Strings in a 2-d Extremal Black Hole

TL;DR

This paper explores string theory in 2D extremal black hole backgrounds, revealing symmetry enhancements, entropy consistency with semi-classical results, and potential dualities with N=(2,1) strings.

Contribution

It provides a detailed analysis of string dynamics in 2D extremal black holes, demonstrating symmetry enhancement and proposing a duality with N=(2,1) strings.

Findings

Symmetry enhancement to Virasoro in 2D black hole backgrounds

Entropy matches semi-classical calculations

Evidence of flux absorption by the black hole

Abstract

String theory on 2-d charged black holes corresponding to (SL(2)xU(1)_L)/U(1) exact asymmetric quotient CFTs are investigated. These backgrounds can be embedded, in particular, in a two dimensional heterotic string. In the extremal case, the quotient CFT description captures the near horizon physics, and is equivalent to strings in AdS_2 with a gauge field. Such string vacua possess an infinite space-time Virasoro symmetry, and hence enhancement of global space-time Lie symmetries to affine symmetries, in agreement with the conjectured AdS_2/CFT_1 correspondence. We argue that the entropy of these 2-d black holes in string theory is compatible with semi-classical results, and show that in perturbative computations part of an incoming flux is absorbed by the black hole. Moreover, on the way we find evidence that the 2-d heterotic string is closely related to the N=(2,1) string, and conjecture that they are dual.