Primordial Structure of Massive Black Hole Clusters
Maxim. Yu. Khlopov, Sergei. G. Rubin, Alexander. S. Sakharov
TL;DR
The study addresses the origin of SMBHs in galactic centers and their appearance at high redshift. It introduces a primordial PBH mechanism based on closed domain walls formed from a massless angular mode of a complex scalar during inflation. The angular fluctuations during inflation generate islands of less probable vacuum, leading to closed walls that collapse to PBHs whose masses scale with wall size, yielding a spectrum from subsolar to supermassive and a fractal PBH distribution that seeds galactic nuclei. The model assumes an inflationary Hubble scale around $H=10^{13}$ GeV and remains compatible with BBN and other cosmological constraints. This framework provides a viable primordial channel for creating central massive objects and linking early structure formation to SMBH demographics.
Abstract
We describe a mechanism of the primordial black holes formation that can explain the existence of a population of supermassive black holes in galactic bulges. The mechanism is based on the formation of black holes from closed domain walls. The origin of such domain walls could be a result of the evolution of an effectively massless scalar field during inflation. The initial non-equilibrium distribution of the scalar field imposed by background de-Sitter fluctuations gives rise to the spectrum of black holes, which covers a wide range of masses -- from superheavy ones down to deeply subsolar. The primordial black holes of smaller masses are concentrated around the most massive ones within a fractal-like cluster.