Late cosmic acceleration in a vector-Gauss–Bonnet gravity model

Abstract

In this work, we study a general vector–tensor model of dark energy (DE) with a Gauss–Bonnet term coupled to a vector field and without explicit potential terms. Considering a spatially flat Friedmann–Robertson–Walker (FRW) type universe and a vector field without spatial components, the cosmological evolution is analyzed from the field equations of this model considering two sets of parameters. In this context, we have shown that it is possible to obtain an accelerated expansion phase of the universe since the equation state parameter [Formula: see text] satisfies the restriction [Formula: see text] (for suitable values of model parameters). Further, analytical expressions for the Hubble parameter [Formula: see text], equation state parameter [Formula: see text] and the invariant scalar [Formula: see text] are obtained. We also find that the square of the speed of sound is negative for all values of redshift, therefore, the model presented here shows a sign of instability under small perturbations. We finally perform an analysis using [Formula: see text] observational data and we find that for the free parameter [Formula: see text] in the interval [Formula: see text], at 99.73% C.L. (and fixing [Formula: see text] and [Formula: see text]), the model has a good fit to the data.