2005/04/20 by Takayuki Tatekawa
Physics and Astronomy · #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #Statistical Mechanics and Entropy #astro-ph #gr-qc
paper · pdf · doi:10.1088/1475-7516/2005/04/018
published as JCAP 0504 (2005) 018 · 15 pages, 11 figures, accepted for publication in JCAP
arxiv created 2005/04/20 · openalex publication_date 2005/04/29 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/30
We study the one-point probability distribution functions (PDFs) of the peculiar velocity and the density fluctuation in a cosmological fluid. Within the perturbative approach to the structure formation scenario, the effect of 'pressure' has recently been an area of research interest. The velocity dispersion of the cosmological fluid creates effective 'pressure' or viscosity terms. From this viewpoint, because the pressure reflects a nonlinear effect of the motion of the fluid, the pressure model would include nonlinear effects. Here we analyse the Lagrangian linear perturbation PDFs for both the Zel'dovich approximation and the pressure model. We find that the PDFs of the peculiar velocity remain Gaussian, even if we consider the pressure. For the PDFs of the density fluctuation, the occurrence of non-Gaussianity depends on the 'equation of state' for the fluid. Therefore we distinguish the 'equation of state' using the PDFs.