Vector Field Models of Inflation and Dark Energy

TL;DR

This paper explores various vector field models as alternatives to scalar fields for explaining inflation and dark energy, analyzing their compatibility with cosmological observations and their dynamical properties.

Contribution

It introduces new classes of vector field models, including spatial and time-like fields, and demonstrates their viability and dynamical behavior in cosmological contexts.

Findings

Spatial vector fields can be compatible with anisotropy bounds under certain conditions.

Time-like vector fields can be compatible with isotropy and influence cosmic evolution with non-minimal couplings.

A vector-Gauss-Bonnet model reproduces late-time acceleration and early inflation.

Abstract

We consider several new classes of viable vector field alternatives to the inflaton and quintessence scalar fields. Spatial vector fields are shown to be compatible with the cosmological anisotropy bounds if only slightly displaced from the potential minimum while dominant, or if driving an anisotropic expansion with nearly vanishing quadropole today. The Bianchi I model with a spatial field and an isotropic fluid is studied as a dynamical system, and several types of scaling solutions are found. On the other hand, time-like fields are automatically compatible with large-scale isotropy. We show that they can be dynamically important if non-minimal gravity couplings are taken into account. As an example, we reconstruct a vector-Gauss-Bonnet model which generates the concordance model acceleration at late times and supports an inflationary epoch at high curvatures. The evolution of vortical perturbations is considered.