Nonthermal phase transitions after inflation

At the first stage of reheating after inflation, parametric resonance may rapidly transfer most of the energy of an inflaton field phi to the energy of other bosons. We show that quantum fluctuations of scalar and vector fields produced at this stage ar much greater than they would be in a state of thermal equilibrium. This leads to cosmological phase transitions of a new type, which may result in a copious production of topological defects and in a secondary stage of inflation after reheating.