Superradiant instability of dyonic black holes in string theory

TL;DR

This paper investigates the superradiant stability of dyonic black holes in string theory, revealing their increased instability compared to Reissner-Nordström black holes due to magnetic charge coupling, and identifies stable parameter regions.

Contribution

It provides the first analysis of superradiant stability for dyonic black holes in string theory, highlighting the effects of magnetic charge coupling on instability.

Findings

Dyonic black holes are more unstable than RN black holes due to magnetic charge coupling.

Two stable regions in parameter space for superradiant stability are identified.

Coupling between magnetic charge and scalar waves influences superradiant behavior.

Abstract

When a scalar wave perturbation is properly scattering off a charged or rotating black hole, the energy of the reflected scalar wave may be amplified. This is a superradiant process. If this amplification process can occur back and forth through certain confining mechanism, it will lead to strong instability of the black hole. In this paper, the superradiant stability is investigated for a special kind of dyonic black holes in string theory. Although the dynoic black hole has a similar spacetime metric with a electrically charged RN black hole, it is found that the dyonic black hole is more unstable than a RN black hole due to the coupling between magnetic charge of the dyonic black hole and the imping electrically charged scalar wave. We find two superradiantly stable regions in the parameter space for the dyonic black holes and charged massive scalar perturbation.