Formation of Primordial Black Hole Clusters from Phase Transitions in the Early Universe

Abstract

A new model of the formation of primordial black holes (PBHs) is considered. The PBH generation mechanism is based on the collapse of massive walls formed in a scalar field during second-order phase transitions caused by quantum fluctuations during inflation. An essential feature of the mechanism is the formation of primordial black holes in the form of clusters. An analytical spectrum of PBH masses is obtained. We also demonstrate the possibility of forming the clusters with a total mass of ∼ 10⁵–10⁸M_☉, ∼ 1 pc in size, and ∼ 10¹¹ in number, which corresponds to the observational data on the number of galaxies in the visible region of the Universe. The prospect for the use of the proposed approach as a new scenario of the formation of galactic nuclei in the early Universe is shown.