Strings as Solitons & Black Holes as Strings

TL;DR

This paper constructs exact supergravity solutions representing string states and supersymmetric black holes, supporting the idea that black hole entropy can be explained by string state counting.

Contribution

It presents a class of exact solutions linking string states to black holes, demonstrating their degeneracy and implications for string duality and black hole entropy.

Findings

Exact solutions correspond to string states in supergravity.

Black hole entropy relates to string state degeneracy.

Solutions include rotating, charged black holes with string sources.

Abstract

Supersymmetric closed string theories contain an infinite tower of BPS-saturated, oscillating, macroscopic strings in the perturbative spectrum. When these theories have dual formulations, this tower of states must exist nonperturbatively as solitons in the dual theories. We present a general class of exact solutions of low-energy supergravity that corresponds to all these states. After dimensional reduction they can be interpreted as supersymmetric black holes with a degeneracy related to the degeneracy of the string states. {}For example, in four dimensions we obtain a point-like solution which is asymptotic to a stationary, rotating, electrically-charged black hole with Regge-bounded angular momentum and with the usual ring-singularity replaced by a string source. This further supports the idea that the entropy of supersymmetric black holes can be understood in terms of counting of string states. We also discuss some applications of these solutions to string duality.