On Resumming Inflationary Perturbations beyond One-loop

TL;DR

This paper investigates the non-perturbative infrared effects in inflationary scalar perturbations, demonstrating that resumming higher-order loops significantly enhances non-Gaussianity signals in the large N limit.

Contribution

It introduces a non-perturbative resummation approach for infrared effects in inflationary correlators within an O(N) scalar field theory.

Findings

Connected four-point function is non-perturbatively enhanced.

Infra-red effects grow with the number of e-foldings.

Resummation alters the expected level of non-Gaussianity.

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 infra-red effects proportional to the total number of e-foldings of inflation. Using the in-in formalism, we explore the behavior of these infra-red 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.