Inflationary magnetogenesis with added helicity: constraints from non-gaussianities

TL;DR

This paper evaluates a model of inflationary magnetogenesis with added helicity, analyzing non-Gaussianity constraints to determine its viability in explaining cosmic magnetic fields without strong coupling issues.

Contribution

It provides the first detailed analysis of scalar spectrum and bispectrum corrections in this magnetogenesis model, establishing observational constraints and viability conditions.

Findings

Non-observation of scalar bispectrum constrains the model.

The model can explain magnetic fields if inflation energy scale is below 10^6-10^8 GeV.

Conditions on the auxiliary scalar field's slow roll are necessary for success.

Abstract

In previous work, two of us have proposed a model of inflationary magnetogenesis based on a rolling auxiliary field able both to account for the magnetic fields inferred by the (non) observation of gamma-rays from blazars, and to start the galactic dynamo, without incurring in any strong coupling or strong backreaction regime. Here we evaluate the correction to the scalar spectrum and bispectrum with respect to single-field slow-roll inflation generated in that scenario. The strongest constraints on the model originate from the non-observation of a scalar bispectrum. Nevertheless, even when those constraints are taken into consideration, the scenario can successfully account for the observed magnetic fields as long as the energy scale of inflation is smaller than $10^6\div10^8$~GeV, under some conditions on the slow roll of the auxiliary scalar field.