Preheating in an inflationary model with disformal coupling

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, the emergence of novel derivative interactions mixing the kinetic terms of the fields is natural. We start by deriving the evolution of the background system and then quantify how the disformal coupling influences inflationary trajectory. 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 standard Mathieu equation. Interestingly in our analysis, we discover that broad resonances can be typically achieved and are potentially efficient causing the particle number density in this process to exponentially increase.