Universality of the quasinormal spectrum of near-extremal Kerr–Newman black holes

Abstract

Our current knowledge about the quasinormal resonance spectrum of charged and rotating Kerr–Newman black holes is quite poor. This unsatisfactory situation is a direct consequence of the fact that all attempts to decouple the gravitational and electromagnetic perturbations of generic Kerr–Newman black holes have failed thus far. Recently, Zilhao et al. (Phys Rev D 90:12, 124088, 2014. arXiv:1410.0694) have studied the nonlinear stability of Kerr–Newman black holes. We show here that their numerical results for the time evolutions of the spacetime deformations of near-extremal Kerr–Newman black holes are described extremely well by a simple and universal analytical formula for the quasinormal resonances of the black holes. This formula is expressed in terms of the black-hole physical parameters: the horizon angular velocity \(\Omega _{\text {H}}\) and the Bekenstein–Hawking temperature \(T_{\text {BH}}\).