Assessing the tension between a black hole dominated early universe and leptogenesis

TL;DR

This paper investigates how primordial black holes influence leptogenesis and baryon asymmetry, showing that black hole evaporation partially offsets thermal leptogenesis, challenging its viability in certain mass regimes.

Contribution

First numerical analysis of the interplay between black hole evaporation and thermal leptogenesis, highlighting limitations in explaining baryon asymmetry with primordial black holes.

Findings

Black hole evaporation partially mitigates entropy dilution of leptogenesis.

Intermediate-mass right-handed neutrinos cannot fully explain baryon asymmetry in black hole dominated scenarios.

Gravitational wave detection from primordial black holes could challenge thermal leptogenesis models.

Abstract

We perform the first numerical calculation of the interplay between thermal and black hole induced leptogenesis, demonstrating that the right-handed neutrino surplus produced during the evaporation only partially mitigates the entropy dilution suffered by the thermal component. As such, the intermediate-mass regime of the right-handed neutrinos, $10^6{\rm~GeV} \lesssim M_{N} \lesssim 10^{9}{\rm~GeV}$, could not explain the observed baryon asymmetry even for fine-tuned scenarios if there existed a primordial black hole dominated era, consistent with initial black hole masses of $M_i \gtrsim \mathcal{O}\left(1\right)$ kg. Detection of the gravitational waves emitted from the same primordial black holes would place intermediate-scale thermal leptogenesis under tension.