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The Study of Cosmological Structures Formation by Physics of Stochastic Processes

Ayromlou, Mohammad Reza | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49094 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Baghram, Shant; Rahimi Tabar, Mohammad Reza
  7. Abstract:
  8. 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 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 having smoothed density feld Excursion Set Theory uses a specifc window function(flter) called sharp k-space, which is a top-hat in Fourier space. If one use this specifc window function the process of density feld 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 using the concept of Markov processes to defne some mirror trajectories and that’s one of the basics of this theory; However practically, instead of using sharp k-space flter, physicists use more common flters 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 DarkSky simulation we investigate Einstein-Markov length of density contrast when it is smoothed with a top-hat flter. The results give us the best variance step which gives Markov process for smoothed density contrast with a top-hat window function
  9. Keywords:
  10. Cosmology ; Stochastic Process ; Structure Formation ; Universe Large-Scale Structure

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