, Member, School of Natural Sciences, Institute for Advanced Study) DESCRIPTION:To connect to the HET Seminar via Zoom, please do the following:

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Abstract: In this talk we will present details of quantum extremal surface computations in a simple setup, demonstrating the role of entanglement islands in resolving entropy paradoxes in gravity. The setup involves eternal $AdS_2$ black holes in thermal equilibrium with auxiliary bath systems. We will also describe the extension of this setup to higher dimensions using Randall-Sundrum branes.

LOCATION:via ZOOM COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200420T163000Z DTEND:20200420T163000Z SUMMARY:Gravity Initiative Lunch - CANCELED, "TBA" (Yakov Shlapentokh-Rothman, Princeton University) DESCRIPTION: LOCATION:TBA COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200421T190000Z DTEND:20200421T190000Z SUMMARY:Rutgers NHETC Seminar, "1+1d Adjoint QCD and Non-Invertible Topological Lines" (Kantaro Ohmori, Simons Center for Geometry and Physics) DESCRIPTION:Abstract: In ‘90s, it is claimed that the QCD with massless adjoint quark in 1+1-dimensions is confined, although the fermions cannot screen the Wilson line in the fundamental representation. In this talk, we will see that the confinement can be explained from the topological line operators live in the theory. In particular, non-invertible topological lines, which does not correspond to a symmetry, play a crucial role. This talk is based on a ongoing work with Zohar Komargodski, Sahand Seifnashri, and Konstantinos Roumpedakis.

LOCATION:Remote web conference COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200421T200000Z DTEND:20200421T200000Z SUMMARY:Pheno & Vino Seminar, "New Constraints on Dark Matter from Organic Targets: What Organic Chemistry Can do for Direct Detection" (Carlos Blanco, University of Chicago) DESCRIPTION:Zoom link: bit.ly/phenoandvino

As the age of WIMP-scale dark matter (DM) draws to a close thanks to the ever-increasing sensitivity of direct detection experiments, the majority of sub-GeV DM parameter space remains to be explored. Sub-GeV DM can excite electronic transitions in a variety of molecular and nano-scale systems which have sub-eV scale thresholds. In particular, organic molecules, nanoparticles, and solvated electrons can be used to detect the low momentum recoils of dark matter with electrons and nuclei. Aromatic molecules such as benzene or xylene have an electronic excitation energy of a few eV, making them sensitive to DM as light as a few MeV. These compounds are often used as solvents in organic scintillators, where the de-excitation process leads to a photon which propagates until it is absorbed and re-emitted by a dilute fluor whose emission is not absorbed by the bulk and thus reaches a photomultiplier tube (PMT), Here,we develop the formalism for DM-electron scattering in aromatic organic molecules, calculate the expected sensitivity to DM-electron scattering in benzene and p-xylene, and apply this calculation to EJ-301.

LOCATION:Remote via Zoom
COMMENT:
URL:
END:VEVENT
BEGIN:VEVENT
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DTSTART:20200427T163000Z
DTEND:20200427T163000Z
SUMMARY:Gravity Initiative Lunch - CANCELED, "TBA" (Fani Dosopoulou, Princeton University)
DESCRIPTION:
LOCATION:Jadwin Hall, Princeton Gravity Initiative, 4th Floor
COMMENT:
URL:
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BEGIN:VEVENT
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DTSTART:20200427T173000Z
DTEND:20200427T173000Z
SUMMARY:High Energy Theory Seminar, "Twisted M-theory and Holography" (Davide Gaiotto, Perimeter Institute)
DESCRIPTION:**To connect to the HET Seminar via Zoom, please do the following:**

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**Abstract:** A few years ago, K.Costello proposed how to isolate a self-contained, protected subsector of the M2 brane $AdS_4/CFT_3$ correspondence and demonstrated the holographic duality explicitly for the OPE of the corresponding boundary local operators. The construction can be naturally extended to protected correlation functions, but several new challenges arise. I will discuss how to take the large N limit on the $CFT_3$ side of the story.

