Angular Momentum of Dark Matter Black Holes

TL;DR

This paper discusses the angular momentum of dark matter black holes, emphasizing its importance in understanding detection constraints and suggesting most are primordial rather than stellar in origin.

Contribution

It highlights the significance of black hole angular momentum in dark matter detection and revises previous bounds considering non-zero J.

Findings

Bounds from CMB distortion are too strict for rotating black holes.

Most dark matter black holes are primordial, not from stellar collapse.

Angular momentum plays a crucial role in black hole detection constraints.

Abstract

The putative black holes which may constitute all the dark matter are described by a Kerr metric with only two parameters, mass M and angular momentum J. There has been little discussion of J since it plays no role in the upcoming attempt at detection by microlensing. Nevertheless J does play a central role in understanding the previous lack of detection, especially of CMB distortion. We explain why bounds previously derived from lack of CMB distortion are too strong for primordial black holes with J non-vanishing. Almost none of the dark matter black holes can be from stellar collapse, and nearly all are primordial, to avoid excessive CMB distortion.