David McGady - "Black hole evaporation and semiclassicality at large D" and De-liang Zhong - "Thermodynamic Bethe Ansatz for Fishnet CFT"

by David McGady (Nordita), De-liang Zhong (Tel Aviv University)

Monday 16 Dec 2019, 12:00 → 13:00 Europe/Zurich

4/2-037 - TH meeting room (CERN)

Speaker: David McGady
Title: Black hole evaporation and semiclassicality at large D
Abstract: Black holes are very fast information scramblers. In this talk, we study Schwarzschild black holes in D-dimensions. While information scrambling times depend weakly on D, black hole evaporation times decay roughly as D^D. We find D-dimensional black holes whose curvature scales at the horizon are parametrically much longer than the Planck length even though their evaporation times are, formally, much shorter than their scrambling times (or indeed any other fixed timescale). Of course, this cannot happen. Indeed, for black hole physics to be semiclassical to begin with, the black hole must have scrambled the information of the states behind its horizon: at large-D requiring fast scrambling places the strongest limits on semiclassicality. We comment on "realistic" models of quantum gravity in D \leq 26.

Speaker: De-liang Zhong
Title: Thermodynamic Bethe Ansatz for Fishnet CFT
Abstract: We present the TBA equations and the Y-system for the exact spectrum of general multi-magnon local operators in the D-dimensional anisotropic version of the bi-scalar fishnet CFT. The mixing matrix of such operators is given in terms of fishnet planar graphs of multi-wheel and multi-spiral type. These graphs probe the two main building blocks of the TBA approach that are the magnon dispersion relation and the magnon scattering matrix and which we both obtain by diagonalising suitable graph-building operators. We also obtain the dual version of the TBA equations, which relates, in the continuum limit, D-dimensional graphs to two-dimensional sigma models in AdS D+1. It allows us to verify a general formula obtained by A. Zamolodchikov for the critical coupling.