In this talk I will revisit and connect various non-perturbative approaches to the quantization of the Seiberg-Witten curves. I will focus on the explicit example of N = 2, SU(2) super Yang–Mills theory, which is closely related to the modified Mathieu operator. I will then show how we can obtain a closed formula for the Fredholm determinant and the spectral traces of this operator.

LOCATION:via web conference - TBA COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200428T200000Z DTEND:20200428T200000Z SUMMARY:Pheno & Vino Seminar, "Statistical Inference of Dark Matter Substructure with Weak and Strong Gravitational Lensing" (Siddharth Mishra-Sharma, New York University) DESCRIPTION:**Zoom link: ** bit.ly/phenoandvino**Abstract:** I will describe two separate methods to statistically infer the properties of dark matter substructure using, in turn, (astrometric) weak and strong lensing observations. In the first part of the talk, I will describe how the motion of dark matter subhalos in the Milky Way induces a correlated pattern of motions in background celestial objects---known as astrometric weak lensing---and how global signatures of these correlations can be measured. These measurement can be used to statistically infer the underlying nature of substructure, and I will show how this can be practically achieved with future astrometric surveys and/or radio telescopes such as WFIRST and the SKA. Next, I will describe a novel method to disentangle the collective imprint of dark matter substructure on extended arcs in galaxy-galaxy strong lensing systems using likelihood-free (or simulation-based) inference techniques. This method uses neural networks to directly estimate the likelihood ratios associated with population-level parameters characterizing substructure within lensing systems. I will show how this method can provide an efficient and principled way to mine the large sample of strong lenses that will be imaged by future surveys like LSST and Euclid to look for signatures of dark matter substructure. I will emphasize how the statistical inference of substructure using these techniques can be used to stress-test the Cold Dark Matter paradigm and probe alternative scenarios such as scalar field dark matter and enhanced primordial fluctuations.

To connect to the HET Seminar via Zoom, please do the following:

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Abstract: When Alice shares thermofield double with Bob, her time evolution can make the wormhole grow. We identify different kinds of operations Alice can do as being responsible for the growth of different parts of spacetime and see how it fits together with subregion duality. With this, we give a quantum circuit interpretation of evaporating black hole geometry. We make an analogy between the appearance of island for evaporating black hole and the transition from two-sided to one-sided black hole in the familiar example of perturbed thermofield double. If Alice perturbs thermofield double and waits for scrambling time, she will have a one-sided black hole with interior of her own. We argue that by similar mechanism the radiation gets access to the interior (island forms) after Page time. The growth of the island happens as a result of the constant transitions from two-sided to one-sided black holes.

LOCATION:via ZOOM COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200504T120000Z DTEND:20200506T210000Z SUMMARY:Joint Princeton Gravity Initiative / PCTS Workshop - CANCELED, "Exploring Supermassive Black Holes" DESCRIPTION:Unfortunately, due to the rapidly escalating health concerns relating to the spread of the coronavirus disease (COVID-19) and in an abundance of caution, we have decided to postpone the workshop until October 14-16, 2020

LOCATION: COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200505T120000Z DTEND:20200505T130000Z SUMMARY:Joint Gravity Initiative / PCTS Workshop - CANCELED, "Exploring Supermassive Black Holes" DESCRIPTION:Unfortunately, due to the rapidly escalating health concerns relating to the spread of the coronavirus disease (COVID-19) and in an abundance of caution, we have decided to postpone the workshop until October 14-16, 2020

Quantum field theory (QFT) works remarkably well for making theoretical predictions in collider scattering experiments. One of the fundamental objects in these calculations, the scattering matrix (S-matrix), is inspired by a well defined operator in non-relativistic quantum mechanics, but is plagued with both ultraviolet (UV) and infrared (IR) divergences in QFT. The UV divergences are now understood through the program of renormalization, but IR divergences remain an active area of research. We have explored three approaches to ameliorate the problem of IR divergences, which will all be discussed in this talk: i) The cross section method, ii) modification of the S-matrix, and iii) the coherent state formalism. The minimal set of processes required for a finite cross section as dictated by the KLN theorem will be elaborated on, along with examining a new approach based on factorization to define finite S-matrix elements in theories with massless particles and its connection to coherent states.

