Hilltop inflation and generation of helical magnetic field

TL;DR

This paper proposes a novel mechanism for primordial magnetic field generation during hilltop inflation via anomaly cancellation in quantum electrodynamics, resulting in a helical, scale-dependent magnetic spectrum with potential cosmological relevance.

Contribution

It introduces a new origin for primordial magnetic fields through anomaly cancellation in hilltop inflation, highlighting the helical nature and scale dependence of the generated magnetic spectrum.

Findings

Magnetic field spectrum is helical and scale-dependent.

Significant magnetic field strength can be produced in a large parameter space.

The model provides a viable source for present-day intergalactic magnetic fields.

Abstract

Primordial magnetic field generated in the inflationary era can act as a viable source for the present day intergalactic magnetic field of sufficient strength. We present a fundamental origin for such a primordial generation of the magnetic field, namely through anomaly cancellation of $U(1)$ gauge field in quantum electrodynamics in the context of hilltop inflation. We have analysed at length the power spectrum of the magnetic field, thus generated, which turns out to be helical in nature. We have also found that magnetic power spectrum has significant scale-dependence giving rise to a non-trivial magnetic spectral index, a key feature of this model. Interestingly, there exists a large parameter space, where magnetic field of significant strength can be produced.