Adiabaticity and the Fate of Non-Gaussianities: The Trispectrum and Beyond

TL;DR

This paper investigates how non-Gaussianities, specifically the trispectrum, evolve during inflation and finds they tend to diminish if the fluctuations become adiabatic, extending previous analyses beyond the bispectrum.

Contribution

It extends the analysis of non-Gaussianities beyond the bispectrum to the trispectrum and higher correlations in two-field inflation models, showing their exponential suppression during adiabatic evolution.

Findings

Local trispectrum parameters tau_NL and g_NL are exponentially suppressed during adiabatic evolution.

The suppression mechanism applies similarly to higher point correlations.

The results are derived within a class of two-field inflation models using the delta N formalism.

Abstract

Extending the analysis of [1011.4934] beyond the bispectrum, we explore the superhorizon generation of local non-gaussianities and their subsequent approach to adiabaticity. Working with a class of two field models of inflation with potentials amenable to treatment with the delta N formalism we find that, as is the case for f_{NL}^{local}, the local trispectrum parameters tau_{NL} and g_{NL} are exponentially driven toward values which are slow roll suppressed if the fluctuations are driven into an adiabatic mode by a phase of effectively single field inflation. We argue that general considerations should ensure that a similar behavior will hold for the local forms of higher point correlations as well.