We present a new approach to computing the matter density power spectrum, from large linear scales to small highly nonlinear scales. Instead of explicitly computing a partial series of high-order diagrams, as in perturbative resummation schemes, we embed the standard perturbation theory within a realistic nonlinear Lagrangian-space ansatz. We also point out that an "adhesion-like" regularization of the shell-crossing regime is more realistic than a "Zel'dovich-like" behavior, where particles freely escape to infinity. This provides a "cosmic web" power spectrum with good small-scale properties that provide a good matching with a halo model on mildly nonlinear scales. We obtain a good agreement with numerical simulations on large scales, better than 3% for $k\leq 1 h$Mpc$^{-1}$, and on small scales, better than 10% for $k \leq 10 h$Mpc$^{-1}$, at $z \geq 0.35$, which improves over previous methods.
In modern cosmology, the precision of the theoretical prediction is increasingly required. In cosmological $N$-body simulations, the effect of higher-order Lagrangian perturbation on the initial conditions appears in terms of statistical quantities of matter density field. We have considered the effect of third-order Lagrangian perturbation (3LPT) on the initial conditions, which can be applied to Gadget-2 code. Then, as statistical quantities, non-Gaussianity of matter density field has been compared between cases of different order perturbations for the initial conditions. Then, we demonstra…
We present the one-loop 2-point function of biased tracers in redshift space computed with Lagrangian perturbation theory, including a full resummation of both long-wavelength (infrared) displacements and associated velocities. The resulting model accurately predicts the power spectrum and correlation function of halos and mock galaxies from two different sets of N-body simulations at the percent level for quasi-linear scales, including the damping of the baryon acoustic oscillation signal due to the bulk motions of galaxies. We compare this full resummation with other, approximate, techniques…
Lagrangian algorithms to simulate the evolution of cold dark matter (CDM) are invaluable tools to generate large suites of mock halo catalogues. In this paper, we first show that the main limitation of current semi-analytical schemes to simulate the displacement of CDM is their inability to model the evolution of overdensities in the initial density field, a limit that can be circumvented by detecting halo particles in the initial conditions. We thus propose `MUltiscale Spherical Collapse Lagrangian Evolution Using Press-Schechter' (muscle-ups), a new scheme that reproduces the results from La…
Post-collapse Lagrangian perturbation theory in three dimensions
Institute for Advanced Research, Nagoya University(名古屋大学高等研究院);Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University(名古屋大学小林-益川粒子宇宙起源研究所);Sorbonne Université, CNRS, UMR7095, Institut d’Astrophysique de Paris(索邦大学,法国国家科学研究中心,联合研究实验室7095,巴黎天体物理研究所);Center for Gravitational Physics and Quantum Information, Yukawa Institute for Theoretical Physics, Kyoto University(京都大学汤川理论物理研究所引力物理与量子信息中心);Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai institute for Advanced Study, University of Tokyo(东京大学前沿研究机构,卡弗里宇宙物理学与数学研究所(WPI));Korea Institute for Advanced Study(韩国高等科学研究院);Division of Theoretical Physics, Ruđer Bošković Institute(鲁德·博什科维奇研究所理论物理部);Department of Astrophysics, University of Vienna(维也纳大学天体物理学系);Faculty of Mathematics, University of Vienna(维也纳大学数学学院)
We develop a Lagrangian Perturbation Theory (LPT) framework to study the clustering of cold dark matter (CDM) in cosmologies with massive neutrinos. We follow the trajectories of CDM particles with Lagrangian displacements fields up to third order in perturbation theory. Once the neutrinos become non-relativistic, their density fluctuations are modeled as being proportional to the CDM density fluctuations, with a scale-dependent proportionality factor. This yields a gravitational back-reaction that introduces additional scales to the linear growth function, which is accounted for in the higher…