Informal Pizza Seminar

(Pre-)Thermalization after Inflation

Juergen Berges

Heidelberg University

Explosive particle production at the end of the inflationary universe involves dynamics far away from the ground state or thermal equilibrium. The subsequent process of thermalization is crucial to provide the link to the successful Hot-Big-Bang cosmology. Standard approaches based on classical field theory approximations cannot provide this link and we show how to describe these phenomena in quantum field theory from first principles. The progress is based on efficient functional integral techniques, so-called n-particle irreducible effective actions, for which powerful nonperturbative approximation schemes are available.