Inflation with antisymmetric tensor field: new candidates

TL;DR

This paper explores inflation models driven by antisymmetric tensor fields with minimal and nonminimal gravity couplings, demonstrating new viable scenarios and analyzing their perturbation spectra, including tensor modes and gravitational wave speeds.

Contribution

It introduces novel inflation models with antisymmetric tensor fields, showing inflation viability with different background choices and analyzing tensor perturbations and gravitational wave properties.

Findings

Inflation supported with minimal quadratic potential using new background structure.

Nonminimal coupling allows tuning of gravitational wave speed to c.

Highly scale-dependent power spectrum in quartic potential model.

Abstract

We study classes of inflation models driven by antisymmetric tensor field, with minimal and nonminimal couplings to gravity, that address known issues of such models considered in the past. First we show that with a different choice of the background structure of 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 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 perturbed metric are found to evolve differently in this model, and give rise to a highly scale-dependent power spectrum.