بررسی تشکیل ساختارهای کیهانی با استفاده از فیزیک فرایندهای تصادفی

The Study of Cosmological Structure Formation by Physics of Stochastic Processes

محمدرضا آیرملو (دانشکده فیزیک دانشگاه صنعتی شریف)

استاد راهنما: شانت باغرام و محمدرضارحیمی تبار

دفاع از رساله کارشناسی ارشد

به مکان و زمان جلسه توجه فرمایید

Abstract:  One of the most important studies in cosmology is the study of Large Scale Structure of cosmos, where one of the useful and valuable tools is the Excursion Set Theory( EST). EST or Extended Press-Schechter is a theory based on stochastic processes which gives us the distribution function (mass function) of dark matter halos. In order to have smoothed density field, Excursion Set Theory uses a specific window function (filter) called sharp k-space, which is a top-hat in Fourier space. If one uses this specific window function the process of density field with respect to variance will be a Markov process, with any other window function the process won’t be a Markov process.

Excursion Set Theory uses the concept of Markov processes to define some mirror trajectories and that’s one of the basics of the theory. However practically, instead of using sharp k-space filter, physicists use more common filters such as top-hat and Gaussian. In the other side there is an important concept in stochastic processes called Einstein-Markov length, which is a length of nature, where a stochastic process becomes Markovian. In this Thesis using Dark-Sky simulation we investigate Einstein-Markov length of density contrast when it is smoothed with a top-hat filter. The results give us the best variance step which gives Markov process for smoothed density contrast with a top-hat window function.

یکشنبه 4 مهر ماه 1395، ساعت 15:00

دانشکده فیزیک، آمفی تئاتر (تالارجناب)