Conditions for superradiant instability of the Kerr-Newman black holes

TL;DR

This paper establishes the conditions under which Kerr-Newman black holes become superradiantly unstable or stable when perturbed by a charged massive scalar field, based on potential analysis.

Contribution

It introduces specific criteria for superradiant instability and stability of Kerr-Newman black holes, extending previous understanding to charged scalar perturbations.

Findings

Identified conditions for superradiant instability involving trapping wells.

Derived criteria for superradiant stability with no trapping well.

Applied analysis to Kerr black holes to determine instability conditions.

Abstract

We find two conditions for superradiant instability of Kerr-Newman black holes under a charged massive scalar perturbation by analyzing asymptotic scalar potential and far-region wave function. Actually, they correspond to the condition for getting a trapping well. Also, we obtain the conditions for superradiant stability of Kerr-Newman black holes which states that there is no trapping well. The analysis is applied to Kerr black holes to find a condition for superradiant instability.