Primordial Trispectrum from Entropy Perturbations in Multifield DBI Model

TL;DR

This paper analyzes the primordial trispectra in multifield DBI inflation, focusing on entropic mode interactions and their observational signatures in different momentum configurations.

Contribution

It provides the first detailed calculation of the four-point correlation functions in multifield DBI models, highlighting the role of entropic modes in sourcing curvature perturbations.

Findings

Distinct shape diagrams for equilateral and specialized configurations.

Entropic modes significantly influence the trispectrum in multifield models.

The shape differences can help distinguish multifield from single field inflation.

Abstract

We investigate the primordial trispectra of the general multifield DBI inflationary model. In contrast with the single field model, the entropic modes can source the curvature perturbations on the super horizon scales, so we calculate the contributions from the interaction of four entropic modes mediating one adiabatic mode to the trispectra, at the large transfer limit ($T_{RS}\gg1$). We obtained the general form of the 4-point correlation functions, plotted the shape diagrams in two specific momenta configurations, "equilateral configuration" and "specialized configuration". Our figures showed that we can easily distinguish the two different momenta configurations.