Baryon number non-conservation and phase transitions at preheating

There are well-known reasons to believe that inflation took place and was followed by reheating to some temperature T R . Before a thermal equilibrium was reached, the coherent oscillations of the inflaton could create the environment in which a resonant non-thermal production of particles could rapidly transfer energy from the inflaton to the other fields. This stage, known as preheating [1], has been a subject of intense studies. In particular, it was argued that both non-thermal phase transitions [2] and the generation of baryon asymmetry [3–5] could occur during preheating. We will describe two new field-theoretical phenomena that can be caused by coherent oscillations of the inflaton. One is a new example of a phase transition driven by the coherent oscillations of the inflaton. This transition has an unusual feature that it can start in a lower-energy ground state and end in a higher-energy metastable vacuum. We discuss this in Section II. In Section III we describe resonant generation of a fermion density through anomalous gauge interactions that can be the basis for baryogenesis. In contrast with the earlier work, where the analyses were based on analogies with thermal sphalerons [5,6] or topological defects [4], we construct an explicit solution that can be though of as a condensate of sphalerons. We show that the evolution of this solution can lead to a resonant growth of Chern-Simons number density.