Cosmological Nonlinear Structure Formation by Excursion Set Theory of<br/>Peaks

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Cosmological Nonlinear Structure Formation by Excursion Set Theory of
Peaks

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Type of Document: M.Sc. Thesis
Language: Farsi
Document No: 52124 (04)
University: Sharif University of Technology
Department: Physics
Advisor(s): Baghram, Shant
Abstract:
The statistics of Dark matter halos and their relation to luminous matter is one of the most important observational and theoretical tools in putting constraint on Cosmological models.There are two approaches for studying the statistics of dark matter halos in the context of non-linear structure formation: Excursion set theory (density contrast- variance space), and Peak theory (density contrast- position space). The goal of this thesis is studying the combination of these two approaches, which is known as Excursion Set of Peaks. We also address the ”cloud in cloud” problem, proposing an approximation for up-crossing problem. Then,we will address the bias parameter for matter-halo in the context of Excursion Set of Peaks. Finally, in order to classifying collapsed objects in the cosmic web we will study cosmological filaments in the context of ellipsoidal collapse which makes partially same predictions as the results of simulations. We find that the nonlinear density of filaments in the epoch of formation is almost mass independent and is in order of 30. We also study their statistics as a generalization to Excursion set of Peaks, which we name ”Excursion set of Saddle points
Keywords:
Cosmology ; Nonlinear Structure Formation ; Peak Excursion Set