The string spectrum on the horizon of a non-extremal black hole

TL;DR

This paper analyzes the spectrum of strings near a five-dimensional non-extremal black hole horizon, revealing an exactly solvable conformal field theory and identifying states that match the black hole's mass, with implications for understanding black hole entropy.

Contribution

It provides the exact modular invariant spectrum of string states in a non-extremal black hole background, connecting string excitations to black hole properties.

Findings

States with only right-moving excitations match the black hole's ADM mass.

The horizon theory reduces to an exactly solvable conformal field theory.

Discussion on the statistical entropy of black holes included.

Abstract

We investigate the conformal string $\sigma $-model corresponding to a general five-dimensional non-extremal black hole solution. In the horizon region the theory reduces to an exactly solvable conformal field theory. We determine the modular invariant spectrum of physical string states, which expresses the Rindler momentum operator in terms of three charges and string oscillators. For black holes with winding and Kaluza-Klein charges, we find that states made with only right-moving excitations have ADM mass equal to the black hole ADM mass, and thus they can be used as sources of the gravitational field. A discussion on statistical entropy is included.