Mohammad Ansari

Department of Physics, Sharif University of Technology 

Cosmic web: excursion set of saddle points and nearest neighbor statistics

Supervisor: Shant Baghram 

Abstract: When we observe the universe on large scale, we see interwoven web, called the cosmic web. The cosmic web has different components and a lot of information is in it. In both cases, considering the cosmic web’s components as the environment of structure formation or considering them as structures, studying the cosmic web has advantages. But because of the non-linear nature of the cosmic web, extracting information from it has some challenges. The main challenge is that there are several ways of quantifying the cosmic web, in which there is no agreement between them. In this work, by introducing the excursion set of saddle points, we try to find a way for modelling cosmic filaments. By this model, which is an extension of the excursion of peaks, we calculate the critical density contrast of filaments with the help of the ellipsoidal collapse model and then we calculate the statistics of filaments with the help of up crossing approximation. The statistics and mass-to-length relation of filaments will help us to judge between different cosmic web finders. Finally, we calculate the number density of filaments concerning filament mass and length with this model. In the following of this work, we examine another approach to extracting information from the cosmic web. We calculate the spherical contact and nearest neighbor quantities for cosmological simulations and catalogs of galaxy groups. We report the behavior of these quantities for distance. Also by calculating the statistical modes of quantities, we show a linear relationship between the mean and variance of spherical contact distribution.

یکشنبه 27 شهریور 1401، ساعت 15:00

Sunday 18 September 2022 – 15:00 Tehran Time

تالار جناب  – آمفی تئاتر دانشکده فیزیک