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Dynamics and statistical mechanics of dark matter halos

Grant number: 14/23751-4
Support type:Scholarships in Brazil - Post-Doctorate
Effective date (Start): September 01, 2015
Effective date (End): September 05, 2018
Field of knowledge:Physical Sciences and Mathematics - Astronomy - Extragalactic Astrophysics
Principal Investigator:Laerte Sodré Junior
Grantee:Leandro José Beraldo e Silva
Home Institution: Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Associated research grant:12/00800-4 - The 3-D universe: astrophysics with large galaxy surveys, AP.TEM
Associated scholarship(s):17/01421-0 - Constraining the galactic potential with frequency analysis of the GAIA survey data, BE.EP.PD


The main goal of this project is to broaden the present understanding of the relaxation process (violent relaxation) in dark matter halos and collisionless self-gravitating systems in general, as well as to characterize, with simple theoretical models, the stationary state achieved at the end of this process. This study will use numerical siulation data, generated with the code GADGET-2, in order to test models for the velocity distribution in dark matter halos. Specifically, we will test the velocity distribution associated to the model recently proposed by us (and accepted for publication in Physical Review D), which associates the mixing level of the system with the indistinguishability of its constituents. This model also raises some doubts about the validity of the Vlasov equation during the violent relaxation, and thus we will test the validity of this equation with the simulation data. We will also test the correction to the velocity distribution due to the Landau Damping phenomenon, which is expected to occur during violent relaxation. From the observational point of view, we will use the projected density profiles of galaxy clusters, obtained via gravitational lensing, in order to test different theoretical models for the density profile. Particulalry, we will test the model called DARKexp (which was already tested with another data set), a model recently proposed (but not compared yet with observational data) which relates conserved actions and the maximum entropy principle, and finally we will test the density profile associated to the model proposed by us and cited previously.

Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
E SILVA, LEANDRO BERALDO; PEDRA, WALTER DE SIQUEIRA; VALLURI, MONICA. The Discreteness-driven Relaxation of Collisionless Gravitating Systems: Entropy Evolution and the Nyquist-Shannon Theorem. ASTROPHYSICAL JOURNAL, v. 872, n. 1 FEB 10 2019. Web of Science Citations: 0.
BERALDO E SILVA, LEANDRO; PEDRA, WALTER DE SIQUEIRA; VALLURI, MONICA; SODRE, LAERTE; BRU, JEAN-BERNARD. The Discreteness-driven Relaxation of Collisionless Gravitating Systems: Entropy Evolution in External Potentials, N-dependence, and the Role of Chaos. ASTROPHYSICAL JOURNAL, v. 870, n. 2 JAN 10 2019. Web of Science Citations: 0.
BERALDO E SILVA, LEANDRO; PEDRA, WALTER DE SIQUEIRA; SODRE, LAERTE; PERICO, EDER L. D.; LIMA, MARCOS. The Arrow of Time in the Collapse of Collisionless Self-gravitating Systems: Non-validity of the Vlasov-Poisson Equation during Violent Relaxation. ASTROPHYSICAL JOURNAL, v. 846, n. 2 SEP 10 2017. Web of Science Citations: 1.

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