LOCATION:via web conference - TBA COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200506T120000Z DTEND:20200506T120000Z SUMMARY:Joint Princeton Gravity Initiative / PCTS Workshop - CANCELED, "Exploring Supermassive Black Holes" DESCRIPTION:**Abstract:** Over the last few years, the connection between 4d N=2 theories and Hitchin systems has led to a robust exchange of ideas between physics and mathematics. In my talk, I will explain how to extend this dictionary to one between 4d N=2 physics and the SL_N Hitchin system on a nodal UV Curve. I will then use this dictionary to clarify certain questions concerning Coulomb branches of the corresponding Class S theories at various boundaries of the space of marginal parameters. In mathematical terms, I will describe tame SL_N Hitchin systems as a flat family of integrable systems over \bar{M}, the Deligne-Mumford moduli space of the UV Curve. This is based on upcoming work with J. Distler and R. Donagi.

**Zoom link: ** bit.ly/phenoandvino**Abstract:** Cosmic-ray observations provide a powerful probe of dark-matter annihilation in the Galaxy. In this talk I present recent analyses of the AMS-02 antiproton data, reducing cosmic-ray propagation uncertainties by fitting at the same time dark-matter and cosmic-ray propagation parameters. The resulting bounds are among the strongest for heavy dark matter, while for smaller masses, around or below 100 GeV, the analysis exhibits a possible hint for an annihilation signal. Interestingly, the signal is compatible with a thermal annihilation cross section for frozen-out dark matter as well as a dark-matter interpretation of the gamma-ray Galactic center excess. We examine the robustness of this hint by studying the effect of the most important systematic uncertainties: the antiproton production cross sections needed to calculate the source spectra of secondary antiprotons and the potential correlations in the experimental measurements, so far not provided by the AMS-02 Collaboration. While the impact of production cross-section uncertainties is mild, correlation in the AMS-02 data turn out to be decisive and can largely alter the significance of the finding in both directions. The dominant systematics in the rigidity region of interest, around 10-20 GV, arises from uncertainties in the cross sections for cosmic-ray absorption in the AMS-02 detector, the measured flux is corrected for. We compute the corresponding correlations by a careful re-evaluation of the involved absorption cross sections within the Glauber-Gribov model. These correlations diminish the statistical preference for the additional contribution from dark matter. At the same time they enable to further exploit the precision of the AMS-02 data in order to constrain cosmic-ray propagation models.

To connect to the HET Seminar via Zoom, please do the following:

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Abstract: The appearance of BMS symmetry as the asymptotic symmetry of Minkowski spacetime suggests a holographic relation between Einstein gravity and quantum field theory with BMS invariance, dubbed BMSFT. With a three dimensional bulk, the dual BMSFT is a non-Lorentz invariant, two dimensional field theory with infinite-dimensional symmetries. In this talk, I will argue that entanglement entropy in BMSFT can be described by a swing surface in the bulk. For a single interval at null infinity, the corresponding swing surface consists of two ropes which are null geodesics emanating from the entangling surface at the boundary, and a bench, which is a spacelike geodesic extremizing the distance between the ropes.

LOCATION:via ZOOM COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200720T174500Z DTEND:20200720T174500Z SUMMARY:High Energy Theory Seminar, "Non-perturbative Studies of JT Gravity and Supergravity using Minimal Strings" (Clifford V. Johnson, University of Southern California) DESCRIPTION:**To connect to the HET Seminar via Zoom, please click the following link:**

https://theias.zoom.us/j/94395329540?pwd=dUtDMFo4ek9CenRUUVh2UVJSWlk5UT09

Meeting ID: 943 9532 9540**Abstract:** Various Jackiw–Teitelboim (JT) gravity and supergravity theories have been shown (by Saad, Shenker and Stanford, and by Stanford and Witten) to have double scaled random matrix model descriptions, capturing the (spacetime) topological perturbative expansion of the partition function using beautiful recursive methods developed by Mirzakhani and others. I will describe an alternative method for building the matrix model description, using techniques from minimal string theory. This method is particularly useful for supplying non-perturbative definitions of the physics. I apply this to computing - for the first time - the non-perturbative spectral density and spectral form factor for several examples.

