The Merger Rate of Black Holes in a Primordial Black Hole Cluster

TL;DR

This paper investigates the merger rate of primordial black holes within clusters resembling globular clusters, revealing that active merging has largely ceased over the cluster's evolution.

Contribution

It provides a detailed analysis of how the merger rate of primordial black holes evolves in clusters with a broad mass spectrum and a central massive black hole.

Findings

Merger rate significantly changes during cluster evolution.

Clusters have passed the active merging stage.

Black hole mergers are less frequent now.

Abstract

In this paper, the merger rate of black holes in a cluster of primordial black holes (PBHs) is investigated. The clusters have characteristics close to those of typical globular star clusters. A cluster that has a wide mass spectrum ranging from $10^{-2}$ to $10 \, M_{\odot}$ (Solar mass) and contains a massive central black hole of the mass $M_{\bullet} = 10^3 \, M_{\odot}$ is considered. It is shown that in the process of the evolution of cluster, the merger rate changed significantly, and by now, the PBH clusters have passed the stage of active merging of the black holes inside~them.