Nonsingular black holes as dark matter

TL;DR

This paper proposes that nonsingular black holes, potentially stabilized by quantum gravity effects, can have finite evaporation temperatures, making them viable dark matter candidates by avoiding traditional evaporation constraints.

Contribution

It introduces a class of nonsingular black holes with finite evaporation temperatures and explores their potential as dark matter, supported by analysis within two-dimensional dilaton gravity.

Findings

Nonsingular black holes can have finite evaporation temperatures.

Remnant masses are proportional to the fundamental length scale.

Slowly evaporating black holes or remnants could serve as dark matter candidates.

Abstract

It is commonly assumed that low-mass primordial black holes cannot constitute a significant fraction of the dark matter in our universe due to their predicted short lifetimes from the conventional Hawking radiation and evaporation process. Assuming physical black holes are nonsingular--likely due to quantum gravity or other high-energy physics--we demonstrate that a large class of nonsingular black holes have finite evaporation temperatures. This can lead to slowly evaporating low-mass black holes or to remnant mass states that circumvent traditional evaporation constraints. As a proof of concept, we explore the limiting curvature hypothesis and the evaporation process of a nonsingular black hole solution in two-dimensional dilaton gravity. We identify generic features of the radiation profile and compare them with known regular black holes, such as the Bardeen solution in four dimensions. Remnant masses are proportional to the fundamental length scale, and we argue that slowly evaporating low-mass nonsingular black holes, or remnants, are viable dark matter candidates.