Mergers of primordial black holes in extreme clusters and the H0 tension

Abstract

We consider a cosmological model with dark matter in the form of ∼ 10−12M⊙ primordial black holes in dense weakly relativistic clusters with masses 18 − 560M⊙. It is shown that during the multiple collisions of the black holes the ∼ 10% of the initial cluster mass can be transformed into gravitational waves in the time interval from recombination to the redshifts z ≥ 10. At the recombination epoch, the density of matter was larger by ∼ 10% and, accordingly, the universe expansion rate was higher. This leads to a shortening of the sound horizon scale, as is necessary to solve the “H0 tension” problem.