Axion misalignment with memory-burdened PBH

TL;DR

This paper explores how primordial black holes influence axion dark matter production through various misalignment mechanisms, considering advanced effects like kinetic misalignment and backreaction, with implications for detection strategies.

Contribution

It introduces the impact of memory-burden effects and non-standard PBH evaporation regimes on axion DM production, extending beyond semi-classical approximations.

Findings

Axion and PBH parameter space for DM relics is significantly altered.

Different misalignment mechanisms and evaporation regimes affect axion abundance.

Potential detection avenues include gravitational waves and cosmic microwave background observations.

Abstract

We study the possibility of producing axion dark matter (DM) via misalignment mechanisms in a non-standard cosmological era dominated by ultra-light primordial black holes (PBH). While the effect of PBH domination on the production of axion via vacuum misalignment is known assuming the PBH evaporation to proceed according to Hawking's semi-classical (SC) approximation, we go beyond these simplest possibilities to include kinetic misalignment of axion and backreaction effect of emitted particles on the PBH themselves, referred to as the memory-burden (MB) effect. We show that, depending upon the type of misalignment mechanism and PBH evaporation regime, the axion as well as PBH parameter space consistent with the observed DM relic changes significantly having interesting implications for axion detection experiments. PBH also offer complementary detection prospects via gravitational wave due to PBH density fluctuations and excess radiation due to emission of hot axions within reach of future cosmic microwave background experiments.