Event

I will discuss the possibility that dark matter is made of weakly interacting, very light scalar particles, briefly reviewing the strong theoretical motivations of this proposal. In a scenario where non-gravitational dark matter interactions are negligible, it is natural to think of black holes as probes because of their very strong gravitational fields. Indeed it is known that an oscillating massive scalar can endow a black hole with hair. In this context, I will show how near-horizon physics can affect the dark matter density at much larger scales. Instead, accounting for the self-gravity of the dark matter cloud, I will study the possibility of ultralight dark matter forming a soliton around the black hole. In this case, I will show that requiring stability of the whole system ensures an important hierarchy of length scales.