**To connect to the HET Seminar via Zoom, please click the following link: **

https://theias.zoom.us/j/98714619023?pwd=YkEzamRpVmNqYXNzbE5DTWtuOGZ3UT09

Meeting ID: 987 1461 9023

Passcode: 338011

** Abstract: **We present a class of Hamiltonians H for which a sector of the Hilbert space invariant under a Lie group G, which is not a symmetry of H, possesses the essential properties of many-body scar states. These include the absence of thermalization and the non-decaying “revivals” of special initial states in time evolution. Some of the scar states found in earlier work may be viewed as special cases of our construction. A particular class of examples concerns interacting spin-1/2 fermions on a lattice consisting of N sites (Fermi-Hubbard model as a special case), and we show that it contains two families of N+1 scar states. One of these families, which was found in recent literature, is comprised of the well-known eta-pairing states that have been linked to superconductivity. We find another family of scar states which is U(N) invariant.

Both families and most of the group-invariant scar states produced by our construction in general, give rise to the off-diagonal long range order which survives at high temperatures and is insensitive to the details of the dynamics. Such states could be used for reliable quantum information processing because the information is stored non-locally, and thus cannot be easily erased by local perturbations. This talk will be based on arXiv:2007.00845.

LOCATION:via ZOOM COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20200810T183000Z DTEND:20200810T183000Z SUMMARY:High Energy Theory Seminar, "Stellar Basins of Gravitationally Bound Particles" (Ken Van Tilburg, KITP, University of California, Santa Barbara) DESCRIPTION:**To connect to the HET Seminar via Zoom, please click the following link:**

https://theias.zoom.us/j/94395329540?pwd=dUtDMFo4ek9CenRUUVh2UVJSWlk5UT09

Meeting ID: 943 9532 9540

Password: 389486**Abstract:** I will describe and explore the consequences of a newly identified physical phenomenon: volumetric stellar emission into gravitationally bound orbits of weakly coupled particles such as axions, moduli, hidden photons, and neutrinos. While only a tiny fraction of the instantaneous luminosity of a star (the vast majority of the emission is into relativistic modes), the continual injection of these particles into a small part of phase space causes them to accumulate over astrophysically long time scales, forming what I call a "stellar basin", in analogy with the geologic kind. The energy density of the Solar basin can surpass that of the relativistic Solar flux at Earth's location after only a million years, for any sufficiently long-lived particle produced through an emission process whose matrix elements are unsuppressed at low momentum. This observation has immediate and striking consequences for direct detection experiments---including new limits on axion and hidden-photon parameter space independent of dark matter assumptions---and may also increase the prospects for indirect detection of weakly interacting particles around stars.

**To connect to the HET Seminar via Zoom, please click the following link:**

https://theias.zoom.us/j/94395329540?pwd=dUtDMFo4ek9CenRUUVh2UVJSWlk5UT09

Meeting ID: 943 9532 9540**Abstract:** I will present enhanced corrections to the entanglement entropy of a subsystem in holographic states. These corrections appear near phase transitions in the entanglement entropy due to competing extremal surfaces, and they are holographic avatars of similar corrections previously found in chaotic energy eigenstates. I will first show explicitly how to find these corrections in chaotic eigenstates by summing over contributions of all bulk saddle point solutions, including those that break the replica symmetry, and by making use of fixed-area states. I will then comment on several intriguing features of this tractable example and discuss a way of understanding these enhanced corrections in other, more general holographic examples.

**To connect to the HET Seminar via Zoom, please click the following link:**

https://princeton.zoom.us/j/93681977694

Meeting ID: 936 8197 7694**Abstract:** I will briefly describe some recent progress in the microscopic understanding of the entropy of certain AdS black holes. I will show how within eleven dimensional supergravity one can compute the logarithmic correction to the Bekenstein-Hawking entropy of certain magnetically charged asymptotically $AdS_4$ black holes with arbitrary horizon topology. The result perfectly agrees with the dual field theory computation of the topologically twisted index for a large class of 3d Chern-Simons matter theories. I will also discuss some progress relevant for rotating, electrically charged $AdS_5$ black holes.

