TDiff-fuelled cosmic magnetic fields

TL;DR

This paper investigates how breaking diffeomorphism invariance to TDiff in electromagnetism affects cosmic magnetic field generation and evolution, providing new insights into their current observable properties.

Contribution

It introduces a novel framework analyzing Diff symmetry breaking to TDiff and its impact on cosmic magnetic fields, including their power spectrum and observational compatibility.

Findings

Diff breaking induces conformal invariance breaking, altering magnetic field evolution.

The model predicts magnetic power spectra consistent with intergalactic magnetic field observations.

Parameter regions are identified where magnetic fields match current observational data.

Abstract

We explore the consequences of the breaking of diffeomorphism (Diff) invariance in the electromagnetic sector. We consider the breaking of Diff symmetry down to the subgroup of transverse diffeomorphisms (TDiff) and analyse its impact on the generation and evolution of cosmic magnetic fields. We show that Diff breaking induces a breaking of conformal invariance that modifies the way in which magnetic fields evolve on super-Hubble scales. The effects of the highly conductive plasma in the evolution are also analysed. We obtain the magnetic power spectrum today and discuss the parameter regions that yield intergalactic magnetic fields compatible with current observations.