Return of the grand unified theory baryogenesis: Source of helical hypermagnetic fields for the baryon asymmetry of the universe

TL;DR

This paper proposes that helical hypermagnetic fields generated via the chiral magnetic effect can enable baryogenesis without $B$-$L$ asymmetry, potentially explaining the universe's baryon asymmetry and linking it to intergalactic magnetic fields.

Contribution

It introduces a mechanism where helical hypermagnetic fields from chiral asymmetry enable baryogenesis without $B$-$L$ asymmetry, challenging previous assumptions.

Findings

Helical hypermagnetic fields can produce baryon asymmetry at electroweak symmetry breaking.

A chiral asymmetry of about 10^{-3} in right-handed electrons can generate the observed baryon asymmetry.

Intergalactic magnetic fields serve as observational evidence supporting this baryogenesis scenario.

Abstract

It has been considered that baryogenesis models without a generation of $B$-$L$ asymmetry such as the GUT baryogenesis do not work since the asymmetry is washed out by the electroweak sphalerons. Here, we point out that helical hypermagnetic fields can be generated through the chiral magnetic effect with a chiral asymmetry generated in such baryogenesis models. The helical hypermagnetic fields then produce baryon asymmetry mainly at the electroweak symmetry breaking, which remains until today. Therefore, the baryogenesis models without $B$-$L$ asymmetry can still be the origin of the present baryon asymmetry. In particular, if it can produce chiral asymmetry mainly carried by right-handed electrons of order of $10^{-3}$ in terms of the chemical potential to temperature ratio, the resultant present-day baryon asymmetry can be consistent with our Universe, although simple realizations of the GUT baryogenesis are hard to satisfy the condition. We also argue the way to overcome the difficulty in the GUT baryogenesis. The intergalactic magnetic fields with $B_0\sim 10^{-16 \sim 17}$ G and $\lambda_0 \sim 10^{-2\sim3}$ pc are the smoking gun of the baryogenesis scenario as discussed before.