Spring 2023 Physics Seminar

The Physics Seminar will take place Wednesdays at 2:00pm in SCGP 313

Feb 1   Hong Liu  
Feb 8 IR N-alities with Abelian Hypermultiplets Anindya Dey

I will discuss a recently proposed class of IR dualities in three space-time dimensions with eight supercharges.

Feb 15  
Brian Williams
Feb 22

The string/black hole transition in anti de Sitter Space

Erez Urbach  
March 8   Aleix Gimenez-Grau  
March 15 When Light Strings Don’t Look Like Particles Sunny Itzhaki
In certain time-dependent backgrounds there are nonstandard light strings that are created classically in an instant and cannot be approximated by particles. We discuss the implications of these strings to black holes and cosmology.
March 21 at 2:30pm An overview of CFT in momentum space Kostas Skenderis 
I will give an overview of conformal field theory in momentum space. I will present the solution of the conformal Ward identities in momentum space and discuss renormalisation and anomalies.
March 22 Supersymmetric wormholes in gravity and SYK Henry Lin

I will discuss some geometric properties of Einstein-Rosen wormholes joining two extremal black holes. These properties yield predictions for the zero temperature physics of certain supersymmetric quantum mechanical models. For example, the probability that the wormhole is very short is related to the fraction of states in the dual quantum mechanics that are ground states. I will report detailed checks of these properties using the \cal N = 2 SYK model.

March 29   Daniel Ranard  
April 5 Hydrodynamics and Corrections to Random Matrix Universality in Quantum Chaos Brian Swingle
Ensembles of quantum chaotic systems typically exhibit random-matrix-like correlations in the statistics of their energy levels, and the spectral form factor is a useful way to diagnose these correlations. However, real physical systems have non-random structure, like locality and associated slow modes, which should affect these spectral correlations. I will present a theory that predicts the time-dependence of the spectral form factor based on an effective field theory of the relevant slow modes. I will discuss applications of this theory to a variety of systems, including to models with glassy dynamics and sound poles, and I will also relate these early-time corrections to a corresponding effect at late time. Based on work with Mike Winer and with Richard Barney, Chris Baldwin, and Victor Galitski.
April 12 On Causality Conditions in de Sitter Spacetime Rachel Rosen

Causality conditions provide powerful constraints on low energy theories. In this talk, I will discuss how standard causality conditions of AdS and flat spacetimes can be extended to de Sitter spacetime. In particular, I will consider the Shapiro time delay experienced by a particle in a black hole or shockwave background and discuss how “fastest null geodesics” can be defined using spatial shifts on the boundary of de Sitter and the relevance of the “stretching” of the de Sitter Penrose diagram. I will discuss the case of a photon with a non-canonical coupling as an illustrative example.

April 19 Bulk-local diagrams for higher-spin gravity, using its “BPS black hole Yasha Neiman I make a surprising connection between two long-standing problems in higher-spin gravity: (1) locality concerns at the quartic order in perturbation theory, and (2) the physical meaning of the Didenko-Vasiliev “BPS black hole” solution. I show that the Didenko-Vasiliev solution is dual to a bilocal single-trace operator in the holographically dual vector model, just like the string in standard AdS/CFT is dual to a Wilson line. This suggests that we should use these solutions as a “completion” of the space of on-shell higher-spin fields, much like the string “completes” its associated tower of particle species. All n-point boundary correlators can then be constructed from (sufficiently local) cubic vertices, via a new string-like diagrammatic framework. Thus, the quartic locality problem is avoided, at the price of introducing a new bulk object. In the process, an infinite tower of unknown vertices in the standard formulation is replaced by a single unknown cubic vertex.
April 26   Francesco Galvagno  

*May 2 at 1pm

Parisi’s hypercube, Fock-space fluxes and NAdS$_2$/NCFT$_1$ holography Yiyang Jia  We consider a model of Parisi where a single particle hops on an infinite-dimensional hypercube, under the influence of a uniform but disordered magnetic flux. We reinterpret the hypercube as the Fock-space graph of a many-body Hamiltonian, and the flux as a frustration of the return amplitudes in Fock space. We will show that this model has the same correlation functions as the double-scaled Sachdev-Ye-Kitaev model, and hence is an equally good quantum model for near-AdS$_2$/near-CFT$_{1}$ holography. Unlike the SYK model, the hypercube Hamiltonian is not $p$-local. Instead, the SYK model can be understood as a Fock-space model with similar frustrations. Hence we propose this type of Fock-space frustration as the broader characterization for NAdS$_2$/NCFT$_1$ microscopics, and speculate the possible origin of such frustrations.
May 3 Pushing the Precision Frontier of Real-World Gravity via Modern QFT Michele Levi We will review the tower of EFTs for the radiating binary inspiral, including our unique bootstrapping of the EFT of a spinning particle in gravity. We will then present our recent progress in this bootstrapping, and our unique push of the real-world precision frontier in 3 fronts: High loop, and higher spin — in the conservative sector, and also going
into the radiative sector — if time permits.
May 10 Reconstructing Gauge Group from Extended Operators Rajath Krishna Radhakrishnan

The structure of the gauge group constrains the properties of operators in a gauge theory. In this talk, I will consider the reverse direction and ask what properties of a (finite) gauge group can be reconstructed from the operators in a gauge theory. I will first consider OPE/fusion rules of Wilson lines, and explain various properties of the gauge group that can be deduced from it. Then I will introduce certain surface operators which exist in any gauge theory. I will describe the fusion rules of these surface operators, and show that, in general, there are properties of the gauge group that can be reconstructed from the fusion rules of surface operators which cannot be obtained from the fusion rules of Wilson lines, and vice-versa. This talk is based on arXiv:2302.08419.

May 16 5d to 3d compactifications and discrete-anomaly matching Orr Sela  
May 17   Murat Kologlu  
May 24  
Yi-Zhouang You
May 30   Stefano Baiguera  
May 31 Non-Perturbative Defects in Tensor Models from Melonic Trees Fedor Popov