Superhorizon Electromagnetic Field Background from Higgs Loops in Inflation

TL;DR

This paper demonstrates that Higgs loops during inflation can generate significant superhorizon electromagnetic fields, providing a novel mechanism for cosmological vector mode generation through scalar-vector interactions.

Contribution

It introduces a loop correction mechanism where Higgs decay into photons during inflation amplifies superhorizon electromagnetic modes, a novel insight into inflationary magnetogenesis.

Findings

Loop corrections dominate over tree-level at superhorizon scales.

Higgs decay into photons seeds large-scale magnetic fields.

Mechanism enables generation of cosmologically relevant vector modes.

Abstract

If Higgs is a spectator scalar, i.e. if it is not directly coupled to the inflaton, superhorizon Higgs modes must have been exited during inflation. Since Higgs is unstable its decay into photons is expected to seed superhorizon photon modes. We use in-in perturbation theory to show that this naive physical expectation is indeed fulfilled via loop effects. Specifically, we calculate the first order Higgs loop correction to the magnetic field power spectrum evaluated at some late time after inflation. It turns out that this loop correction becomes much larger than the tree-level power spectrum at the superhorizon scales. This offers a mechanism to generate cosmologically interesting superhorizon vector modes by scalar-vector interactions.