Scalar field quantum fluctuations and fine-tuning in chaotic inflationary models

During chaotic inflation, the dispersion of a scalar field can show interesting nonlinear effects. This is not seen in treatments which combine a deterministic description for the mean-field evolution with a diffusion approximation for the quantum fluctuations. We derive a criterion which distinguishes the diffusive regime from the nonlinear regime using stochastic dynamics in models of noninteracting multiple scalar fileds. In the nonlinear …