Thermalisation after inflation

Abstract

During (re)heating of the universe after inflation, the relativistic decay products of the inflaton field $\varphi$ must lose energy and additional particles must be produced to attain a thermalised state at a temperature $T_{\text{reh}}$. We estimate the rate of energy loss via elastic and inelastic scattering interactions. Elastic scattering is an inefficient energy loss mechanism so inelastic processes, although higher order in the coupling $\alpha$, can be faster because more energy is transfered. The timescale to produce a particle number density of $\mathcal{O}(T_{\text{reh}}^3)$ is the inelastic energy loss timescale, $\sim ({\alpha }^3{n}_{\varphi }/T_{\text{reh}}^2{)}^{-1}$.

Comments: minor changes: another reference, additional sentences in introduction. Version accepted by journal