On the coupling of vector fields to the Gauss-Bonnet invariant
  Inflationary models including vector fields have attracted a great deal of
attention over the past decade. Such an interest owes to the fact that they
might contribute to, or even be fully responsible for, the curvature
perturbation imprinted in the cosmic microwave background. However, the
necessary breaking of the vector field's conformal invariance during inflation
is not without problems. In recent years, it has been realized that a number of
instabilities endangering the consistency of the theory arise when the
conformal invariance is broken by means of a non-minimal coupling to gravity.
In this paper, we consider a massive vector field non-minimally coupled to
gravity through the Gauss-Bonnet invariant, and investigate whether the vector
can play the role of a curvaton while evading the emergence of instabilities
and preserves the large-scale isotropy.
