Speaker: Lefteris Papantonopoulos (National Technical University of Athens)
After reviewing the basic ideas on superradiance, we discuss the dynamics of a massive charged scalar wave coupled kinematically to curvature, scattered off the horizon of a Reissner-Nordstr\"om black hole. Then, we present an exact solution of a four-dimensional AdS charged hairy black hole and discuss its stability in the near extremal and extremal limits. By employing
the improved asymptotic iteration method and the time domain analysis we find the quasinormal frequencies. For the charged scalar perturbations, we find the superradiance condition by computing the reflection coefficient in the low-frequency limit and we show that in the superradiance regime, which depends on the scalar hair charge, all modes of radial charged massless perturbations are unstable, indicating that the charged hairy black hole is superradiantly unstable. On the other hand, calculating the quasinormal frequencies of radial neutral scalar perturbations in this background, we found stability of the charged hairy black hole.