Primordial black hole evaporation in a thermal bath and gravitational waves

TL;DR

This paper explores how the thermal environment of primordial black holes in the early Universe affects their evaporation process and the resulting gravitational wave signals, providing a more realistic model for their observational signatures.

Contribution

It introduces a thermal evaporation framework for primordial black holes, accounting for environmental effects on decay rates and gravitational wave production, which was neglected in prior studies.

Findings

Thermal effects significantly alter PBH evaporation timelines.

Enhanced graviton emission modifies gravitational wave spectra.

Provides a new framework for predicting gravitational wave signatures from PBHs.

Abstract

Primordial black holes (PBHs) formed in the early Universe evaporate via Hawking radiation and constitute a generic source of stochastic gravitational waves. Existing studies of gravitational wave production from evaporating PBHs typically assume vacuum evaporation, neglecting the fact that PBHs in the early Universe are embedded in a hot thermal plasma. In this work, we investigate gravitational wave production from primordial black holes whose evaporation is thermally influenced by their surrounding environment. We adopt a thermal evaporation framework in which interactions with the ambient plasma modify the effective decay rate of the black hole, leading to enhanced mass loss at early times and a redistribution of the evaporation history compared to the standard non-thermal vacuum case. Since graviton emission is intrinsically tied to the evaporation history of PBHs, these thermal effects play a crucial role in determining the timing and spectral properties of the resulting stochastic gravitational wave background. Our results provide a consistent framework for incorporating thermal effects into gravitational wave production from evaporating primordial black holes and set the stage for a detailed analysis of their observational signatures.