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We study the dynamical stability of self-gravitating systems in presence of anisotropy. In particular, we introduce a stability criterion, in terms of the adiabatic local index, that generalizes the stability condition $<\gamma> \geq 4/3$…

General Relativity and Quantum Cosmology · Physics 2022-06-29 Giuseppe Alberti

A dilute gas of hard disks confined between two straight parallel lines is considered. The distance between the two boundaries is in between one and two particle diameters, so that the system is quasi-one-dimensional. A Boltzmann-like…

Statistical Mechanics · Physics 2022-04-13 M. Mayo , J. Javier Brey , M. I. García de Soria , P. Maynar

The Boltzmann collision operator for a dilute granular gas of inelastic rough hard spheres is much more intricate than its counterpart for inelastic smooth spheres. Now the one-body distribution function depends not only on the…

Soft Condensed Matter · Physics 2014-11-10 Andrés Santos

We study long-range interacting systems driven by external stochastic forces that act collectively on all the particles constituting the system. Such a scenario is frequently encountered in the context of plasmas, self-gravitating systems,…

Statistical Mechanics · Physics 2013-12-03 Cesare Nardini , Shamik Gupta , Stefano Ruffo , Thierry Dauxois , Freddy Bouchet

We propose an approach to find out when a self-gravitating system is in a quasi-equilibrium state. This approach is based on a comparison between two quantities identifying behavior of the system: a measure of interactions intensity and the…

High Energy Physics - Theory · Physics 2022-07-26 Azizollah Azizi , Amir A. Khodahami

Granular matter under rapid flow conditions can be modeled as a granular gas, namely, a gas of hard spheres dissipating part of their kinetic energy during binary collisions (inelastic hard spheres, IHS). On the other hand, given that…

Soft Condensed Matter · Physics 2018-03-28 Moisés G. Chamorro

The one-dimensional kinetic equation with integral of collisions type BGK (Bhatnagar, Gross and Krook) and frequency of collisions affine depending on the module of molecular velocity is constructed. Laws of preservation of number of…

Mathematical Physics · Physics 2014-03-11 A. L. Bugrimov , A. V. Latyshev , A. A. Yushkanov

A kinetic model for the Boltzmann equation is proposed and explored as a practical means to investigate the properties of a dilute granular gas. It is shown that all spatially homogeneous initial distributions approach a universal…

Statistical Mechanics · Physics 2009-11-10 James W. Dufty , Aparna Baskaran , Lorena Zogaib

We propose a gravitational model with a Brans-Dicke-type scalar field having, in the would-be action, a "wrong-sign" kinetic term and a quartic interaction term. In a cosmological context, we obtain, depending on the boundary conditions,…

General Relativity and Quantum Cosmology · Physics 2020-08-14 F. R. Klinkhamer

The main purpose of this article is to provide a guide to theorems on global properties of solutions to the Einstein-Vlasov system. This system couples Einstein's equations to a kinetic matter model. Kinetic theory has been an important…

General Relativity and Quantum Cosmology · Physics 2016-10-19 Hakan Andreasson

We investigate spherically symmetric equilibrium states of the Vlasov-Poisson system, relevant in galactic dynamics. We recast the equations into a regular three-dimensional system of autonomous first order ordinary differential equations…

Mathematical Physics · Physics 2007-10-31 J. Mark Heinzle , Alan D. Rendall , Claes Uggla

We study the linearized kinetic equation of relaxation model which was proposed by Bhatnagar, Gross and Krook (also called BGK model) and solve the dispersion relation. Using the solution of the dispersion relation, we analyze the…

Solar and Stellar Astrophysics · Physics 2010-10-27 Makoto Takamoto , Shu-ichiro Inutsuka

The hypothesis of molecular chaos plays the central role in kinetic theory, which provides a closure leading to the Boltzmann equation for quantitative description of classic fluids. Yet how to properly extend it to active systems is still…

Relativistic thermodynamics is treated from the point of view of kinetic theory. It is shown that the generalized J\"uttner distribution suggested in [1] is compatible with kinetic equilibrium. The requirement of compatibility of kinetic…

General Physics · Physics 2011-07-06 P. Ván

A method for obtaining simple criteria for instabilities in kinetic theory is described and outlined, specifically for the relativistic Vlasov-Maxwell system. An important ingredient of the method is an analysis of a parametrized set of…

Analysis of PDEs · Mathematics 2014-03-03 Jonathan Ben-Artzi

In this article we focus on kinetic equations for gas mixtures since in applications one often has to deal with mixtures instead of a single gas. In particular we consider an approximation of the Boltzmann equation, the…

Analysis of PDEs · Mathematics 2022-03-30 Marlies Pirner , Sandra Warnecke

The main theme of the article is the study of discrete systems of material points subjected to constraints not only of a geometric type (holonomic constraints) but also of a kinematic type (nonholonomic constraints). The setting up of the…

Classical Physics · Physics 2023-05-30 Federico Talamucci

We describe a kinetic theory approach to quantum gravity -- by which we mean a theory of the microscopic structure of spacetime, not a theory obtained by quantizing general relativity. A figurative conception of this program is like…

General Relativity and Quantum Cosmology · Physics 2008-11-26 B. L. Hu

The cosmological dynamics are rigorously investigated through the systematic application of autonomous system analysis to the gravitational field equations in non-metricity gravity. The systematic procedure to analyze the late-time cosmic…

General Relativity and Quantum Cosmology · Physics 2025-03-13 Pooja Vishwakarma , Parth Shah , Kazuharu Bamba

The transport coefficients of a dilute gas of inelastic hard spheres immersed in a molecular gas are determined. We assume that the number density of the granular gas is much smaller than that of the surrounding molecular gas, so that the…

Soft Condensed Matter · Physics 2022-06-07 Rubén Gómez González , Vicente Garzó