The clustering dynamics of primordial black boles in $N$-body simulations

Understand

We explore the possibility that Dark Matter (DM) may be explained by a non-uniform background of approximately stellar-mass clusters of Primordial Black Holes (PBHs), by simulating the evolution them from recombination to the present with over 5000 realisations using a Newtonian $ N $-body code.

• We compute the cluster rate of evaporation, and extract the binary and merged sub-populations along with their parent and merger tree histories, lifetimes and formation rates; the dynamical and orbital parameter profiles, the degree of mass segregation and dynamical friction, and power spectrum of close encounters.
• Overall, we find that PBHs can constitute a viable DM candidate, and that their clustering presents a rich phenomenology throughout the history of the Universe.
• We show that binary systems constitute about 9.5\% of all PBHs at present, with mass ratios of $ \bar{q}_{\rm B} = 0.154 $, and total masses of $ \bar{m}_{\rm T,\,B} = 303\,M_\odot$.