The black hole behind the cut

TL;DR

This paper analyzes the analytic structure of holographic correlators in AdS3/CFT2, revealing how black hole microstates influence correlator singularities and connect to quasi-normal modes.

Contribution

It provides an explicit computation of heavy-heavy-light-light correlators involving black hole microstates using Heun equations and Liouville CFT techniques.

Findings

Correlator poles become dense and form a cut in the black hole regime.

Discontinuities across the cut correspond to BTZ quasi-normal modes.

Behavior mimics large central charge black hole microstate expectations.

Abstract

We study the analytic structure of the heavy-heavy-light-light holographic correlators in the supergravity approximation of the AdS$_3 \times S^3$/CFT$_2$ duality. As an explicit example, we derive the correlator where the heavy operator is a classical microstate of the 5D supersymmetric black hole and its dual geometry interpolates as a function of a continuous parameter between global AdS$_3$ and the extremal BTZ black hole. The simplest perturbation of this interpolating geometry by a light field is described by the Heun equation and we exploit the relation of its connection coefficients to the Liouville CFT to analytically compute the correlator in the two limits, focusing in particular on the black hole regime. In this limit we find that the real poles of the correlator become dense and can be approximated by a cut. We show that, when the charges of the heavy state are in the black hole regime, the discontinuity across the cut has complex poles corresponding to the quasi-normal modes of BTZ. This behaviour is qualitatively similar to what is expected for the large central charge limit of a typical black hole microstate