Thermal field theory is applied to particle production rates in inflationary models, leading to new results for catalyzed or two-stage decay, where massive fields act as decay channels for the production of light fields. A numerical investigation of the Boltzmann equation in an expanding universe shows that the particle distributions produced during small amplitude inflaton oscillations or even alongside slowly moving inflaton fields can thermalize.

• Received 27 October 2008

DOI:https://doi.org/10.1103/PhysRevD.78.123526