Signatures of Non-Gaussianity in the Curvaton Model

TL;DR

This paper explores how non-Gaussian signals in the curvaton model, especially in the trispectrum via g_NL, can reveal non-quadratic features of the potential, with potential observability in future experiments.

Contribution

It demonstrates that the trispectrum's g_NL parameter is a key indicator of non-quadratic curvaton potentials, especially when the bispectrum's f_NL is small.

Findings

g_NL can be very large, up to 10^5

Non-Gaussianity may be more detectable in the trispectrum than the bispectrum

g_NL directly measures deviations from quadratic potential

Abstract

We discuss the signatures of non-Gaussianity in the curvaton model where the potential includes also a non-quadratic term. In such a case the non-linearity parameter f_NL can become very small, and we show that non-Gaussianity is then encoded in the non-reducible non-linearity parameter g_NL of the trispectrum, which can be very large. Thus the place to look for the non-Gaussianity in the curvaton model may be the trispectrum rather than the bispectrum. We also show that g_NL measures directly the deviation of the curvaton potential from the purely quadratic form. While g_NL depends on the strength of the non-quadratic terms relative to the quadratic one, we find that for reasonable cases roughly g_NL\sim O(-10^4)-O(-10^5), which are values that may well be accessible by future observations.