Small-scale structure of primordial black hole dark matter and its implications for accretion

Understand

Primordial black hole (PBH) dark matter (DM) nonlinear small-scale structure formation begins before the epoch of recombination due to large Poisson density fluctuations.

• Those small-scale effects still survive today, distinguishing physics of PBH DM structure formation from the one involving WIMP DM.
• We construct an analytic model for the small-scale PBH velocities that reproduces the velocity floor seen in numerical simulations, and investigate how these motions impact PBH accretion bounds at different redshifts.
• We find that the effect is small at the time of recombination, leaving the cosmic microwave background bounds on PBH abundance unchanged.