Enabling Polyspectra via Stochastic Realizations of Inverse Decay Curvature Perturbations in Axion Inflation
Abstract
Current and upcoming galaxy-redshift surveys offer a promising path for constraining inflationary physics. These constraints are often imposed by relating correlations of the primordial curvature perturbation to the late-time galaxy correlation functions. The primordial correlators can either be computed analytically, or via realizations of the primordial curvature perturbations that are initialized on a grid and evolved numerically according to the classical equations of motion. In this work we take a hybrid approach, initializing the fields in the Bunch-Davies vacuum; and then imposing time evolution through direct numerical integration. Our method efficiently generates realizations of the inverse decay primordial curvature perturbations for axion inflation---an inflationary model in which a pseudoscalar inflaton field couples to a U(1) gauge field via a Chern-Simons interaction. Depending on the choice of parameter ξ∈{2, 2.5, 3}, which controls gauge field particle production in this model, our method generates realizations with an average runtime of a few hours on 1 CPU core. We compute the power spectrum and bispectrum from these realizations and find a surprisingly large discrepancy between our result and previous work that used an approximation for the gauge field mode functions---up to a factor of ∼4 difference for the bispectrum in the case of ξ=2. This new method enables not only rapid computation of higher order polyspectra, but also generation of initial conditions for large-scale structure analyses.
Related
- Scalar perturbations in two-scalar-field warm inflation
- Thermal-acoustic fermionic dynamics and primordial perturbations in warm Yukawa inflation
- Audible curvaton: modulated phase transition as the origin of large-scale curvature perturbations and gravitational wave anisotropies
- How do late-time photons "record" primordial curvature perturbations?
- Primordial Black Holes from Vector-Induced Curvature Perturbations Sourced by Primordial Magnetic Fields
BibTeX
@misc{reinhard2026enabling,
title = {{Enabling Polyspectra via Stochastic Realizations of Inverse Decay Curvature Perturbations in Axion Inflation}},
author = {Matthew A. Reinhard and Zachary Slepian and Atsushi Taruya},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.18748},
eprint = {2610.18748},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.18748},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Enabling Polyspectra via Stochastic Realizations of Inverse Decay Curvature Perturbations in Axion Inflation
AU - Matthew A. Reinhard
AU - Zachary Slepian
AU - Atsushi Taruya
PY - 2026
DA - 2026/10/13
PB - arXiv
DO - 10.48550/arxiv.2610.18748
UR - https://arxiv.org/abs/2610.18748
AB - Current and upcoming galaxy-redshift surveys offer a promising path for constraining inflationary physics. These constraints are often imposed by relating correlations of the primordial curvature perturbation to the late-time galaxy correlation functions. The primordial correlators can either be computed analytically, or via realizations of the primordial curvature perturbations that are initialized on a grid and evolved numerically according to the classical equations of motion. In this work we take a hybrid approach, initializing the fields in the Bunch-Davies vacuum; and then imposing time evolution through direct numerical integration. Our method efficiently generates realizations of the inverse decay primordial curvature perturbations for axion inflation---an inflationary model in which a pseudoscalar inflaton field couples to a U(1) gauge field via a Chern-Simons interaction. Depending on the choice of parameter ξ∈{2, 2.5, 3}, which controls gauge field particle production in this model, our method generates realizations with an average runtime of a few hours on 1 CPU core. We compute the power spectrum and bispectrum from these realizations and find a surprisingly large discrepancy between our result and previous work that used an approximation for the gauge field mode functions---up to a factor of ∼4 difference for the bispectrum in the case of ξ=2. This new method enables not only rapid computation of higher order polyspectra, but also generation of initial conditions for large-scale structure analyses.
ER -