Primordial non-Gaussianity in warm k-inflation with nonminimal derivative coupling
Abstract
This paper derives the finite-inertia intrinsic thermal bispectrum in potential-free warm k-inflation with nonminimal derivative coupling (NMDC). On a fixed Friedmann--Lema\^ıtre--Robertson--Walker geometry, the complete cubic inflaton action determines the nonlinear stochastic source, encompassing temporal, spatial-gradient, and field-dependent kinetic interactions. The retarded solution captures the full momentum-triangle dependence while retaining unequal-time correlations, whereas its equilateral limit yields the intrinsic nonlinearity parameter. The power spectrum is computed with the same response and Gaussian initial state, thereby fixing the statistical normalization. A complementary local freeze-out reduction makes the interaction coefficients and two geometric shape contributions explicit. Comparison along an evolving near-attractor trajectory indicates that unequal-time finite-inertia propagation is crucial for quantitatively predicting the intrinsic bispectrum. The analysis also derives the slow-roll-suppressed nonlinear δN conversion, together with the Arnowitt--Deser--Misner constraints and cubic vertices that characterize the direct gravitational effects of NMDC. These results clarify the respective roles of local freeze-out estimates and finite-inertia stochastic evolution in the nonlinear prediction.
Related
- Large primordial non-Gaussianity from transient turns in Higgs-R2 inflation
- Nonminimal Scalar-curvature Coupling Noncanonical Warm Inflation
- Nonminimal couplings and preheating effects in R2-Higgs inflation after ACT and SPT data
- Relic Neutrinos Probing Small Scale Primordial Non-Gaussianity
- Ultra-slow-roll Inflation with Non-perturbative Non-Gaussianity and Scalar Induced Gravitational Waves
BibTeX
@misc{zhang2026primordial,
title = {{Primordial non-Gaussianity in warm $k$-inflation with nonminimal derivative coupling}},
author = {Xiao-Min Zhang and Zi-Xin Bai and Qing-Ze Shi and Run-Qing Zhao and Peng-Cheng Chu and Yun-Cai Feng},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.07492},
eprint = {2611.07492},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.07492},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Primordial non-Gaussianity in warm k-inflation with nonminimal derivative coupling
AU - Xiao-Min Zhang
AU - Zi-Xin Bai
AU - Qing-Ze Shi
AU - Run-Qing Zhao
AU - Peng-Cheng Chu
AU - Yun-Cai Feng
PY - 2026
DA - 2026/11/05
PB - arXiv
DO - 10.48550/arxiv.2611.07492
UR - https://arxiv.org/abs/2611.07492
AB - This paper derives the finite-inertia intrinsic thermal bispectrum in potential-free warm k-inflation with nonminimal derivative coupling (NMDC). On a fixed Friedmann--Lema\^ıtre--Robertson--Walker geometry, the complete cubic inflaton action determines the nonlinear stochastic source, encompassing temporal, spatial-gradient, and field-dependent kinetic interactions. The retarded solution captures the full momentum-triangle dependence while retaining unequal-time correlations, whereas its equilateral limit yields the intrinsic nonlinearity parameter. The power spectrum is computed with the same response and Gaussian initial state, thereby fixing the statistical normalization. A complementary local freeze-out reduction makes the interaction coefficients and two geometric shape contributions explicit. Comparison along an evolving near-attractor trajectory indicates that unequal-time finite-inertia propagation is crucial for quantitatively predicting the intrinsic bispectrum. The analysis also derives the slow-roll-suppressed nonlinear δN conversion, together with the Arnowitt--Deser--Misner constraints and cubic vertices that characterize the direct gravitational effects of NMDC. These results clarify the respective roles of local freeze-out estimates and finite-inertia stochastic evolution in the nonlinear prediction.
ER -