Superradiant Scattering of Charged Scalar Fields in Cosmological Black Hole Spacetimes

Black holes offer a unique opportunity to investigate fields connected to unknown physics, such as dark matter. One such process, superradiant scattering, involves a field extracting energy from a black hole. This work studies the amplification of charged scalar fields in Kiselev spacetimes, which generalize the Reissner-Nordström-de Sitter metric and describe non-rotating black holes in a universe with a cosmological constant, accounting for dark energy-like environments. We compute superradiant scattering, the characteristic oscillations of the black hole (quasi-normal modes), and the spectra of quasi-bound states, where the field is temporarily trapped around the black hole.