Stochastic inflation in a simple two-field model.

Abstract

The dynamics of a nondominating scalar field during inflation is considered in the framework of the stochastic approach where its motion and that of the inflaton are described by two coupled Langevin equations. Curvature perturbations induced by the inflaton make the problem that of a Brownian motion in a random medium. The associated Fokker-Planck equation is solved for a free massless field in a power-law inflation driven by an inflaton with an exponential potential : this simple model could describe the dynamics of the axion, or any other pseudo Goldstone boson, during inflation