Nonequilibrium quantum field theory in cosmology

Abstract

Nonequilibrium quantum field theory has recently become an important tool in research in particle physics and cosmology. The salient feature of nonequilibrium quantum field theory is its formalism which treats the propagators as independent variables. In this thesis, the formulation of nonequilibrium quantum field theory, consisting of the closed-time path integral and the 2-particle-irreducible formalism, is reviewed. The methods are then applied to the study of inflaton dynamics in curved spacetime, with and without fermion coupling, and the dynamical equations for the inflaton mean field and propagators are derived. It is found that these equations respect causality and have the potential of predicting the inflaton damping and the fermion production, even though their solution cannot be obtained analytically.