Magnetogenesis From Baryon Asymmetry During an Early Matter Dominated Era

TL;DR

This paper investigates how an early matter-dominated era influences the evolution of baryon asymmetry and hypermagnetic fields, revealing that non-standard cosmological histories can significantly alter these processes and their outcomes.

Contribution

It demonstrates that a non-standard early universe cosmology can drastically change the evolution of baryon asymmetry and hypermagnetic fields, affecting their amplification and survival.

Findings

Baryon asymmetry and hypermagnetic field amplitudes can vary by orders of magnitude under different cosmological histories.

The timing of weak sphaleron activation is sensitive to the Hubble rate during early universe.

The potential for hypermagnetic fields to amplify and preserve baryon asymmetry depends on the cosmological evolution.

Abstract

In this paper, we study the simultaneous evolution of baryon asymmetry and hypermagnetic field amplitude assuming an early matter domination. We contrast our results to the conventional case where radiation domination during early universe is assumed. We show that the baryon asymmetry and the hypermagntic field amplitude can change by orders of magnitude if we assume a non-standard history of cosmology. That is because the Hubble rate determines which processes are efficient. We find that a change in Hubble rate can have a significant impact on when the weak sphalerons become active. As a result of a change in the evolution of baryonic asymmetry, alters the evolution of hypermagnetic field amplitude. It is known that if the hypermagnetic field amplitude is large enough, it can save the baryon asymmetry from diminishing. We show that whether a small seed of hypermagnetic field amplitude can be amplified to a large enough value will strongly depend on the history of cosmology.