Spinning primordial black holes formed during a matter-dominated era

TL;DR

This paper investigates the formation and evolution of spinning primordial black holes during an early matter-dominated era using advanced simulations, revealing that their final spin is likely negligible unless the matter era is very short.

Contribution

It provides the first detailed non-linear relativistic simulations of spinning primordial black hole formation during a matter era, quantifying mass and angular momentum transfer.

Findings

Mass transfer efficiency is about 10%.

Angular momentum transfer efficiency is about 5%.

Final black hole spin is negligible unless the matter era is very short.

Abstract

We study the formation of spinning primordial black holes during an early matter-dominated era. Using non-linear 3+1D general relativistic simulations, we compute the efficiency of mass and angular momentum transfer in the process -- which we find to be $\mathcal{O}(10\%)$ and $\mathcal{O}(5\%)$, respectively. We show that subsequent evolution is important due to the seed PBH accreting non-rotating matter from the background, which decreases the dimensionless spin. Unless the matter era is short, we argue that the final dimensionless spin will be negligible.