Spin of primordial black holes in the model with collapsing domain walls

TL;DR

This paper studies how primordial black holes acquire spin during collapse of domain walls in the early universe, revealing mass-dependent spin outcomes and potential additional spin from vector perturbations.

Contribution

It introduces a model for spin acquisition of primordial black holes during domain wall collapse, highlighting mass-dependent spin values and the influence of vector perturbations.

Findings

Black holes with mass > 10^{-3} M_sun have small spins (a_S<1).

Less massive black holes can have near-extreme spins (a_S≈1).

Vector mode perturbations may add to the black holes' spin.

Abstract

The angular momentum (spin) acquisition by a collapsing domain wall at the cosmological radiation-dominated stage is investigated. During the collapses, primordial black holes and their clusters can be born in various mass ranges. Spin accumulation occurs under the influence of tidal gravitational perturbations from the surrounding density inhomogeneities at the epoch when the domain wall crosses the cosmological horizon. It is shown that the dimensionless spin parameter can have the small values $a_S<1$ only for primordial black holes with masses $M>10^{-3}M_\odot$, whereas less massive black holes receive extreme spins $a_S\simeq1$. It is possible that primordial black holes obtain an additional spin due to the vector mode of perturbations.