Preheating in an inflationary model with disformal coupling

Abstract

In this work, we investigate the preheating mechanism in a disformally-coupled inflationary model where the scalar field $\phi$ (which is the inflaton field) naturally coupled to another matter field $\chi$ induced by the disformal transformation. In the present scenario, novel derivative interactions mixing the kinetic terms of the two fields emerge inherently. We start by deriving the evolution of the background system when the back reaction on the background field is neglected. We examine the particle production due to parametric resonances in the models and find in Minkowski space that the stage of parametric resonances can be described by the Mathieu equation. Interestingly, we discover that broad resonances in our models can be typically achieved. Finally, we compare our results with previously studied model with derivative couplings.