Abstract: I will describe a class of non-perturbative corrections to the density matrix of Hawking radiation, and discuss the connection to the information paradox. The effect comes from “replica wormholes”, connecting different copies in the replica trick, which leave an imprint on the physical density matrix. In two-dimensional JT gravity coupled to large-N matter fields, this is calculated in several … Read More

abstract: I will discuss a few aspects of Jackiw-Teitelboim gravity with positive cosmological constant. It may be understood as a toy model for de Sitter quantum gravity, in which one may reliably compute transition amplitudes for the creation or annihilation of a baby universe, sum up gravitational loops, and study the fate of unitarity.

Abstract: 3d N=4 gauge theories admit two distinct topological twists, ‘A’ and ‘B’, analogous to the well-studied A and B twists of 2d N=(2,2) theories, and exchanged by 3d mirror symmetry. Unlike their 2d analogues, much of the categorical structure of the 3d twists is still being worked out. I will discuss some aspects of the category of line operators … Read More

The leading part of the M-theory low-energy effective action has been conjectured to be the minimal supersymmetric completion of curvature-to-the-fourth corrections to the eleven-dimensional supergravity action. This fact is difficult to exploit, because a component Noether procedure would have an infinite number of steps of ever-higher order in the curvature expansion, and any 11D, N=1 superspace will put the theory … Read More

Hawking famously discovered a tension between semiclassical gravity and the unitary evolution of quantum mechanics when black holes evaporate. I’ll describe a semiclassical calculation that nonetheless reproduces signatures of unitarity, namely the “Page curve” of entropy evolution and the Hayden-Preskill protocol. The new input, coming from recent advances in AdS/CFT, involves a “quantum extremal surface”, a stationary surface for Bekenstein’s … Read More

Abstract: “I will give an overview and some of the highlights of a research program initiated in 2013 with Gadde and Putrov, the main subject of which is the study of 2d-3d combined systems that involve 3d N=2 theories with 2d N=(0,2) boundary conditions. We will see how holomorphic-topological twists of such systems lead to boundary chiral algebras, somewhat similar … Read More

Abstract: Two dimensional conformal field theories are among the most important quantum field theories: they describe important statistical and condensed matter systems near criticality, and — while not exactly solvable — many exact techniques can be used which are not available in higher dimensions. For example, Cardy used modular invariance to derive a universal asymptotic formula for the high energy … Read More

Summary: For an old evaporating black hole the entanglement wedge of radiation can include an entanglement island that covers a big portion of the black hole interior. We explore a few simple cases where these islands appear and lead to a resolution of apparent information problems. We also discuss how these islands arise through a standard replica trick computation of … Read More