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An integral relation is derived from the Fokker-Planck equation which connects the steady-state probability currents with the dynamics of relaxation on short timescales in the limit of small perturbation fields. As a consequence of this…

Statistical Mechanics · Physics 2024-03-26 Andrea Auconi

The relaxation towards equilibrium of systems with long range interactions is not yet fully understood. As a step towards such a comprehension, we propose the study of the dynamical equilibrium fluctuations in a model system with long range…

Statistical Mechanics · Physics 2009-11-10 Freddy Bouchet

In an effort to better understand collisionless relaxation processes in gravitational systems, we investigate one-dimensional models. Taking advantage of a Hermite-Legendre expansion of relevant distribution functions, we present analytical…

Astrophysics of Galaxies · Physics 2019-06-12 Eric I. Barnes , Robert J. Ragan

A quasi-two-dimensional system of hard spheres strongly confined between two parallel plates is considered. The attention is focussed on the macroscopic self-diffusion process observed when the system is looked from above or from below. The…

Statistical Mechanics · Physics 2020-01-09 J. Javier Brey , M. I. García de Soria , P. Maynar

We discuss the dynamics and thermodynamics of systems with weak long-range interactions. Generically, these systems experience a violent collisionless relaxation in the Vlasov regime leading to a (usually) non-Boltzmannian quasi stationary…

Statistical Mechanics · Physics 2009-11-13 Pierre-Henri Chavanis

We derive approximate iterative analytical solutions of the non-extensive Boltzmann transport equation in the relaxation time approximation. The approximate solutions almost overlap with the exact solution for a considerably wide range of…

Nuclear Theory · Physics 2023-06-27 Trambak Bhattacharyya

We study the relaxation of a test particle immersed in a bath of field particles interacting via weak long-range forces. To order 1/N in the $N\to +\infty$ limit, the velocity distribution of the test particle satisfies a Fokker-Planck…

Statistical Mechanics · Physics 2009-11-11 P. H. Chavanis

Long-range interacting Hamiltonian systems are believed to relax generically towards non-equilibrium states called "quasi-stationary" because they evolve towards thermodynamic equilibrium very slowly, on a time-scale diverging with particle…

Statistical Mechanics · Physics 2017-07-18 Michael Joyce , Jules Morand , Pascal Viot

We propose fractional Fokker-Planck equation for the kinetic description of relaxation and superdiffusion processes in constant magnetic and random electric fields. We assume that the random electric field acting on a test charged particle…

Plasma Physics · Physics 2009-11-07 A. Chechkin , V. Gonchar , M. Szydlowski

"Quasi-stationary" states are approximately time-independent out of equilibrium states which have been observed in a variety of systems of particles interacting by long-range interactions. We investigate here the conditions of their…

Statistical Mechanics · Physics 2010-12-03 Andrea Gabrielli , Michael Joyce , Bruno Marcos

Inspired by one--dimensional light--particle systems, the dynamics of a non-Hamiltonian system with long--range forces is investigated. While the molecular dynamics does not reach an equilibrium state, it may be approximated in the…

Statistical Mechanics · Physics 2019-01-23 Romain Bachelard , Nicola Piovella , Shamik Gupta

The local balance equations for the density, momentum, and energy of a dilute gas of elastic or inelastic hard spheres, strongly confined between two parallel hard plates are obtained. The starting point is a Boltzmann-like kinetic…

Statistical Mechanics · Physics 2020-04-22 J. Javier Brey , P. Maynar , M. I. García de Soria

We complete the kinetic theory of inhomogeneous systems with long-range interactions initiated in previous works. We use a simpler and more physical formalism. We consider a system of particles submitted to a small external stochastic…

Statistical Mechanics · Physics 2023-08-23 Pierre-Henri Chavanis

A quasi-distribution function in phase space (based on Wigner functions) is used to write down the quantum version of Boltzmann equation (Wigner-Boltzmann transport equation). The relaxation time approximation is show to be a good approach…

Statistical Mechanics · Physics 2015-12-21 Aldo R. Fernandes Nt

We discuss the dynamics and thermodynamics of systems with long-range interactions. We contrast the microcanonical description of an isolated Hamiltonian system to the canonical description of a stochastically forced Brownian system. We…

Statistical Mechanics · Physics 2009-11-10 Pierre-Henri Chavanis

We briefly review some equilibrium and nonequilibrium properties of systems with long-range interactions. Such systems, which are characterized by a potential that weakly decays at large distances, have striking properties at equilibrium,…

Statistical Mechanics · Physics 2009-11-13 Stefano Ruffo

We study long-range interacting systems perturbed by external stochastic forces. Unlike the case of short-range systems, where stochastic forces usually act locally on each particle, here we consider perturbations by external stochastic…

Statistical Mechanics · Physics 2013-12-04 Cesare Nardini , Shamik Gupta , Stefano Ruffo , Thierry Dauxois , Freddy Bouchet

We review and complete the existing literature on the kinetic theory of spatially homogeneous systems with long-range interactions taking collective effects into account. The evolution of the system as a whole is described by the…

Statistical Mechanics · Physics 2012-02-20 Pierre-Henri Chavanis

The Vlasov-Nordstr\"{o}m-Fokker-Planck system describes the evolution of self-gravitating matter experiencing collisions with a fixed background of particles in the framework of a relativistic scalar theory of gravitation. We study the…

Mathematical Physics · Physics 2014-07-22 José Antonio Alcántara Felix , Simone Calogero , Stephen Pankavich

We present the Multi-Particle-Collision (MPC) dynamics approach to simulate properties of low-dimensional systems. In particular, we illustrate the method for a simple model: a one-dimensional gas of point particles interacting through…