AdS black holes as reflecting cavities

TL;DR

This paper investigates the analytic structure of thermal Green functions in AdS black holes, revealing a reflecting cavity picture where null rays bounce on boundaries, and derives asymptotic quasinormal mode frequencies.

Contribution

It introduces a novel interpretation of AdS black holes as reflecting cavities and provides a general formula for quasinormal mode frequencies in large AdS black holes.

Findings

Null singularities correspond to boundary time singularities.

Null rays bounce on boundaries, forming a reflecting cavity.

Derived asymptotic quasinormal mode frequencies.

Abstract

We use the identification between null singularities of correlators in the bulk with time singularities in the boundary correlators to study the analytic structure of time-dependent thermal Green functions using the eikonal approximation for classical solutions in the AdS black hole background. We show that the location of singularities in complex time can be understood in terms of null rays bouncing on the boundaries and singularities of the eternal black hole, giving the picture of a `reflecting cavity'. We can then extract the general analytic expression for the asymptotic values of the frequencies of quasinormal modes in large AdS black holes.