Large-scale magnetic fields from inflation in teleparallel gravity

TL;DR

This paper explores how large-scale magnetic fields can be generated during inflation within teleparallel gravity by coupling the electromagnetic field to the torsion scalar, potentially explaining observed cosmic magnetic fields.

Contribution

It introduces a novel mechanism for magnetic field generation during inflation using teleparallelism, differing from traditional curvature-based gravity theories.

Findings

Magnetic fields of ~10^{-9} G on 1 Mpc scale can be produced

Power-law coupling of electromagnetic field to torsion scalar is effective

Backreaction and strong coupling issues are not addressed in this model

Abstract

Generation of large-scale magnetic fields in inflationary cosmology is studied in teleparallelism, where instead of the scalar curvature in general relativity, the torsion scalar describes the gravity theory. In particular, we investigate a coupling of the electromagnetic field to the torsion scalar during inflation, which leads to the breaking of conformal invariance of the electromagnetic field. We demonstrate that for a power-law type coupling, the current magnetic field strength of $\sim 10^{-9}$ G on 1 Mpc scale can be generated, if the backreaction effects and strong coupling problem are not taken into consideration.