Perturbative Dissipation in Minimal Warm Inflation

Abstract

We present an analysis of the perturbative modes of dissipation in the minimal warm inflation model where an axion-inflaton is coupled to a gluon thermal bath through the axion-gauge coupling. The corresponding friction coefficient, which generically is governed by IR physics, for the processes we consider is dominated by Landau damping of soft space-like gluons and the plasmon decay of hard on shell gluons. Since both of these processes are IR dominated, the friction coefficient becomes sensitive to the non-perturbative magnetic mass scale $m_{g}^{-1} \sim (αT)^{-1}$ which in turn leads to the friction coefficient's overall linear proportionality to $α$, which is much less suppressed in $α$ powers compared to the well understood term from Chern-Simons (CS) diffusion $(\propto α^5)$. On the other hand, this contribution to the friction coefficient is suppressed due to slow roll. We show that this can be viewed as a suppression of local spontaneous CPT violation for derivative couplings in general and that time correlations of nonlocal variables which do not fall off at large time separations are what allow an unsuppressed friction coefficient.