Probing Ultralight Bosons around Black Holes with Numerical Relativity

Abstract

One of the greatest mysteries of our current understanding of the Universe is the nature ofdark matter. There are several dark matter candidates of various masses but a prominent typeof dark matter isaxion dark matter. In this thesis we study a type of axion dark matter knownasUltralight Bosonswith numerical relativity. These particles are thought to form cloudsaround black holes through thesuperradiance process. The main novelty of this thesis is thatwe may investigate the effects of clouds of ultralight bosons around black holes numericallyin a regime unexplored by perturbative methods. For our numerical setup we utilize a C++library called KADATH to solve the initial value problem in the XCTS approach. We perform avariety of tests of the code robustness and solve numerical degeneracy problems at the blackhole horizon. Finally, we obtain results of the free bosonic field profile around the black hole.Furthermore, we obtain results of new physical effects from the inclusion of self-interactionsand backreaction.