Primordial Black Holes

TL;DR

Primordial black holes (PBHs) serve as key probes of early Universe physics, with their formation mechanisms and observational constraints informing models of cosmology, particle physics, and galaxy formation.

Contribution

This paper reviews PBH formation mechanisms, observational constraints, and proposes a novel approach to galaxy formation involving primordial black hole clouds.

Findings

Constraints on PBH spectrum restrict particle physics models.

PBH evaporation effects limit early Universe scenarios.

Closed wall contraction offers a new galaxy formation pathway.

Abstract

Primordial black holes (PBHs) are a profound signature of primordial cosmological structures and provide a theoretical tool to study nontrivial physics of the early Universe. The mechanisms of PBH formation are discussed and observational constraints on the PBH spectrum, or effects of PBH evaporation, are shown to restrict a wide range of particle physics models, predicting an enhancement of the ultraviolet part of the spectrum of density perturbations, early dust-like stages, first order phase transitions and stages of superheavy metastable particle dominance in the early Universe. The mechanism of closed wall contraction can lead, in the inflationary Universe, to a new approach to galaxy formation, involving primordial clouds of massive BHs created around the intermediate mass or supermassive BH and playing the role of galactic seeds.