One-Loop Galaxy Bispectrum: Consistent Theory, Efficient Analysis with COBRA, and Implications for Cosmological Parameters

TL;DR

This paper introduces an efficient pipeline for analyzing the one-loop galaxy bispectrum in EFT, significantly improving computational speed and accuracy, and demonstrating its potential to enhance cosmological parameter constraints from large-scale structure data.

Contribution

The paper develops a novel, fast computational method using COBRA for one-loop EFT bispectrum analysis, including the first comprehensive treatment of stochastic EFT contributions.

Findings

Excellent match to data up to $k_{max}=0.15~h$ Mpc$^{-1}$.

Tighter cosmological constraints than tree-level bispectrum.

Potential for improved analysis of upcoming galaxy survey data.

Abstract

We present an efficient and accurate pipeline for the analysis of the redshift-space galaxy bispectrum multipoles at one-loop order in effective field theory (EFT). We provide a systematic theory derivation based on power counting, which features the first comprehensive treatment of stochastic EFT contributions -- these are found to significantly improve the match to data. Our computational pipeline utilizes the COBRA technique that expands the linear matter power spectrum over a basis of principal components based on a singular value decomposition, allowing the cosmology dependence to be captured to sub-permille accuracy with just eight templates. This transforms the problem of computing the one-loop EFT bispectrum to a simple tensor multiplication, reducing the computation time to around a second per cosmology with negligible loss of accuracy. Using these tools, we study the cosmological information in the bispectrum by analyzing PTChallenge simulations, whose gigantic volume provides the most powerful test of the one-loop EFT bispectrum so far. We find that the one-loop prediction provides an excellent match to the bispectrum data up to $k_{\rm max}=0.15~h$ Mpc$^{-1}$, as evidenced by the precise recovery of the dark matter density $\omega_\text{cdm}$, Hubble constant $H_0$, and mass fluctuation amplitude $\sigma_8$ parameters, and the amplitude of equilateral primordial non-Gaussianity (PNG) $f_{\rm NL}^{\rm equil}$. Combined with the power spectrum, the COBRA-based one-loop bispectrum multipoles yield tighter constraints than the tree-level bispectrum monopole, with the posteriors on $\omega_{\text{cdm}}$, $H_0$, and $\sigma_8$ shrinking by 41\%, 25\%, and 19\%, respectively. This suggests that the COBRA-based bispectrum analysis will be an important tool in the interpretation of data from ongoing redshift surveys such as DESI and Euclid.