Superradiance of charged black holes in Einstein-Gauss-Bonnet Gravity

TL;DR

This paper demonstrates that charged black holes in Einstein-Gauss-Bonnet gravity exhibit superradiant instability influenced by higher curvature corrections, marking the first such study with these terms present.

Contribution

It provides the first analysis of superradiant instability in Einstein-Gauss-Bonnet gravity, showing how higher curvature terms affect the critical mirror radius.

Findings

Superradiant instability occurs for charged black holes with a mirror outside the horizon.

The critical radius for instability decreases as the Gauss-Bonnet coupling increases.

This is the first example of superradiance with higher curvature corrections in the action.

Abstract

In this paper we show that electrically charged black holes in Einstein-Gauss-Bonnet gravity suffer from a superradiant instability. It is triggered by a charged scalar field that fulfills Dirichlet boundary conditions at a mirror located outside the horizon. As in General Relativity, the unstable modes exist provided the mirror is located beyond a critical radius, making the instability a long wavelength one. We explore the effects of the Gauss-Bonnet corrections on the critical radius and find evidence that the critical radius decreases as the Gauss-Bonnet coupling $\alpha$ increases. Due to the, up to date, lack of an analytic rotating solution for Einstein-Gauss-Bonnet theory, this is the first example of a superradiant instability in the presence of higher curvature terms in the action.