A Diagrammatic Approach to Scalar Field Correlators during Inflation

TL;DR

This paper develops a diagrammatic method within the in-in formalism to analyze infrared divergences in scalar field correlators during inflation, revealing non-perturbative enhancements in non-Gaussian signals for large N theories.

Contribution

It introduces a diagrammatic approach to handle infrared divergences in inflationary scalar fields, specifically demonstrating non-perturbative effects in large N O(N) models.

Findings

Connected four-point function is non-perturbatively enhanced.

Infrared divergences are managed using a diagrammatic in-in formalism.

Non-Gaussianity signals are significantly affected in large N theories.

Abstract

We consider a self-interacting scalar field in a de Sitter background and deal with the associated infrared divergences in a purely diagrammatic way using the in-in formalism. In the particular case of a large N O(N) invariant scalar field theory with quartic self-interactions we recover the result 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.