Extremal Kerr Black Hole Dark Matter from Hawking Evaporation

TL;DR

This paper shows that primordial black holes can evolve into extremal Kerr black holes through Hawking evaporation, potentially constituting all dark matter due to their stability and low interaction probability.

Contribution

It introduces a stochastic model of black hole evolution demonstrating the formation of extremal Kerr black holes from primordial origins, with implications for dark matter composition.

Findings

A significant fraction of primordial black holes become extremal Kerr black holes.

Extremal Kerr black holes have low probability of absorbing cosmic particles.

EKBHs could account for all dark matter if initially abundant.

Abstract

The Hawking process results in a monotonic decrease of the black hole mass, but a biased random walk of the black hole angular momentum. We demonstrate that this stochastic process leads to a significant fraction of primordial black holes becoming extremal Kerr black holes (EKBHs) of one to a few Planck masses regardless of their initial mass. For these EKBHs, the probability of ever absorbing a photon or other particle from the cosmic environment is small, even in the cores of galaxies. Assuming that EKBHs are stable, they behave as cold dark matter, and can comprise all of the dark matter if they are formed with the correct initial abundance.