**To connect to the HET Seminar via Zoom, please click the following link:**

https://theias.zoom.us/j/94395329540?pwd=dUtDMFo4ek9CenRUUVh2UVJSWlk5UT09

Meeting ID: 943 9532 9540**Abstract:** Over the last decade it has become clear that there is a close connection between the BPS sector of N=2 supersymmetric field theories in four dimensions and the exact WKB method for analysis of ordinary differential equations (Schrodinger equations and their higher-order analogues). I will review the basic players in this story and some of the main results, and describe some outstanding puzzles.

**To connect to the HET Seminar via Zoom, please click the following link: **

https://theias.zoom.us/j/98714619023?pwd=YkEzamRpVmNqYXNzbE5DTWtuOGZ3UT09

Meeting ID: 987 1461 9023

Passcode: 338011

** Abstract: **I discuss string theory on AdS3xS3xT4 in the tensionless limit, with one unit of NS-NS flux. This theory is conjectured to be dual to the symmetric product orbifold CFT. I show how to compute the full string partition function on various locally AdS3 backgrounds, such as thermal AdS3, the BTZ black and conical defects, and find that it is independent of the actual background, but only depends on the boundary geometry. Consequently, reproducing the boundary partition function does not require a sum over bulk geometries, but rather agrees with the string partition function on any bulk geometry with the appropriate boundary. I argue that the same mechanism shows the factorization of the bulk partition function when geometries with disconnected boundaries are considered.

We propose a new test of strong-field general relativity (GR) based on the universal interferometric signature of the black hole photon ring. The photon ring is a narrow ring-shaped feature, predicted by GR but not yet observed, that appears on images of sources near a black hole. It is caused by extreme bending of light within a few Schwarzschild radii of the event horizon and provides a direct probe of the unstable bound photon orbits of the Kerr geometry. We show that the precise shape of the observable photon ring is remarkably insensitive to the astronomical source profile and can therefore be used as a stringent test of GR. We forecast that a space-based interferometry experiment targeting M87* could test the Kerr nature of the source to the sub-sub-percent level.

LOCATION:via ZOOM COMMENT: URL:https://gravity.princeton.edu/ END:VEVENT BEGIN:VEVENT UID: DTSTART:20200914T183000Z DTEND:20200914T183000Z SUMMARY:High Energy Theory Seminar, "Non-Symmetries, Naturalness, and Two-Dimensional Adjoint QCD" (Zohar Komargodski, Simons Center for Geometry and Physics, Stony Brook University) DESCRIPTION:**To connect to the HET Seminar via Zoom, please click the following link:**

https://theias.zoom.us/j/92467790530?pwd=WUI3U1RCRCtYSjJyV1A2Vmx6dk81QT09

Meeting ID: 924 6779 0530**Abstract:** We will explain the notion of "non-symmetries" or "defect symmetries." We will show that massless two-dimensional QCD admits exponentially many such symmetries. We will use them to prove deconfinement as well as to compute exactly the tension of all $k$-strings in the small mass limit. Finally, we will discuss quartic fermion deformations and exhibit some unexpected phases which we can determine using the defect symmetries.

**To connect to the HET Seminar via Zoom, please click the following link:**

https://theias.zoom.us/j/96660745132?pwd=Y3FPUWVDZlNwUEdINkxjSnNhK0dpZz09

** Abstract: **In conformal field theory, in contrast to gapped theories, S-matrix is not well-defined. Similarly, various inclusive observables which make sense in a gapped theory, such as "energy squared" calorimeters, suffer from IR divergences in CFTs. Using the example of Wilson-Fisher theory, I will discuss how these observables can be renormalized and what is the physical meaning of their anomalous dimensions. Identifying these observables with light-ray operators, I will discuss various related features of the Chew–Frautschi plot in Wilson-Fisher theory, and in particular identify the leading order pomeron operator in this model.

In contrast with the classical stability of stationary, asymptotically flat black holes in four dimensions, some families of higher dimensional black holes suffer from dynamical instabilities. By presenting a mathematical theorem on five-dimensional black rings recently proven in my doctoral thesis, I will argue for the existence of a new instability affecting not only black rings, but a wide class of higher dimensional black holes. This new instability can be directly related to a geometric property of higher dimensional black holes and should be seen as the manifestation of a more general dispersive phenomenon independent of the global, algebraic nature of the spacetime considered.

