Florent Leclercq, Jens Jasche, Héctor Gil-Marín, Benjamin Wandelt
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 propose two methods designed to improve the correspondence between LPT and full numerical simulation of gravitational large-scale structure formation, in the mildly non-linear regime. We develop a computationally fast and flexible tool for a variety of cosmological applications. Our methods are 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 a relevant quantity (the Eulerian density contrast of the Lagrangian divergence of the displacement field) by one which 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 as predicted by LPT. We quantify the approximation error and the induced biases in the power spectrum and in the bispectrum as a function of scale and redshift. Our remapping procedures improves one-, two- and three-point statistics at scales smaller than 60 Mpc/h.
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http://arxiv.org/abs/1305.4642
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