Counting States of Near-Extremal Black Holes

TL;DR

This paper demonstrates that the entropy of a near-extremal black string matches the count of string states, enabling analysis of Hawking decay via string perturbation theory and confirming its unitarity.

Contribution

It establishes a precise correspondence between black string entropy and string state counts near extremality, facilitating perturbative analysis of Hawking decay.

Findings

Black string entropy matches string state count

Hawking decay can be analyzed perturbatively

Decay process shown to be perturbatively unitary

Abstract

A six-dimensional black string is considered and its Bekenstein-Hawking entropy computed. It is shown that to leading order above extremality, this entropy precisely counts the number of string states with the given energy and charges. This identification implies that Hawking decay of the near-extremal black string can be analyzed in string perturbation theory and is perturbatively unitary.