Primordial non-Gaussianity in noncanonical warm inflation

TL;DR

This paper investigates the non-Gaussian features of primordial fluctuations generated by noncanonical warm inflation, deriving an analytic expression for the non-Gaussianity parameter and comparing it with standard models.

Contribution

It provides an analytic form for the non-Gaussianity parameter in noncanonical warm inflation and analyzes its magnitude and observational constraints, especially in DBI inflation.

Findings

Derived an explicit expression for $f_{NL}$ in noncanonical warm inflation.

Compared non-Gaussianity with standard and canonical warm inflation models.

Constrained sound speed using PLANCK data in the context of DBI inflation.

Abstract

We study the bispectrum of the primordial curvature perturbation on uniform-density hypersurfaces generated by a kind of the noncanonical warm inflation, wherein the inflation is provided by a noncanonical scalar inflaton field that is coupled to radiation through a thermal dissipation effect. We obtain an analytic form for the nonlinear parameter $f_{NL}$ that describes the non-Gaussianity in first-order cosmological perturbation theory and analyse the magnitude of this nonlinear parameter. We make a comparison between our result and those of the standard inflation and the canonical warm inflation. We also discuss when the contribution to the non-Gaussianity due to the second-order perturbation theory becomes more important and what effect can be observed. We take the Dirac-Born-Infeld (DBI) inflation as a concrete example to find how the sound speed and the thermal dissipation strength to decide the non-Gaussianity and to get a lower bound of the sound speed constrained by PLANCK.