Non-Gaussianity of one-point distribution functions in extended Lagrangian perturbation theory

概要

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We study the one-point probability distribution functions (PDFs) of thepeculiar velocity and the density fluctuation in a cosmological fluid. Within theperturbative approach to the structure formation scenario, the effect of "pressure" hasrecently been an area of research interest. The velocity dispersion of the cosmologicalfluid creates effective "pressure" or viscosity terms. From this viewpoint, because thepressure reflects a nonlinear effect of the motion of the fluid, the pressure model wouldinclude nonlinear effects. Here we analyze the Lagrangian linear perturbation PDFsfor both the Zel'dovich approximation and the pressure model. We find that the PDFsof the peculiar velocity remain Gaussian, even if we consider the pressure. For thePDFs 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.