Inflation with antisymmetric tensor field: new candidates

Abstract

We study classes of inflation models driven by antisymmetric tensor field, with minimal and nonminimal couplings to gravity, that address the known issues of such models considered in the past. First, we show that with a different choice of the background structure of the antisymmetric tensor field, inflation is supported even for the minimal model with quadratic potential contrary to past results. We also include the nonminimal coupling to gravity and analyse perturbations to the antisymmetric tensor as well as the tensor modes of perturbed metric. The two models differ in terms of the behaviour of tensor modes, where the speed of the gravitational wave can be tuned to c in the latter model. The power spectrum and spectral index receive slight scale dependence. Finally, we consider a quartic potential motivated by the graceful exit to reheating phase, which requires a nonminimal coupling to support inflation. The two tensor modes of the perturbed metric are found to evolve differently in this model, and give rise to a highly scale-dependent power spectrum.