The Trispectrum in the Multi-brid Inflation

TL;DR

This paper analyzes the trispectrum in multi-brid inflation models, revealing that $ au_{NL}$ is always positive and approximately related to $f_{NL}$, while $g_{NL}$ can vary in sign and magnitude, highlighting key non-Gaussian features.

Contribution

It provides a detailed characterization of the trispectrum parameters $ au_{NL}$ and $g_{NL}$ in multi-brid inflation, especially the two-brid model, which was not previously fully explored.

Findings

$ au_{NL}$ is always positive and roughly equals $(6/5 f_{NL})^2$ in low-scale inflation.

$g_{NL}$ can be negative or positive, with magnitude comparable to or larger than $ au_{NL}$.

The sign and magnitude of $g_{NL}$ vary significantly, indicating diverse non-Gaussian signatures.

Abstract

The trispectrum is at least as important as the bispectrum and its size can be characterized by two parameters $\tau_{NL}$ and $g_{NL}$. In this short paper, we focus on the Multi-brid inflation, in particular the two-brid inflation model in arXiv.0805.0974, and find that $\tau_{NL}$ is always positive and roughly equals to $({6\over 5}f_{NL})^2$ for the low scale inflation, but $g_{NL}$ can be negative or positive and its order of magnitude can be the same as that of $\tau_{NL}$ or even larger