Early clustering of DM particles around PBHs Density profiles and signatures

Primordial black holes may have been produced in the early stages of the universe, after cosmic inflation. If so, dark matter in the form of elementary particles can be subsequently accreted around these objects, in particular when it gets non-relativistic and further streams freely in the primordial plasma. A dark matter mini-spike builds up gradually around each black hole during the radiation dominated era, with density orders of magnitude larger than the cosmological one. The radial profiles of mini-spikes depend sensitively on black hole mass, dark matter particle mass and temperature of kinetic decoupling. They exhibit a rich variety of behaviors which are presented here. These spikes subsequently annihilate and leave potentially detectable signatures in the extragalactic γ-ray background and in the cosmic microwave background.