Seminar 1: Nonlinear structure formation and haloes statistic in FDM model
Melika Sarrami
Department of Physics, Sharif University of Technology
Seminar 2: Axion as Dark Matter
Mohammad-Reza Ebrahimi
Department of Physics, Sharif University of Technology
Seminar 3: Nonlocal gravity and its local limit in cosmology
Javad Tabatabaei
Department of Physics, Sharif University of Technology
Seminar 4: Statistical Methods On Large Scale Structure
Mohammad Hossein Amiri
Department of Physics, Sharif University of Technology
یکشنبه 13 شهریور 1401، ساعت 19:00
Sunday 4 September 2022 – 19:00 Tehran Time
اتاق سمینار مجازی –Virtual Seminar Room
https://vc.sharif.edu/ch/cosmology
گزینه ورود به صورت مهمان – Enter as a Guest
Abstract 1: ΛCDM has successfully explained the universe’s large-scale structure, the statistics of the cosmic microwave background, and cluster abundances. However, recent observations have pointed out drawbacks of ΛCDM at small-scale. Fuzzy dark matter(FDM) is an alternative theory designed to solve small-scale problems. We derive the halo mass function for FDM by solving the excursion set problem with a mass-dependent barrier function; then, we are going to compare the approach and results of the ΛCDM model and halos statistic that stem from it with FDM model. In the following, we find out the discrepancy between these two models that comprise transfer function, power spectrum, bias, and number density. Finally, we realize that if the dark matter is a mixture of cold dark matter (CDM) and FDM, there will be a suppression on the halo substructure on small scales, which may be able to solve the missing satellite problem faced by the pure CDM model.
Abstract 2: Despite significant discoveries in cosmology, we still don’t know what Dark Matter is. Dark Matter candidates, for example, have a very broad mass spectrum, ranging from extremely tiny masses of around $10^{-22}\mathrm{eV}$ to very massive masses on the scale of Primordial Black Holes ($10^{30}\mathrm{eV}$). In particular, the subject of this seminar is those dark matter candidates that have a very low mass (of order $10^{-22}\mathrm{eV}$). Because of their extremely low mass, these dark matter particles exhibit wave behavior in their dynamics, which has interesting implications on structure formation. In this seminar, we will look at the wave dynamics of these particles and its impacts on structure formation.
Abstract 3: The theory of nonlocal gravity is a classical modification of Einstein’s general relativity that explores nonlocal effects of gravity by putting aside the locality postulate. In this talk we introduce the local limit of this theory, or in other words, we consider nonlocality with only a short-term memory. We show that the corrections of this theory to the equations governing the dynamics of the homogenous universe and its perturbations are determined only by an unknown function of time which acts like the dielectric permittivity in electrodynamics. Using the numerical evaluation of this function, to explain some recent observational tensions in cosmology, is the goal of this research.
Abstract 4: In the process of exploring the universe on the large scale, one of the most important questions is how to predict the behavior and motion of matter within the impact of gravity. Unfortunately, today we can’t simulate the whole universe through the lack of computing power. So because of the high order number of dark matter halos, we turn to statistics to help us understand the large scale behavior. Using some statistical methods and statistical parameters (like nearest neighbor distribution & …) on large scale structure we can extract good information from galaxy halos and cosmic web.
