Resummation of infrared logarithms in de Sitter space via Dyson-Schwinger equations: The ladder-rainbow approximation

摘要: We study the infrared (large separation) behavior of a massless minimally coupled scalar quantum field theory with quartic self interaction in de Sitter spacetime. show that perturbation series strength is singular and secular, i.e. it does not lead to uniform approximation solution region. Only nonperturbative resummation can capture correct behavior. seek justify this picture using Dyson-Schwinger equations ladder-rainbow approximation. are able write down an ordinary differential equation obeyed by two-point function perform its asymptotic analysis. Indeed, while perturbative series-truncated at any finite order-is growing infrared, full sum be decaying.