Generic estimates for magnetic fields generated during inflation including Dirac-Born-Infeld theories

TL;DR

This paper provides a general estimation of large-scale magnetic fields generated during inflation within Dirac-Born-Infeld theories, highlighting conditions for sufficient seed fields to explain galactic magnetism.

Contribution

It introduces a broad framework for estimating inflationary magnetic fields in DBI theories, accounting for the speed of sound and conformal symmetry breaking effects.

Findings

Magnetic fields can be amplified in ultra-relativistic regimes of DBI theories.

Conditions for seed magnetic fields to satisfy observational bounds are clarified.

The framework covers most conformal symmetry breaking models with electromagnetic coupling.

Abstract

We estimate the strength of large-scale magnetic fields produced during inflation in the framework of Dirac-Born-Infeld (DBI) theories. This analysis is sufficiently general in the sense that it covers most of conformal symmetry breaking theories in which the electromagnetic field is coupled to a scalar field. In DBI theories there is an additional factor associated with the speed of sound, which allows a possibility to lead to an extra amplification of the magnetic field in a ultra-relativistic region. We clarify the conditions under which seed magnetic fields to feed the galactic dynamo mechanism at a decoupling epoch as well as present magnetic fields on galactic scales are sufficiently generated to satisfy observational bounds.