Primordial Kerr Black Holes

TL;DR

This paper reviews the constraints on primordial Kerr black holes as dark matter candidates, focusing on Hawking evaporation, spin limits, gamma-ray backgrounds, and the potential link to Planet 9.

Contribution

It extends Hawking evaporation limits to Kerr black holes and analyzes how spin affects the dark matter window for primordial black holes.

Findings

Spin significantly influences the dark matter viability of PBHs.

Gamma-ray background constraints depend on PBH spin.

Planet 9 could potentially be a primordial black hole.

Abstract

Primordial Black Holes (PBHs) are appealing candidates for dark matter in the universe but are severely constrained by theoretical and observational constraints. We will focus on the Hawking evaporation limits extended to Kerr black holes. In particular, we will discuss the possibility to distinguish between black holes of primordial and of stellar origins based on the Thorne limit on their spin. We will also review the isotropic extragalactic gamma ray background constraints and show that the ``window'' in which PBHs can constitute all of the dark matter depends strongly on the PBH spin. Finally, we will consider the possibility that the so-called Planet 9 is a primordial black hole.