LOCATION:via ZOOM COMMENT: URL:https://gravity.princeton.edu/ END:VEVENT BEGIN:VEVENT UID: DTSTART:20200921T183000Z DTEND:20200921T183000Z SUMMARY:Princeton University High Energy Theory Seminar, "The Gravitational Path Integral Near Extremality" (Joaquin Turiaci, University of California, Santa Barbara) DESCRIPTION:To join HET Seminar please click link below:

https://princeton.zoom.us/j/98595504817?pwd=QWxDMzFGWjdBdmVBRTFyQmtvajVNQT09(link is external)

Meeting ID: 985 9550 4817

Passcode: 604268

Abstract: I will explain the relation between the Euclidean path integral over near-extremal black hole geometries and its dimensional reduction to 2D Jackiw-Teitelboim gravity. I will focus mostly on the case of 3D gravity and a particular application to pure 3D gravity. I will also mention a connection between more general 2D dilaton-gravity theories, matrix integrals and the minimal string.

To join HET Seminar please click link below:

https://princeton.zoom.us/j/98595504817?pwd=QWxDMzFGWjdBdmVBRTFyQmtvajVNQT09(link is external)

Meeting ID: 985 9550 4817

Passcode: 604268

Abstract: The spectrum of single-trace operators of holographic CFTs at strong coupling and large N can be mapped to the spectrum of Kaluza-Klein modes over the dual AdS supergravity solutions. In this talk, I will focus on two specific CFT3s with AdS4xS7 gravity duals that arise as infrared fixed points of the ABJM M2-brane field theory deformed with a certain quadratic and a certain cubic superpotential. In both cases, the AdS4xS7 product is warped and the metric on S7 is squashed and stretched. In the quadratic case, I will show how Exceptional Field Theory techniques can be used to compute the entire spectrum. In the cubic case, I will show that the spectrum exhibits a space-invaders scenario, similar to that known to occur for another squashed AdS4xS7 solution.

Since the first detection of a gravitational wave event of the merger of two neutron stars in 2017, two more detections in the neutron star mass range have been announced earlier this year. The first one, GW190425, involved an unusually massive neutron star, the second one, GW190814, had a companion in the lower mass gap that could either have been the heaviest neutron star or the lightest black hole ever observed. One of the uncertainties in those detections is allowing for the possibility of having high initial spins before the merger.

In this talk, I will discuss the potential observational impact of the presence of high spins in the inspiral. In particular, I will show what effect high spins can have on the emission of – yet to be observed – electromagnetic precursors and on the mass ejected dynamically during the merger process.

This will be followed by the presentation of a new method to place limits on high spins and small mass ratios in mergers involving a very massive neutron star, such as GW190425.

Finally, I will comment on potential implications for the equation of state, in case the secondary in GW190814 was (once) a neutron star. Following up on the possibility of having low mass black holes in the lower mass gap, I will present the results of an on-going study of near equal mass black hole-neutron star mergers. In particular, I will focus on the impact of initial black hole spin on the viability for electromagnetic counterparts.

LOCATION:via ZOOM COMMENT: URL:https://gravity.princeton.edu/ END:VEVENT BEGIN:VEVENT UID: DTSTART:20200928T183000Z DTEND:20200928T183000Z SUMMARY:High Energy Theory Seminar, "The Holographic Map as a Conditional Expectation" (Thomas Faulkner, University of Illinois Urbana-Champaign) DESCRIPTION:**To connect to the HET Seminar via Zoom, please click the following link:**

https://theias.zoom.us/j/92467790530?pwd=WUI3U1RCRCtYSjJyV1A2Vmx6dk81QT09

Meeting ID: 924 6779 0530**Abstract:** I will demonstrate that holographic error correcting codes naturally give rise to conditional expectations acting on the local operator algebras in the boundary theory. I will use this to give simple derivations of some previously known results as well as some new results when multiple boundary/bulk algebras are considered. Connections to the theory of QFT superselection sectors will be discussed. I will also discuss some shortcomings of these codes as models of AdS/CFT.

