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We study systematically stationary solutions to the coupled Vlasov and Poisson equations which have `self-similar' or scaling symmetry in phase space. In particular, we find analytically {\it all} spherically symmetric distribution…

Astrophysics · Physics 2015-06-24 R. N. Henriksen , Lawrence M. Widrow

A kinetic model for the dynamics of collisionless spin neutral particles in a spacetime with torsion is proposed. The fundamental matter field is the kinetic density $f(x,u,s)$ of particles with four-velocity $u$ and four-spin $s$. The…

General Relativity and Quantum Cosmology · Physics 2025-02-26 Simone Calogero

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

We provide a systematic study for the accretion of a collisionless, relativistic kinetic gas into a nonrotating black hole. To this end, we first solve the relativistic Liouville equation on a Schwarzschild background spacetime. The most…

General Relativity and Quantum Cosmology · Physics 2017-04-19 Paola Rioseco , Olivier Sarbach

We study the kinematic relative velocity of general test particles with respect to stationary observers (using spherical coordinates) in Schwarzschild spacetime, obtaining that its modulus does not depend on the observer, unlike Fermi,…

General Relativity and Quantum Cosmology · Physics 2013-01-24 Vicente J. Bolós

The periodic Lorentz gas describes an ensemble of non-interacting point particles in a periodic array of spherical scatterers. We have recently shown that, in the limit of small scatterer density (Boltzmann-Grad limit), the macroscopic…

Mathematical Physics · Physics 2008-05-17 Jens Marklof , Andreas Strombergsson

We consider a model of a dynamical Lorentz gaz : a single particle is moving in $\mathbb{R}^d$ through an array of fixed an soft scatterers each possessing an internal degree of freedom coupled to the particle. Assuming the initial velocity…

Probability · Mathematics 2018-07-04 Émilie Soret

We present an analytical and numerical study of a nonlinear diffusion model which describes density relaxation of loosely packed particles under gravity and weak random (thermal) vibration, and compare the results with Monte Carlo…

Soft Condensed Matter · Physics 2009-11-10 Jeferson J. Arenzon , Yan Levin , Mauro Sellitto

The kinetics of collisionless continuous medium is studied in a bounded region on a curved manifold. We have assumed that in statistical equilibrium, the probability distribution density depends only on the total energy. It is shown that in…

Chaotic Dynamics · Physics 2007-05-23 V. V. Kozlov

A steady self-diffusion process in a gas of hard spheres at equilibrium is analyzed. The system exhibits a constant gradient of labeled particles. Neither the concentration of these particles nor its gradient are assumed to be small. It is…

Statistical Mechanics · Physics 2015-06-17 J. Javier Brey , M. J. Ruiz-Montero

We study dynamical heterogeneity and glassy dynamics in a kinetically constrained lattice gas model which has both translational and rotational degrees of freedom. We find that the rotational diffusion constant tracks the structural…

Soft Condensed Matter · Physics 2015-06-25 Albert C. Pan

A generalized physics-based expression for the drag coefficient of spherical particles moving in a fluid is derived. The proposed correlation incorporates essential rarefied physics, low-speed hydrodynamics, and shock-wave physics to…

By combining methods of kinetic and density functional theory, we present a description of molecular fluids which accounts for their microscopic structure and thermodynamic properties as well as for the hydrodynamic behavior. We focus on…

Mesoscale and Nanoscale Physics · Physics 2015-05-18 Umberto Marini Bettolo Marconi , Simone Melchionna

A kinetic model for granular mixtures is considered to study three different non-equilibrium situations. The model is based on the equivalence between a gas of elastic hard spheres subjected to a drag force proportional to the particle…

Soft Condensed Matter · Physics 2025-02-27 Pablo Avilés , David González Méndez , Vicente Garzó

We study the dynamics of entanglement in spin gases. A spin gas consists of a (large) number of interacting particles whose random motion is described classically while their internal degrees of freedom are described quantum-mechanically.…

Quantum Physics · Physics 2007-05-23 J. Calsamiglia , L. Hartmann , W. Dür , H. -J. Briegel

We study in this work the dynamics of a granular impurity immersed in a low-density granular gas of identical particles. For description of the kinetics of the granular gas and the impurity particles we use the rough hard sphere collisional…

Soft Condensed Matter · Physics 2017-07-13 Francisco Vega Reyes , Antonio Lasanta , Andrés Santos , Vicente Garzó

The asymptotic form of the energy density for a gas of particles surrounding a sphere of mass $M$ and radius $R$ is studied using Einstein's equations. It is shown that if the pressure of the gas $p$ varies linearly with the energy density…

High Energy Physics - Phenomenology · Physics 2007-05-23 Achilles D. Speliotopoulos

We propose to use spin hydrodynamics, a two-fluid model of spin propagation, as a generalization of the diffusion equation. We show that in the dense limit spin hydrodynamics reduces to Fick's law and the diffusion equation. In the opposite…

Quantum Gases · Physics 2016-11-02 Thomas Schaefer

We study the dynamics of a particle moving in one-dimensional Lorentz lattice-gas where particle performs mainly three different kinds of motion {\it viz} ballistic motion, diffusion and confinement. There are two different types of…

Soft Condensed Matter · Physics 2021-07-15 Sameer Kumar , Shradha Mishra

We develop a general kinetic approach to studying high-frequency collective excitations in arbitrary-spin quantum gases. To this end, we formulate a many-body Hamiltonian that includes the multipolar exchange interaction as well as the…

Quantum Gases · Physics 2025-02-25 M. Bulakhov , A. S. Peletminskii , Yu. V. Slyusarenko