On the Effective Evolution for the Inflaton∗

Despite the many studies on the dynamics of inflation, much still remains to be done in the context of understanding several aspects concerning the microscopic dynamics underlying many of the models for inflation, particularly in those cases where the inflaton is coupled to several other fields, like in hybrid inflation models and supersymmetric (SUSY) model extensions. In most of these models it is a fact that large regions of parameter space still remain unexplored and that can be feasible to inflation and new phenomena. This is also true when we consider the common approximations used to study the different aspects of inflation, which most of the time have been restricted to particular perturbative and linear regimes. This is understandable since when nonperturbative and nonlinear effects may become important standard techniques may not always apply, which have slowed down progress in that direction. At the same time methods and techniques developed in quantum field theory devoted to the description of nonequilibrium dynamics have become essential to study these new phenomena, like in those cases where there can be non-negligible particle and radiation production, e.g. in the description of the preheating phase after isentropic inflation or the study of the emergence of non-isentropic inflation (or warm inflation) scenarios, where the scalar inflaton field dissipates non-negligible amounts of radiation during inflation 1,2,3,4. Of special interest as concerned to non-isentropic inflationary scenarios is the process of how the inflaton can dissipate its energy during inflation.