Dyonic Black Holes in String Theory

TL;DR

This paper presents an exact static, spherically symmetric dyonic black hole solution in string theory, exploring its properties such as temperature and entropy, and comparing it with prior solutions.

Contribution

The paper provides a new exact dyonic black hole solution in string theory, analyzing its properties and relations to previous solutions by Gibbons, Maeda, and others.

Findings

Hawking temperature depends on electric and magnetic charges.

Extremal dyonic black holes have zero temperature and nonzero entropy.

The solution is related to previously known solutions via coordinate transformations.

Abstract

An exact solution of the low-energy string theory representing static, spherical symmetric dyonic black hole is found. The solution is labeled by their mass, electric charge, magnetic charge and asymptotic value of the scalar dilaton. Some interesting properties of the dyonic black holes are studied. In particular, the Hawking temperature of dyonic black holes depends on both the electric and magnetic charges, and the extremal ones, which have nonzero electric and magnetic charges, have zero temperature but nonzero entropy. These properties are quite different from those of electrically (or magnetically) charged dilaton black holes found by Gibbons {\it et al.} and Garfinkle {\it et al.}, but are the same as those of the dyonic black holes found by Gibbons and Maeda. After this paper was submitted for publication, D. Wiltshire told us that solutions, eqs.(22)-(28), are related to Gibbons-Maeda dyonic black hole solutions by a coordinate transformation and some parameters reparametization \cite{26}. And, we were also informed that many of our results were previously obtained by Kallosh {\it et al.} \cite{27}. The dyonic black hole solutions, eqs.(22)-(28), are also related to those of reference \cite{27} by another coordinate