Parity Violating Statistical Anisotropy

TL;DR

This paper explores how an axial coupling in an Abelian vector boson field can produce scale-invariant, parity-violating signatures in cosmological perturbations, potentially observable in the universe's anisotropy.

Contribution

It derives conditions for scale-invariant, parity-violating particle production in vector fields and applies these to the vector curvaton model with concrete particle theory examples.

Findings

Scale-invariant spectra for vector field transverse components are achievable.

Parity violation in the bispectrum can be generated through axial coupling.

Conditions for observable statistical anisotropy are established.

Abstract

Particle production of an Abelian vector boson field with an axial coupling is investigated. The conditions for the generation of scale invariant spectra for the vector field transverse components are obtained. If the vector field contributes to the curvature perturbation in the Universe, scale-invariant particle production enables it to give rise to statistical anisotropy in the spectrum and bispectrum of cosmological perturbations. The axial coupling allows particle production to be parity violating, which in turn can generate parity violating signatures in the bispectrum. The conditions for parity violation are derived and the observational signatures are obtained in the context of the vector curvaton paradigm. Two concrete examples are presented based on realistic particle theory.