Primordial magnetic fields in theories of gravity with non-minimal coupling between curvature and matter

TL;DR

This paper explores how non-minimal coupling between curvature and matter in alternative gravity theories can generate primordial magnetic fields during inflation, potentially explaining observed cosmic magnetic fields.

Contribution

It demonstrates that non-minimal gravity models can produce magnetic fields compatible with observations under certain inflationary conditions.

Findings

Magnetic fields generated can match observed large-scale strengths.

Low reheating temperatures favor magnetic field generation.

Non-minimal coupling influences the evolution of primordial magnetic fields.

Abstract

The existence of magnetic fields in the universe is unmistakable. They are observed at all scales from stars to galaxy clusters. However, the origin of these fields remains enigmatic. It is believed that magnetic field seeds may have emerged from inflation, under certain conditions. This possibility is analised in the context of an alternative theory of gravity with non-minimal coupling between curvature and matter. We find, through the solution of the generalised Maxwell equations in the context of non-minimal models, that for general slow-roll inflationary scenarios with low reheating temperatures, $T_{RH}\simeq10^{10}$GeV, the generated magnetic fields can be made compatible with observations at large scales, $\lambda \sim 1 Mpc$.