# Precision cosmology with redshift-space bispectrum: a perturbation theory based model at one-loop order

## TL;DR

This paper develops a perturbation theory-based model for the redshift-space matter bispectrum that accurately captures non-perturbative damping effects, improving cosmological parameter constraints from large-scale structure data.

## Contribution

It extends previous models by incorporating a univariate damping function at one-loop order, validated against N-body simulations for better accuracy in bispectrum predictions.

## Key findings

- Model matches N-body simulations for monopole and quadrupole moments
- Univariate damping function effectively controls non-perturbative effects
- Next-to-leading order calculations yield consistent damping parameters

## Abstract

The large-scale matter distribution in the late-time Universe exhibits gravity-induced non-Gaussianity, and the bispectrum, three-point cumulant is expected to contain significant cosmological information. In particular, the measurement of the bispectrum helps to tighten the constraints on dark energy and modified gravity through the redshift-space distortions (RSD). In this paper, extending the work by Taruya, Nishimichi & Saito (2010, Phys.Rev.D 82, 063522), we present a perturbation theory (PT) based model of redshift-space matter bispectrum that can keep the non-perturbative damping effect under control. Characterizing this non-perturbative damping by a univariate function with single free parameter, the PT model of the redshift-space bispectrum is tested against a large set of cosmological $N$-body simulations, finding that the predicted monopole and quadrupole moments are in a good agreement with simulations at the scales of baryon acoustic oscillations (well beyond the range of agreement of standard PT). The validity of the univariate ansatz of the damping effect is also examined, and with the PT calculation at next-to-leading order, the fitted values of the free parameter is shown to consistently match those obtained from the PT model of power spectrum by Taruya, Nishimichi & Saito (2010).