Analytic study of superradiant stability of Kerr–Newman black holes under charged massive scalar perturbation

The superradiant stability of a Kerr–Newman black hole and charged massive scalar perturbation is investigated. We treat the black hole as a background geometry and study the equation of motion of the scalar perturbation. From the radial equation of motion, we derive the effective potential experienced by the scalar perturbation. By a careful analysis of this effective potential, it is found that when the inner and outer horizons of Kerr–Newman black hole satisfy r - r + ⩽ 1 3 and the charge-to-mass ratios of scalar perturbation and black hole satisfy q μ Q M > 1 , the Kerr–Newman black hole and scalar perturbation system is superradiantly stable.