Condition for superradiance in higher-dimensional rotating black holes

Abstract

It is shown that the superradiance modes always exist in the radiation by the (4+n)-dimensional rotating black holes. Using a Bekenstein argument the condition for the superradiance modes is shown to be 0<ω<mΩ for the scalar, electromagnetic and gravitational waves when the spacetime background has a single angular momentum parameter about an axis on the brane, where Ω is a rotational frequency of the black hole and m is an azimuthal quantum number of the radiated wave.