Matter bispectrum of large-scale structure with Gaussian and non-Gaussian initial conditions: Halo models, perturbation theory, and a three-shape model

Abstract

We study the matter bispectrum of large-scale structure by comparing the predictions of different perturbative and phenomenological models with the full three-dimensional bispectrum from $N$-body simulations estimated using modal methods. We show that among the perturbative approaches, effective field theory succeeds in extending the range of validity furthest on intermediate scales, at the cost of free additional parameters. By studying the halo model, we show that although it is satisfactory in the deeply non-linear regime, it predicts a deficit of power on intermediate scales, worsening at redshifts $z>0$. By comparison with the $N$-body bispectrum on those scales, we show that there is a significant squeezed component underestimated in the halo model. On the basis of these results, we propose a new three-shape model, based on the tree-level, squeezed and constant bispectrum shapes we identified in the halo model; after calibration this fits the simulations on all scales and redshifts of interest. We extend this model further to primordial non-Gaussianity of the local and equilateral types by showing that the same shapes can be used to describe the additional non-Gaussian component in the matter bispectrum. This method provides a HALOFIT-like prototype of the bispectrum that could be used to describe and test parameter dependencies and should be relevant for the bispectrum of weak gravitational lensing and wider applications.

8 pages, 7 figures; significant new results added and title modified; version published in Phys. Rev. D

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• The Power of Locality: Primordial Non-Gaussianity at the Map Level
• Quijote-PNG: Quasi-maximum likelihood estimation of Primordial Non-Gaussianity in the non-linear dark matter density field
• Cosmological constraints from the power spectrum and bispectrum of 21cm intensity maps
• Probing primordial non-Gaussianity with the power spectrum and bispectrum of future 21cm intensity maps
• The two and three-loop matter bispectrum in perturbation theories
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• Towards cosmological constraints from the compressed modal bispectrum: a robust comparison of real-space bispectrum estimators
• Biases to primordial non-Gaussianity measurements from CMB secondary anisotropies
• Quijote-PNG: Quasi-maximum likelihood estimation of Primordial Non-Gaussianity in the non-linear halo density field
• Squeezing information from radio surveys to probe the primordial Universe