One-Dimensional Pressureless Gas Systems with/without Viscosity

A general global existence result for one-dimensional pressureless Euler/Euler-Poisson systems with or without viscosity is obtained by employing the “sticky particles” model. We first construct entropy solutions for some appropriate scalar conservation laws, then we show that these solutions encode all the information necessary to obtain solutions for the pressureless systems. Another novel contribution is the stability and uniqueness of solutions, which is obtained via a contraction principle in the Wasserstein metric.     

Quasineutral limit of the pressureless Euler–Poisson equation

In this short paper, we consider the quasineutral limit for the pressureless Euler–Poisson system for ions. By applying the modulated energy method, it shows that the weak solutions for the Euler–Poisson system converge weakly to the strong solutions of the compressible Euler equation as the Debye length tends to zero.     

Free transportation cost inequalities via random matrix approximation

By means of random matrix approximation procedure, we re-prove Biane and Voiculescus free analog of Talagrands transportation cost inequality for measures on R in a more general setup. Furthermore, we prove the free transportation cost inequality for measures on T as well by extending the method to special unitary random matrices.Supported in part by Grant-in-Aid for Scientific Research (C)14540198 and by the program R&D support scheme for funding selected IT proposals of the Ministry of Public Management, Home Affairs, Posts and Telecommunications.Supported in part by MTA-JSPS project (Quantum Probability and Information Theory) and by OTKA T032662.Supported in part by Grant-in-Aid for Young Scientists (B)14740118.Mathematics Subject Classification (2000): Primary: 46L54, 46L53; Secondary: 60F10, 15A52, 94A17.     

On large deviations for some sequences of weighted means of Gaussian processes

In this paper we study some sequences of weighted means of continuous real valued Gaussian processes. More precisely we consider suitable generalizations of both arithmetic and logarithmic means of a Gaussian process with covariance function which satisfies either an exponential decay condition or a power decay condition. Our aim is to provide limits of variances of functionals of such weighted means which allow the application of some large deviation results in the literature.     

Régularité des solutions d'un problème mêlé Dirichlet–Signorini dans un domaine polygonal plan

We prove a rgularity result, in Hölder spaces, for solutions to an elliptic problem with mixed boundary condition, namely Dirichlet on a part of the boundary and Signorini on the remaining part, in a regular or polygonal, domain of IR² We give the behaviour of the solution near points where the boundary condition tyoe changes.

Nous montrons la Régularité jusqu'au bord, dans les espaces de Hölder des solutions d'un problème aux limites de type mêlé avec une condition de Dirichlet sur une partie de la frontière et des conditions de type Signorini sur le complémentaire, et ceci dans un ouvert plan ré gulier ou polygonal. Nous donnons en particulier le comportement de la solution au volisinge d'un point de la frontiére où la condition aux limites change de type.

Mots Clés: In´quations variationnells–conditions unilatélrales. Domains polygonaux.

Classification AMS 35 (J) 49 (A)     

Strict contractivity of the 2-Wasserstein distance for the porous medium equation by mass-centering

We show that the Euclidean Wasserstein distance between two compactly supported solutions of the one-dimensional porous medium equation having the same center of mass decays to zero for large times. As a consequence, we detect an improved -rate of convergence of solutions of the one-dimensional porous medium equation towards well-centered self-similar Barenblatt profiles, as time goes to infinity.

     

Hydrodynamic limit for the velocity-flip model

We study the diffusive scaling limit for a chain of N$N$ coupled oscillators. In order to provide the system with good ergodic properties, we perturb the Hamiltonian dynamics with random flips of velocities, so that the energy is locally conserved. We derive the hydrodynamic equations by estimating the relative entropy with respect to the local equilibrium state, modified by a correction term.     

Hydrodynamic limits: some improvements of the relative entropy method

The present paper is devoted to the study of the incompressible Euler limit of the Boltzmann equation via the relative entropy method. It extends the convergence result for well-prepared initial data obtained by the author in [L. Saint-Raymond, Convergence of solutions to the Boltzmann equation in the incompressible Euler limit, Arch. Ration. Mech. Anal. 166 (2003) 47–80]. It explains especially how to take into account the acoustic waves and relaxation layer, and thus to obtain convergence results under weak assumptions on the initial data.     

From the Vlasov–Poisson equation with strong local alignment to the pressureless Euler–Poisson system

This article provides a rigorous justification on a hydrodynamic limit from the Vlasov–Poisson system with strong local alignment to the pressureless Euler–Poisson system for repulsive dynamics.     

Convergence to self-similarity for the Boltzmann equation for strongly inelastic Maxwell molecules

We prove propagation of regularity, uniformly in time, for the scaled solutions of the inelastic Maxwell model for any value of the coefficient of restitution. The result follows from the uniform in time control of the tails of the Fourier transform of the solution, normalized in order to have constant energy. By standard arguments this implies the convergence of the scaled solution towards the stationary state in Sobolev and L¹$L^1$ norms in the case of regular initial data as well as the convergence of the original solution to the corresponding self-similar cooling state. In the case of weak inelasticity, similar results have been established by Carlen, Carrillo and Carvalho (2009) in [11] via a precise control of the growth of the Fisher information.