We are pleased to announce our Seminar Series on Equity, Diversity and Inclusion, which is **jointly hosted by the Physics and Astrophysics departments**.

This session will provide an introductory overview of the underrepresentation of racial minorities in STEM disciplines specifically the natural sciences. Best practices and strategies to enhance racial diversity and representation will be discussed.

- Overview of racial demographic data across higher education landscape
- Discussion of impacts of underrepresentation on research and teaching mission
- Review of best practices and strategies to enhance racial diversity and representation
- Q/A and open discussion

Shawn Maxam serves as Senior Associate Director for Institutional Diversity and Inclusion in the Office of the Provost. In this role, he leads strategic partnerships and projects associated with campus climate, academic departments, data analysis, and history and sense of place, among others. Shawn joined the Provost Office in 2016 as an Assistant Director. He previously served as the Prevention Coordinator for Men’s Initiatives in Princeton’s University Health Services from 2014 to 2016. Shawn is deeply committed to board service and educational non profits. He serves as a trustee for the Princeton Blairstown Center and the Lawrence Township Education Fund. Shawn earned his BFA from Long Island University and two Masters degrees from Bryn Mawr College in Social Service and Law Social Policy.

LOCATION:Virtual Event via Zoom COMMENT: URL: END:VEVENT BEGIN:VEVENT UID: DTSTART:20201002T174500Z DTEND:20201002T174500Z SUMMARY:High Energy Theory Seminar, "TBA" (Dalimil Mazac, Member, School of Natural Sciences, IAS) DESCRIPTION:**To connect to the HET Seminar via Zoom, please click the following link:**

https://theias.zoom.us/j/96660745132?pwd=Y3FPUWVDZlNwUEdINkxjSnNhK0dpZz09

** Abstract: **TBA

To join HET Seminar please click link below:

https://princeton.zoom.us/j/98595504817?pwd=QWxDMzFGWjdBdmVBRTFyQmtvajVNQT09(link is external)

Meeting ID: 985 9550 4817

Passcode: 604268

Abstract:

To join HET Seminar please click link below:

https://princeton.zoom.us/j/98595504817?pwd=QWxDMzFGWjdBdmVBRTFyQmtvajVNQT09(link is external)

Meeting ID: 985 9550 4817

Passcode: 604268

Abstract:

**To connect to the HET Seminar via Zoom, please click the following link:**

https://theias.zoom.us/j/92467790530?pwd=WUI3U1RCRCtYSjJyV1A2Vmx6dk81QT09

Meeting ID: 924 6779 0530**Abstract:** TBA

Speakers:

- Fabio Antonini, Cardiff University
- Manuela Campanelli, RIT
- Julie Comerford, University of Colorado-Boulder
- Suvi Gezari, University of Maryland
- Steffan Gillessen, MAX PLANCK INSTITUTE (MPE)
- Yuri Levin, Columbia University and Flat Iron Institute, CCA
- Xin Liu, University of Illinois
- Chung-Pei Ma, UC Berkeley
- Brian Metzger, Columbia university
- Diego Munoz, Northwestern University (CIERA)
- Smadar Naoz, UCLA
- Michael Tremmel, Yale
- Karina Voggel, Strasbourg Observatory, France
- Marta Volonteri, Institut d’Astrophysique de Paris (IAP)

**Organizing committee:Fani Dosopoulou, Jeremy Goodman, Jenny Greene, and James Stone**

Speakers:

- Fabio Antonini, Cardiff University
- Manuela Campanelli, RIT
- Julie Comerford, University of Colorado-Boulder
- Suvi Gezari, University of Maryland
- Steffan Gillessen, MAX PLANCK INSTITUTE (MPE)
- Yuri Levin, Columbia University and Flat Iron Institute, CCA
- Xin Liu, University of Illinois
- Chung-Pei Ma, UC Berkeley
- Brian Metzger, Columbia university
- Diego Munoz, Northwestern University (CIERA)
- Smadar Naoz, UCLA
- Michael Tremmel, Yale
- Karina Voggel, Strasbourg Observatory, France
- Marta Volonteri, Institut d’Astrophysique de Paris (IAP)

**Organizing committee:Fani Dosopoulou, Jeremy Goodman, Jenny Greene, and James Stone**

Speakers:

