Density fluctuations from warm inflation

Abstract

Thermal fluctuations provide the main source of large scale density perturbations in warminflationary models of the early universe. For the first time, general results are obtained for thepower spectrum in the case when the friction coefficient in the inflaton equation of motion dependson temperature. A large increase in the amplitude of perturbations occurs when the frictioncoefficient increases with temperature. This has to be takeninto account when constructing models of warm inflation. New results are also given for the thermalfluctuations in the weak regime of warm inflation when the friction coefficient is relatively small.