Cosmic magnetic fields from velocity perturbations in the early Universe

TL;DR

This paper demonstrates that velocity perturbations in the early Universe's matter-dominated phase can generate cosmic magnetic fields, which could serve as seed fields for later amplification, with strengths consistent with CMB constraints.

Contribution

It introduces a covariant, gauge-invariant multifluid perturbation scheme showing velocity perturbations can produce seed magnetic fields in the early Universe.

Findings

Generated magnetic fields of 10^{-28} to 10^{-29} G at dynamo onset

Fields are plausible seed candidates for cosmic magnetism

Uses CMB constraints to support field strength estimates

Abstract

We show, using a covariant and gauge-invariant charged multifluid perturbation scheme, that velocity perturbations of the matter-dominated dust Friedmann-Lemaitre-Robertson-Walker (FLRW) model can lead to the generation of cosmic magnetic fields. Moreover, using cosmic microwave background (CMB) constraints, it is argued that these fields can reach strengths of between 10^{-28} and 10^{-29} G at the time the dynamo mechanism sets in, making them plausible seed field candidates.