Supergravity inspired Vector Curvaton

TL;DR

This paper explores how a massive Abelian vector field with a growing gauge kinetic function during inflation can generate the Universe's curvature perturbation, acting as a vector curvaton with specific conditions on its mass and reheating.

Contribution

It demonstrates the viability of a vector curvaton mechanism with a scale-invariant spectrum, including conditions on mass increase and reheating modulation.

Findings

Vector field can produce a scale-invariant superhorizon spectrum.

Vector curvaton can generate observed curvature perturbation.

Mass increase at TeV-scale phase transition is feasible.

Abstract

It is investigated whether a massive Abelian vector field, whose gauge kinetic function is growing during inflation, can be responsible for the generation of the curvature perturbation in the Universe. Particle production is studied and it is shown that the vector field can obtain a scale invariant superhorizon spectrum of perturbations with a reasonable choice of kinetic function. After inflation the vector field begins coherent oscillations, during which it corresponds to pressureless isotropic matter. When the vector field dominates the Universe its perturbations give rise to the observed curvature perturbation following the curvaton scenario. It is found that this is possible if, after the end of inflation, the mass of the vector field increases at a phase transition at temperature of order 1 TeV or lower. Inhomogeneous reheating, whereby the vector field modulates the decay rate of the inflaton, is also studied.