IAS High Energy Theory Seminar

Light-rays and detectors in Wilson-Fisher theory

Petr Kravchuk
Member, School of Natural Sciences, IAS
September 18, 2020
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.

Partition functions of the tensionless string

Lorenz Eberhardt
Member, School of Natural Sciences, Institute for Advanced Study
August 28, 2020
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.

An update on exact WKB and supersymmetric field theory

Andy Neitzke
Yale University
August 24, 2020
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.

Enhanced Corrections to the Page Curve near Holographic Entanglement Transitions

Xi Dong
University of California, Santa Barbara
August 17, 2020
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.

Many Body Scars as a Group Invariant Sector of Hilbert Space

Kiryl Pakrouski
Princeton University
July 24, 2020
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.

Non-perturbative Studies of JT Gravity and Supergravity using Minimal Strings

Clifford V. Johnson
University of Southern California
July 20, 2020
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.

Entanglement Entropy in Flat Holography

Wei Song
Member, School of Natural Sciences, Institute for Advanced Study; Tsinghua University
May 15, 2020
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.

A Quantum Circuit Interpretation of Evaporating Black Hole Geometry

Ying Zhao
Member, School of Natural Sciences, Institute for Advanced Study
May 1, 2020
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.

Twisted M-theory and Holography

Davide Gaiotto
Perimeter Institute
April 27, 2020
A few years ago, K.Costello proposed how to isolate a self-contained, protected subsector of the M2 brane AdS4/CFT3 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 CFT3 side of the story.