Primordial black holes: formation, spin and type II

TL;DR

This review discusses the formation, initial spin, and evolution of primordial black holes generated during the inflationary era, emphasizing their dynamics in radiation and matter-dominated phases.

Contribution

It provides a comprehensive overview of PBH formation mechanisms, initial spin estimation, and fluctuation evolution during different cosmological phases.

Findings

PBHs can form from large cosmological perturbations during inflation.

Initial spins of PBHs depend on the formation conditions and dynamics.

Type II fluctuations evolve distinctly in radiation and matter-dominated eras.

Abstract

Primordial black holes (PBHs) may have formed through the gravitational collapse of cosmological perturbations that were generated and stretched during the inflationary era, later entering the cosmological horizon during the decelerating phase, if their amplitudes were sufficiently large. In this review paper, we will briefly introduce the basic concept of PBHs and review the formation dynamics through this mechanism, the estimation of the initial spins of PBHs and the time evolution of type II fluctuations, with a focus on the radiation-dominated and (early) matter-dominated phases.