- Fabio Antonini, Cardiff University
- Manuela Campanelli, RIT
- Julie Comerford, University of Colorado-Boulder
- Suvi Gezari, University of Maryland
- Steffan Gillessen, MAX PLANCK INSTITUTE (MPE)
- Yuri Levin, Columbia University and Flat Iron Institute, CCA
- Xin Liu, University of Illinois
- Chung-Pei Ma, UC Berkeley
- Brian Metzger, Columbia university
- Diego Munoz, Northwestern University (CIERA)
- Smadar Naoz, UCLA
- Michael Tremmel, Yale
- Karina Voggel, Strasbourg Observatory, France
- Marta Volonteri, Institut d’Astrophysique de Paris (IAP)

**Organizing committee:Fani Dosopoulou, Jeremy Goodman, Jenny Greene, and James Stone**

**To connect to the HET Seminar via Zoom, please click the following link:**

https://theias.zoom.us/j/96660745132?pwd=Y3FPUWVDZlNwUEdINkxjSnNhK0dpZz09

** Abstract: **TBA

To join HET Seminar please click link below:

https://princeton.zoom.us/j/98595504817?pwd=QWxDMzFGWjdBdmVBRTFyQmtvajVNQT09(link is external)

Meeting ID: 985 9550 4817

Passcode: 604268

Abstract:

To join HET Seminar please click link below:

https://princeton.zoom.us/j/98595504817?pwd=QWxDMzFGWjdBdmVBRTFyQmtvajVNQT09(link is external)

Meeting ID: 985 9550 4817

Passcode: 604268

Abstract:

**To connect to the HET Seminar via Zoom, please click the following link:**

https://theias.zoom.us/j/92467790530?pwd=WUI3U1RCRCtYSjJyV1A2Vmx6dk81QT09

Meeting ID: 924 6779 0530**Abstract:** We show that a naïve application of the quantum extremal surface (QES) prescription can lead to paradoxical results and must be corrected at leading order. The corrections arise when there is a second QES (with strictly larger generalized entropy at leading order than the minimal QES), together with a large amount of highly incompressible bulk entropy between the two surfaces. We trace the source of the corrections to a failure of the assumptions used in the replica trick derivation of the QES prescription, and show that a more careful derivation correctly computes the corrections. Using tools from one-shot quantum Shannon theory (smooth min-and max-entropies), we generalize these results to a set of refined conditions that determine whether the QES prescription holds. We find similar refinements to the conditions needed for entanglement wedge reconstruction (EWR), and show how EWR can be reinterpreted as the task of one-shot quantum state merging (using zero-bits rather than classical bits), a task gravity is able to achieve optimally efficiently.

**To connect to the HET Seminar via Zoom, please click the following link:**

https://theias.zoom.us/j/96660745132?pwd=Y3FPUWVDZlNwUEdINkxjSnNhK0dpZz09

** Abstract: **TBA

To join HET Seminar please click link below:

https://princeton.zoom.us/j/98595504817?pwd=QWxDMzFGWjdBdmVBRTFyQmtvajVNQT09(link is external)

Meeting ID: 985 9550 4817

Passcode: 604268

Abstract:

To join HET Seminar please click link below:

https://princeton.zoom.us/j/98595504817?pwd=QWxDMzFGWjdBdmVBRTFyQmtvajVNQT09(link is external)

Meeting ID: 985 9550 4817

Passcode: 604268

Abstract:

**To connect to the HET Seminar via Zoom, please click the following link:**

https://theias.zoom.us/j/96660745132?pwd=Y3FPUWVDZlNwUEdINkxjSnNhK0dpZz09

** Abstract: **TBA

To join HET Seminar please click link below:

https://princeton.zoom.us/j/98595504817?pwd=QWxDMzFGWjdBdmVBRTFyQmtvajVNQT09(link is external)

Meeting ID: 985 9550 4817

Passcode: 604268

Abstract:

**To connect to the HET Seminar via Zoom, please click the following link:**

https://theias.zoom.us/j/96660745132?pwd=Y3FPUWVDZlNwUEdINkxjSnNhK0dpZz09

** Abstract: **TBA