Slow-roll inflation from massive vector fields non-minimally coupled to gravity

TL;DR

This paper explores slow-roll inflation driven by massive vector fields non-minimally coupled to gravity, identifying conditions under which inflation can occur despite challenges posed by the vector field's effective mass.

Contribution

It introduces a vector-tensor inflation model with arbitrary non-minimal couplings and demonstrates how suitable parameter choices enable slow-roll inflation.

Findings

A regime with slow-roll inflation was achieved.

The vector field can behave as a constant driving quasi de Sitter expansion.

Inflation is possible with appropriate parameter constraints.

Abstract

In this work we study slow-roll inflation for a vector-tensor model with massive vector fields non-minimally coupled to gravity. The model under consideration has arbitrary parameters for each geometrical coupling. Taking into account a spatially flat FRW type universe and a general vector fields (with temporal and spatial components), we get the general expressions for equation of motion and the total energy momentum tensor. In this scenario, the isotropy of expansion is guaranteed considering a triplet of orthogonal vector fields, but the effective mass of the vector field is of the order of the Hubble scale and the inflationary regime is difficult to realize with this model. However, for suitable values (or constraints) of model parameters, it is possible to overcome this issue. In this sense, two cases were analyzed. In the first case, a regime with slow-roll inflation was obtained, and for the second case the vector field behaves as a constant, and it drives a quasi de Sitter expansion, hence that slow-roll takes place and inflation occurs.