One-point remapping of Lagrangian perturbation theory in the mildly non-linear regime of cosmic structure formation

TL;DR

This paper introduces a remapping method for Lagrangian perturbation theory that enhances the accuracy of cosmic web feature predictions in the mildly non-linear regime, improving statistical measures down to 8 Mpc/h.

Contribution

The authors develop a fast, flexible remapping technique that aligns LPT density fields more closely with full N-body simulations, improving higher-order statistics.

Findings

Improved the correspondence of LPT with N-body simulations in the mildly non-linear regime.

Enhanced the accuracy of power spectrum and bispectrum predictions.

Achieved better statistical agreement at scales down to 8 Mpc/h.

Abstract

On the smallest scales, three-dimensional large-scale structure surveys contain a wealth of cosmological information which cannot be trivially extracted due to the non-linear dynamical evolution of the density field. Lagrangian perturbation theory (LPT) is widely applied to the generation of mock halo catalogs and data analysis. In this work, we compare topological features of the cosmic web such as voids, sheets, filaments and clusters, in the density fields predicted by LPT and full numerical simulation of gravitational large-scale structure formation. We propose a method designed to improve the correspondence between these density fields, in the mildly non-linear regime. We develop a computationally fast and flexible tool for a variety of cosmological applications. Our method is based on a remapping of the approximately-evolved density field, using information extracted from N-body simulations. The remapping procedure consists of replacing the one-point distribution of the density contrast by one which better accounts for the full gravitational dynamics. As a result, we obtain a physically more pertinent density field on a point-by-point basis, while also improving higher-order statistics predicted by LPT. We quantify the approximation error in the power spectrum and in the bispectrum as a function of scale and redshift. Our remapping procedure improves one-, two- and three-point statistics at scales down to 8 Mpc/h.