Hard spheres dynamics: weak vs hard collisions

利用碰撞树和半群从硬球 Rayleigh 气体推导动力学方程与扩散方程

Derivation of kinetic and diffusion equations from a hard-sphere Rayleigh gas using collision trees and semigroups

本文在 Boltzmann-Grad 极限下研究硬球 Rayleigh 气体，借助碰撞树上的半群方法证明经验粒子动力学收敛于 Boltzmann 型动力学，并经进一步重标度导出扩散方程。

Approaches to Derivation of the Boltzmann Equation with Hard Sphere Collisions

In the paper the possible approaches to the rigorous derivation of the Boltzmann kinetic equation with hard sphere collisions from underlying dynamics are considered. In particular, a formalism for the description of the evolution of infinitely many hard spheres within the framework of marginal observables in the Boltzmann--Grad scaling limit is developed. Also we give consideration to one more approach of the description of the kinetic evolution of hard spheres in terms of a one-particle distribution function governed by the non-Markovian generalization of the Enskog equation and the Boltzman…

Attractive Riesz potentials acting on hard spheres

In this paper we introduce a model for hard spheres interacting through attractive Riesz type potentials, and we study its thermodynamic limit. We show that the tail energy enforces optimal packing and round macroscopic shapes.

Compressible Navier--Stokes system with the hard sphere pressure law in an exterior domain

We consider the motion of compressible Navier-Stokes fluids with the hard sphere pressure law around a rigid obstacle when the velocity and the density at infinity are non zero. This kind of pressure model is largely employed in various physical and industrial applications. We prove the existence of weak solution to the system in the exterior domain.

On Microscopic Origin of the Fokker - Planck Kinetic Evolution of Hard Spheres

The rigorous approach to the description of the kinetic evolution of a many-particle system composed of a trace hard sphere and an environment of finitely many hard spheres is developed. We prove that the evolution of states of a trace hard sphere in an environment can be described within the framework of the marginal distribution function governed by the generalized Fokker -- Planck kinetic equation and an infinite sequence of the explicitly defined functionals of this function.

Long time validity of the linearized Boltzmann equation for hard spheres: a proof without billiard theory

We study space-time fluctuations of a hard sphere system at thermal equilibrium, and prove that the covariance converges to the solution of a linearized Boltzmann equation in the low density limit, globally in time. This result has been obtained previously in [7], by using uniform bounds on the number of recollisions of dispersing systems of hard spheres (as provided for instance in [9]). We present a self-contained proof with substantial differences, which does not use this geometric result. This can be regarded as the first step of a program aiming to derive the fluctuation theory of the rar…