Helical magnetic fields from Riemann coupling lead to baryogenesis

TL;DR

This paper proposes a novel mechanism where Riemann coupling induces primordial helical magnetic fields that simultaneously lead to baryogenesis, explaining both magnetic fields and matter-antimatter asymmetry in the early universe.

Contribution

It introduces a model with dimension 6 operators involving Riemann coupling that links magnetic field generation to baryogenesis without extending the Standard Model.

Findings

Primordial helical magnetic fields can produce baryon asymmetry.

The model predicts observed baryon asymmetry for realistic reheating temperatures.

The mechanism operates at the beginning of the radiation era.

Abstract

The spectrum of energy density fluctuations, baryon asymmetry, and coherent large-scale magnetic fields are the three observables that provide crucial information on physics at very high energies. Inflation can only provide a mechanism to explain the density perturbations, and the origin of primordial magnetic fields and baryon asymmetry require physics beyond the standard models of cosmology and particle physics. In this work, we show that the mechanism that leads to primordial helical fields also leads to baryogenesis at the beginning of the radiation-dominated epoch. The model we consider here consists of mass dimension 6 operators that include Riemann coupling between gravity and electromagnetic field without extending the Standard Model of particle physics. We explicitly show that the generation of primordial helical magnetic fields leads to baryogenesis. We further show that the model predicts the observed amount of baryon asymmetry of the Universe for a range of reheating temperatures consistent with the observations.