Vector Inflation

TL;DR

The paper proposes vector-field inflation driven by non-minimally coupled massive vector fields, showing that slow-roll dynamics can mimic chaotic scalar-field inflation. Isotropy is achieved either with a triplet of orthogonal vectors or with a large ensemble of randomly oriented vectors, the latter leaving a residual anisotropy of order 1/√N. The authors derive the equations of motion and energy-momentum tensors, estimate the number of e-folds, and demonstrate how inflation ends as the vector amplitudes decay to B ~ 1/√N, with a maximum of about 2π√N e-folds in the random-vector case. The framework generalizes to arbitrary potentials V(B^2) and suggests a path toward unifying inflation with dark energy, contingent on the mass spectrum of the vector fields.

Abstract

We propose a scenario where inflation is driven by non-minimally coupled massive vector fields. In an isotropic homogeneous universe these fields behave in presicely the same way as a massive minimally coupled scalar field. Therefore our model is very similar to the model of chaotic inflation with scalar field. For vector fields the isotropy of expansion is achived either by considering a triplet of orthogonal vector fields or for the expense of $N$ randomly oriented vector fields. In the last case the substantial anisotropy of the expansion of order $1/\sqrt{N}$ survives until the end of inflation. The lightest vector fields might also force the late time acceleration of the Universe.