Electroweak baryogenesis by primordial black holes in Brans-Dicke modified gravity

TL;DR

This paper proposes a novel electroweak baryogenesis mechanism in Brans-Dicke modified gravity involving primordial black holes, Hawking radiation, and domain walls, which can produce the observed baryon asymmetry without requiring a first order phase transition.

Contribution

It introduces a new baryogenesis scenario in Brans-Dicke cosmology utilizing primordial black holes and Hawking radiation, avoiding the need for a first order phase transition.

Findings

Black holes can dominate the universe's energy density, extending their lifetime.

The mechanism can produce the observed baryon asymmetry with realistic CP-violation angles.

The scenario is more efficient than in standard FRW cosmology.

Abstract

A successful baryogenesis mechanism is proposed in the cosmological framework of Brans-Dicke modified gravity. Primordial black holes with small mass are produced at the end of the Brans-Dicke field domination era. The Hawking radiation reheats a spherical region around every black hole to a high temperature and the electroweak symmetry is restored there. A domain wall is formed separating the region with the symmetric vacuum from the asymmetric region where electroweak baryogenesis takes place. First order phase transition is not needed. In Brans-Dicke cosmologies black hole accretion can be strong enough to lead to black holes domination which extends the lifetime of black holes and therefore baryogenesis. The analysis of the whole scenario, finally, results in the observed baryon number which can be achieved for a CP-violation angle that is predicted by observationally accepted Two-Higgs Doublet Models. The advantage of our proposed scenario is that naturally provides both black hole domination and more efficient baryogenesis for smaller CP violating angles compared to the same mechanism applied in a FRW cosmological background.