Inflation with antisymmetric tensor field: new candidates

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.

Automated summary

This study investigates classes of inflation models driven by antisymmetric tensor field, with minimal and nonminimal couplings to gravity, and proposes solutions to known issues of such models. The study shows that by choosing a different background structure for the antisymmetric tensor field, inflation can still be supported in the minimal model with a quadratic potential, contrary to previous results. The study also analyzes the impact of nonminimal coupling to gravity on perturbations to the antisymmetric tensor and the tensor modes of perturbed metric. Furthermore, the study explores the behavior of tensor modes in the two models, finding that the speed of gravitational waves can be tuned to c in the latter model. The power spectrum and spectral index exhibit slight scale dependence. Finally, the study considers a quartic potential motivated by the graceful exit to the reheating phase, which requires a nonminimal coupling to support inflation. The evolution of the two tensor modes of the perturbed metric differs in this model, resulting in a highly scale-dependent power spectrum.