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A Langevin Description for Driven Granular Gases

P. Maynar, M. I. García de Soria (2011)

Mathematical Modelling of Natural Phenomena

The study of the fluctuations in the steady state of a heated granular system is reviewed. A Boltzmann-Langevin description can be built requiring consistency with the equations for the one- and two-particle correlation functions. From the Boltzmann-Langevin equation, Langevin equations for the total energy and the transverse velocity field are derived. The existence of a fluctuation-dissipation relation for the transverse velocity field is also...

Application of the Method of Generating Functions to the Derivation of Grad’s N-Moment Equations for a Granular Gas

S. H. Noskowicz, D. Serero (2011)

Mathematical Modelling of Natural Phenomena

A computer aided method using symbolic computations that enables the calculation of the source terms (Boltzmann) in Grad’s method of moments is presented. The method is extremely powerful, easy to program and allows the derivation of balance equations to very high moments (limited only by computer resources). For sake of demonstration the method is applied to a simple case: the one-dimensional stationary granular gas under gravity. The method should...

Explicit spectral gap estimates for the linearized Boltzmann and Landau operators with hard potentials.

Céline Baranger, Clément Mouhot (2005)

Revista Matemática Iberoamericana

This paper deals with explicit spectral gap estimates for the linearized Boltzmann operator with hard potentials (and hard spheres). We prove that it can be reduced to the Maxwellian case, for which explicit estimates are already known. Such a method is constructive, does not rely on Weyl's Theorem and thus does not require Grad's splitting. The more physical idea of the proof is to use geometrical properties of the whole collision operator. In a second part, we use the fact that the Landau operator...

Gravitational collapse of a Brownian gas

Clément Sire, Pierre-Henri Chavanis (2004)

Banach Center Publications

We investigate a model describing the dynamics of a gas of self-gravitating Brownian particles. This model can also have applications for the chemotaxis of bacterial populations. We focus here on the collapse phase obtained at sufficiently low temperature/energy and on the post-collapse regime following the singular time where the central density diverges. Several analytical results are illustrated by numerical simulations.

Hydrodynamics of Inelastic Maxwell Models

V. Garzó, A. Santos (2011)

Mathematical Modelling of Natural Phenomena

An overview of recent results pertaining to the hydrodynamic description (both Newtonian and non-Newtonian) of granular gases described by the Boltzmann equation for inelastic Maxwell models is presented. The use of this mathematical model allows us to get exact results for different problems. First, the Navier–Stokes constitutive equations with explicit expressions for the corresponding transport coefficients are derived by applying the Chapman–Enskog...

Kinetic equations with Maxwell boundary conditions

Stéphane Mischler (2010)

Annales scientifiques de l'École Normale Supérieure

We prove global stability results of DiPerna-Lionsrenormalized solutions for the initial boundary value problem associated to some kinetic equations, from which existence results classically follow. The (possibly nonlinear) boundary conditions are completely or partially diffuse, which includes the so-called Maxwell boundary conditions, and we prove that it is realized (it is not only a boundary inequality condition as it has been established in previous works). We are able to deal with Boltzmann,...

The non-linear macroscopic model of Relativistic Extended Thermodynamics of an ultra-relativistic gas

Francesco Borghero, Sebastiano Pennisi (2004)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

The model for an ultra-relativistic gas is here considered in the framework of Extended Thermodynamics. The closure, satisfying exactly the principles of relativity and of entropy, is obtained by following the approach «at a macroscopic level». Our results are compared with the ones of the kinetic approach.

Un teorema de mecánica estadística relativista y los espacios de Hilbert-Lobatschewsky.

Darío Maravall Casesnoves (1985)

Trabajos de Estadística e Investigación Operativa

Se expone la geometría diferencial del espacio de las velocidades relativistas y se obtiene la función de distribución de velocidades de un gas de partículas relativistas, que modifica la función de Maxwell de Mecánica Estadística Clásica. Se introducen los espacios de Hilbert-Lobatschewsky.

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