Non-gaussianity of one-point distribution functions in the universe

We study the one-point probability distribution functions (PDFs) of the density fluc- Tuation in a cosmological fluid. Within the perturbative approach to the structure formation scenario, the effect of "pressure" in the fluid has recently been an area of research interest. Here we analyze the effect of "pressure" for Lagratigian linear perturbation PDFs. Then we consider the dependence of the dark energy modeis. According to recent observations, the existence of the dark energy has been consid- ered. Even though we have obtained the constraint of the equation of the State for the dark energy (p = wp) as -1 < w < -0.78 by combining WM AP data with other astronomical data, in order to pin down w, it is necessary to present other independent observational tools. For this purpose, we consider the ui dependence of the non-Gaussianity of the density distribution generated by the nonlinear dynamics. In order to subtract the non-Gaussianity, we follow the semi-Analytic approach based on the Lagrangian linear perturbation theory which provide accurate value for the quasi-nonlinear region.