Density Perturbations in the Universe from Massive Vector Fields

TL;DR

This paper explores how a massive vector field during inflation can produce a scale-invariant spectrum of density perturbations without causing anisotropy, contributing to understanding the origin of cosmic structure.

Contribution

It introduces a mechanism where a massive vector field generates density perturbations during inflation without inducing anisotropy, expanding inflationary perturbation models.

Findings

A scale-invariant superhorizon spectrum of vector perturbations can be generated during inflation.

The curvature perturbation is transferred to the Universe via the curvaton scenario.

Oscillating massive vector fields behave as pressureless isotropic fluids, preventing anisotropy.

Abstract

I discuss the possibility of using a massive vector field to generate the density perturbation in the Universe. I find that a scale-invariant superhorizon spectrum of vector field perturbations is possible to generate during inflation. The associated curvature perturbation is imprinted onto the Universe following the curvaton scenario. The mechanism does not generate a long-range anisotropy because an oscillating massive vector field behaves as a pressureless isotropic fluid.