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| Author(s): |
Leandro José Beraldo e Silva
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Física (IF/SBI) |
| Defense date: | 2015-02-05 |
| Examining board members: |
Laerte Sodre Junior;
Eduardo Serra Cypriano;
Gastao Cesar Bierrenbach Lima Neto;
José Ademir Sales de Lima;
Edivaldo Moura Santos
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| Advisor: | Laerte Sodre Junior; Marcos Vinicius Borges Teixeira Lima |
| Abstract | |
This thesis aims to study the dynamic and statistical aspects of dark matter in spherical distributions. The fact that their constituent particles interact gravitationally but not electromagnetically, and therefore its evolution is governed by long-range interactions, brings some theoretical complications in their description in terms of the statistical mechanics, difficulties shared with self-gravitating systems in general. To better understand these properties, we studied the distributions of dark matter in three different approaches. First, we used observational data, using gravitational lensing in galaxy clusters to compare the performance of some proposed models for the dark matter density profile. We divide these models in phenomenological or theoretical. All of the formers are able to describe the observational data with comparable performance. Among the theoretical models studied, the model called DARKexp describes the data as well as the formers. In a second approach, we use numerical simulation data to test a proposed function for the velocity distribution. This function includes the velocity anisotropy into the so called q-Gaussian distribution. We compared the performance of this function with the Gaussian function and concluded that the first is a better description of the data, even taking into account the introduction of an extra parameter, although still presenting some discrepancies, especially in the inner regions of the halo. Finally, we discuss the relevance of the concept of indistinguishability in determining the states of equilibrium of self-gravitating systems in general, suggesting an association of this concept with the mixing level of the system. We implement this association in a combinatorial analysis and study the consequences for the determination of the distribution function and the density profile. This association also raises some questions about the validity of the Vlasov equation during the process of violent relaxation. (AU) | |
| FAPESP's process: | 11/13237-3 - Determining properties of dark matter halos from Einstein rings data |
| Grantee: | Leandro José Beraldo e Silva |
| Support Opportunities: | Scholarships in Brazil - Doctorate |