New Mass Window for Primordial Black Holes as Dark Matter from Memory Burden Effect

TL;DR

This paper explores how quantum memory effects can extend primordial black hole lifetimes, relaxing previous constraints and opening new mass windows for PBHs to be viable dark matter candidates.

Contribution

It introduces the impact of memory burden effects on PBH evaporation, showing that these effects can extend black hole lifetimes and alter existing dark matter constraints.

Findings

Memory burden effects slow down PBH evaporation.

Extended PBH lifetimes relax previous mass constraints.

PBHs lighter than 10^9g can still be dark matter candidates.

Abstract

The mass ranges allowed for Primordial Black Holes (PBHs) to constitute all of Dark Matter (DM) are broadly constrained. However, these constraints rely on the standard semiclassical approximation which assumes that the evaporation process is self-similar. Quantum effects such as memory burden take the evaporation process out of the semiclassical regime latest by half-decay time. What happens beyond this time is currently not known. However, theoretical evidence based on prototype models indicates that the evaporation slows down thereby extending the lifetime of a black hole. This modifies the mass ranges constrained, in particular, by BBN and CMB spectral distortions. We show that previous constraints are largely relaxed when the PBH lifetime is extended, making it possible for PBHs to constitute all of DM in previously excluded mass ranges. In particular, this is the case for PBHs lighter than $10^9$g which enter the memory burden stage before BBN and are still present today as DM.