Clustering of Primordial Black Holes. II. Evolution of Bound Systems

TL;DR

This paper investigates how primordial black holes cluster and form bound systems early in the universe, potentially leading to mergers before Hawking evaporation, impacting dark matter models.

Contribution

It introduces a detailed analysis of the formation and evolution of bound primordial black hole systems during the radiation-dominated era.

Findings

Primordial black hole clustering leads to early bound system formation.

Bound systems can cause PBH mergers before evaporation.

Clustering affects constraints on PBH dark matter.

Abstract

Primordial Black Holes (PBHs) that form from the collapse of density perturbations are more clustered than the underlying density field. In a previous paper, we showed the constraints that this has on the prospects of PBH dark matter. In this paper we examine another consequence of this clustering: the formation of bound systems of PBHs in the early universe. These would hypothetically be the earliest gravitationally collapsed structures, forming when the universe is still radiation dominated. Depending upon the size and occupation of the clusters, PBH merging occurs before they would have otherwise evaporated due to Hawking evaporation.