Primordial fluctuations from nonlinear couplings

TL;DR

This paper investigates how nonlinear couplings during inflation influence the primordial fluctuation spectrum, revealing scale invariance with logarithmic corrections and exploring the quantum versus classical nature of these fluctuations.

Contribution

It provides a detailed analysis of the effects of nonlinear couplings on the primordial fluctuation spectrum, including infrared divergence impacts and spectral tilting.

Findings

Conformally invariant theories predict a scale-invariant spectrum.

Infrared divergences introduce logarithmic corrections, tilting the spectrum blue.

Discussion on the quantum versus classical nature of fluctuations.

Abstract

We study the spectrum of primordial fluctuations in theories where the inflaton field is coupled to massless fields and/or to itself. Conformally invariant theories generically predict a scale invariant spectrum. Scales entering the theory through infrared divergences cause logarithmic corrections to the spectrum, tiltilng it towards the blue. We discuss in some detail whether these fluctuations are quantum or classical in nature.