Primordial Black Hole Baryogenesis

TL;DR

This paper explores whether primordial black hole evaporation can explain the universe's baryon asymmetry and dark matter, finding it unlikely unless CP violation is unusually large, but remains compatible with certain cosmological models.

Contribution

It provides a simple derivation showing the baryon asymmetry's insensitivity to initial conditions and explores the viability of black hole remnants as dark matter.

Findings

Baryon asymmetry is insensitive to initial black hole density.

Black holes cannot explain both baryon asymmetry and dark matter simultaneously under typical CP violation.

Primordial black holes in cyclic models can produce the observed baryon asymmetry.

Abstract

We reconsider the possibility that the observed baryon asymmetry was generated by the evaporation of primordial black holes that dominated the early universe. We present a simple derivation showing that the baryon asymmetry is insensitive to the initial black hole density and the cosmological model but is sensitive to the temperature-dependence of the CP and baryon-violating (or lepton-violating) interactions. We also consider the possibility that black holes stop evaporating and form Planck-mass remnants that act as dark matter. We show that primordial black holes cannot simultaneously account for both the observed baryon asymmetry and the (remnant) dark matter density unless the magnitude of CP violation is much greater than expected from most particle physics models. Finally, we apply these results to ekpyrotic/cyclic models, in which primordial black holes may form when branes collide. We find that obtaining the observed baryon asymmetry is compatible with the other known constraints on parameters.