Non-Gaussianity beyond slow roll in multi-field inflation

TL;DR

This paper derives an exact expression for the bispectrum parameter in multi-field inflation beyond slow-roll, introduces a new inflationary model with observable non-Gaussianity, and highlights the significance of the trispectrum as a potential dominant signal.

Contribution

It provides an exact formula for non-Gaussianity in multi-field inflation beyond slow-roll and explores a new model where non-Gaussian signals are observable at the end of inflation.

Findings

Bispectrum can grow to observable levels in certain models.

Trispectrum may be the dominant non-Gaussian signal.

Exact expression for f_NL beyond slow-roll regime.

Abstract

We study the non-Gaussianity generated during multiple-field inflation. We provide an exact expression for the bispectrum parameter f_NL which is valid beyond the slow-roll regime, valid for certain classes of inflationary models. We then study a new, exact multi-field inflationary model considering a case where the bispectrum grows to observable values at the end of inflation. We show that in this case the trispectrum is also large and may even provide the dominant signal of non-Gaussianity.