On resumming inflationary perturbations beyond one-loop

Abstract

It is well known that the correlation functions of a scalar field in a quasi-de Sitter space exhibit at the loop level cumulative infrared effects proportional to the total number of e-foldings of inflation. Using the in-in formalism, we explore the behavior of these infrared effects in the large N limit of an O(N)-invariant scalar field theory with quartic self-interactions. By resumming all higher-order loop diagrams non-perturbatively, we show that the connected four-point correlation function, which is a signal of non-Gaussianity, is non-perturbatively enhanced with respect to its tree-level value. © IOP Publishing Ltd.