Scalar clouds around spinning black holes

Abstract

One of the promising dark matter candidates is the ultra-light boson. A piece of observation evidence may come from black holes and their surroundings. Indeed, clouds made of ultra-light scalar particles should grow via the superradiance process and bind to spinning black holes. It turns out that the energy spectrum and the occupation of this cloud are similar to a hydrogen atom. This system is hence called a gravitational atom, in analogy with the hydrogen atom. Similar to the emission of electromagnetic waves during an electronic transition, one should expect the emission of gravitational waves during a bosonic transition. This thesis is dedicated to the formation of these scalar clouds and this exotic gravitational-wave signature.