Generation of Cosmological Seed Magnetic Fields from Inflation with Cutoff

TL;DR

This paper proposes a novel inflationary mechanism involving a minimal length cutoff that breaks conformal invariance, enabling the generation of seed magnetic fields sufficient for galactic magnetism without dynamo amplification.

Contribution

It introduces a model where a minimal length scale during inflation effectively gives photons a large negative mass, leading to electromagnetic field amplification.

Findings

Seed magnetic fields can be generated during inflation with a minimal length cutoff.

The mechanism produces magnetic fields strong enough for galactic magnetism without dynamo.

The effective photon mass is negligible in later universe epochs.

Abstract

Inflation has the potential to seed the galactic magnetic fields observed today. However, there is an obstacle to the amplification of the quantum fluctuations of the electromagnetic field during inflation: namely the conformal invariance of electromagnetic theory on a conformally flat underlying geometry. As the existence of a preferred minimal length breaks the conformal invariance of the background geometry, it is plausible that this effect could generate some electromagnetic field amplification. We show that this scenario is equivalent to endowing the photon with a large negative mass during inflation. This effective mass is negligibly small in a radiation and matter dominated universe. Depending on the value of the free parameter of the theory, we show that the seed required by the dynamo mechanism can be generated. We also show that this mechanism can produce the requisite galactic magnetic field without resorting to a dynamo mechanism.