Primordial non-Gaussianity in noncanonical warm inflation with nonminimal derivative coupling

TL;DR

This work analyzes primordial non-Gaussianity in NMDC noncanonical warm inflation, decomposing the total $f_{NL}$ into a δN part and an intrinsic part. The δN contribution is slow-roll suppressed and largely scale-independent, while the intrinsic part, driven by thermal fluctuations and the nonminimal derivative coupling, dominates and depends on the sound speed $c_s$, the NMDC parameters $F$ and $Z$, and the dissipation strength $Q$, yielding an equilateral-shaped signal. The total $f_{NL}$ is well described by $f_{NL}^{total} \approx -\frac{5}{3} \ln\sqrt{3(1+Q)} [\frac{L_X}{L_X+3F}(c_s^{-2}-1) + 2Z\frac{L_X c_s^{-2}+9F}{L_X+3F}]$, with Planck bounds constraining $c_s$ and $F$; in the limit $F\to0$ the results reduce to GR-based noncanonical warm inflation. The study highlights a novel hybrid non-Gaussian signature arising from the interplay of NMDC, noncanonical kinetics, and thermal dissipation, and outlines future numerical constraints on specific models.

Abstract

This paper presents and investigates non-Gaussian perturbations for the warm k-inflation model that is driven by pure kinetic energy. The two complementary components of the overall non-Gaussianity are the three-point and four-point correlations. The intrinsic non-Gaussian component, denoted as the nonlinear parameter f_{NL}^{int}, is rooted in the three-point correlation for the inflaton field. Meanwhile, the δN part non-Gaussianity, denoted as f_{NL}^{δN}, is the contribution attributed to the four-point correlation function of the inflaton field. In this paper, the above two components in warm k-inflation are individually computed and analyzed. Then, comparisons and discussions between them are conducted, and the non-Gaussian theoretical results are compared with experimental observations to determine the range of model parameters within the allowable range of observation.