Worldsheet computation of heavy-light correlators

TL;DR

This paper calculates string worldsheet correlators for heavy black hole microstates and finds exact agreement with dual CFT predictions, including for amplitudes related to Hawking radiation, demonstrating the consistency of the holographic duality.

Contribution

It constructs and computes novel heavy-light correlators in solvable null-gauged WZW models and confirms their agreement with the dual symmetric orbifold CFT, including complex amplitudes.

Findings

Exact agreement between worldsheet and CFT correlators for heavy-light interactions.

Derived a general formula for n-light insertion correlators on these backgrounds.

Confirmed the matching of a heavy-light five-point function from both approaches.

Abstract

We compute a large collection of string worldsheet correlators describing light probes interacting with heavy black hole microstates. The heavy states consist of NS5 branes carrying momentum and/or fundamental string charge. In the fivebrane decoupling limit, worldsheet string theory on a family of such backgrounds is given by exactly solvable null-gauged WZW models. We construct physical vertex operators in these cosets, including all massless fluctuations. We first compute a large class of novel heavy-light-light-heavy correlators in the AdS$_3$ limit, where the light operators include those dual to chiral primaries of the holographically dual CFT. We compare a subset of these correlators to the holographic CFT at the symmetric product orbifold point, and find precise agreement in all cases, including for light operators in twisted sectors of the orbifold CFT. The agreement is highly non-trivial, and includes amplitudes that describe the analogue of Hawking radiation for these microstates. We further derive a formula for worldsheet correlators consisting of $n$ light insertions on these backgrounds, and discuss which subset of these correlators are likely to be protected. As a test, we compute a heavy-light five-point function, obtaining precisely the same result both from the worldsheet and the symmetric orbifold CFT. This paper is a companion to and extension of [arXiv:2203.13828].