Memory burden effect of regular primordial black holes

TL;DR

This paper investigates how the memory burden effect combined with regular black hole models can extend the viable mass range of primordial black holes as dark matter candidates, relaxing previous evaporation constraints.

Contribution

It introduces the combined impact of the memory burden effect with regular black hole metrics on primordial black hole evaporation, revealing new dark matter mass windows.

Findings

Memory burden effect significantly relaxes evaporation constraints.

A new PBH mass window at 10^6–10^8 g opens for dark matter.

Regular PBHs can constitute all dark matter without violating nucleosynthesis bounds.

Abstract

Primordial black holes (PBHs) have attracted intensive research interest as a promising candidate of dark matter. However, because of the Hawking radiation, the PBHs lighter than $10^{15}~\rm{g}$ have already evaporated before today. To extend the PBH mass window to small-mass range, two possible ingredients are explored. The first is the consideration of regular PBHs with non-singular metrics, which can decrease the Hawking temperature, thereby lowering black hole evaporation. The second is the incorporation of the memory burden (MB) effect, which can further suppress the evaporation rate, after regular PBHs have lost a certain amount of their initial masses. In this work, we combine these two ingredients and study the MB effects of three types of regular PBHs (the Hayward, Bardeen and Simpson--Visser black holes). Assuming a phenomenological self-similar evaporation, we find that the MB effect significantly relaxes the evaporation constraints. For a benchmark of the MB strength parameter $k=1$, a new PBH mass window opens at around $10^6$--$10^8$ g, where regular PBHs can compose all dark matter without violating the Big Bang nucleosynthesis bounds.