Statistical anisotropy from inflationary magnetogenesis

TL;DR

This paper investigates how inflationary magnetogenesis can induce mild statistical anisotropy in curvature perturbations, providing new calculations for anisotropic power spectra with evolving gauge couplings and discussing observational constraints.

Contribution

It presents the first computation of curvature power spectra anisotropy with different electric and magnetic gauge coupling evolutions during inflation.

Findings

Weak anisotropy consistent with current data

More stringent bounds on magnetogenesis scenarios

Extension of previous isotropic results to anisotropic cases

Abstract

Provided the quantum fluctuations are amplified in the presence of a classical gauge field configuration the resulting curvature perturbations exhibit a mild statistical anisotropy which should be sufficiently weak not to conflict with current observational data. The curvature power spectra induced by weakly anisotropic initial states are computed here for the first time when the electric and the magnetic gauge couplings evolve at different rates as it happens, for instance, in the relativistic theory of van der Waals interactions. After recovering the results valid for coincident gauge couplings, the constraints imposed by the isotropy and the homogeneity of the initial states are discussed. The obtained bounds turn out to be more stringent than naively expected and cannot be ignored when discussing the underlying magnetogenesis scenarios.