Ce papier porte sur l’étude mathématique d’une équation du type de Grad-Mercier qui décrit, dans certaines circonstances, l’équilibre d’un plasma confiné [H. Grad, P.N. Hu et D.C. Stevens, Proc. Nat. Acad. Sci. USA, 72,n${}^{\circ }$10 (1975), 3789–3793, C. Mercier, Publication of Euratom, CEA, Luxembourg (1974), C. Mercier, Communications personnelles à R. Temam et aux auteurs]. Il s’agit de trouver une fonction “régulière” $u$ solution du système$$\left\{\begin{array}{cc}-\Delta u+\lambda g\left[\delta \right(u\left)\right]=0\hfill & \text{dans}\Omega ,\hfill \\ u=\text{constante}\text{(inconnue)}\>0\hfill & \text{sur}\partial \Omega ,\hfill \\ {\int }_{\partial \Omega }\frac{\partial u}{\partial n}=I,\hfill \end{array}\right.$$où $\Omega$ est un ouvert borné régulier de ${\mathbf{R}}^n$, et$$\delta \left(u\right)\left(x\right)=\mathrm{mes}\{y\in \Omega \mid u(x)\<u(y)\<0\}.$$L’opérateur non linéaire...

We study an atomistic pair potential-energy E(n)(y) that describes the elastic behavior of two-dimensional crystals with natoms where $y\in {ℝ}^{2\times n}$ characterizes the particle positions. The main focus is the asymptotic analysis of the ground state energy asn tends to infinity. We show in a suitable scaling regime where the energy is essentially quadratic that the energy minimum of E(n) admits an asymptotic expansion involving fractional powers of n: ${\min }_y{E}^{\left(n\right)}\left(y\right)=n{E}_{\mathrm{bulk}}+\sqrt{n}{E}_{\mathrm{surface}}+o\left(\sqrt{n}\right),n\to \infty .$ The bulk energy densityEbulk is given by an explicit expression...

We study an atomistic pair potential-energy E(n)(y) that describes the elastic behavior of two-dimensional crystals with n atoms where $y\in {ℝ}^{2\times n}$ characterizes the particle positions. The main focus is the asymptotic analysis of the ground state energy as n tends to infinity. We show in a suitable scaling regime where the energy is essentially quadratic that the energy minimum of E(n) admits an asymptotic expansion involving fractional powers of n: ${\min }_y{E}^{\left(n\right)}\left(y\right)=n{E}_{\mathrm{bulk}}+\sqrt{n}{E}_{\mathrm{surface}}+o\left(\sqrt{n}\right),n\to \infty .$ The bulk energy density Ebulk is given by an explicit expression...

The main objective of this paper is to present a new probabilistic model underlying the universal relaxation laws observed in many fields of science where we associate the survival probability of the system's state with the defect-diffusion framework. Our approach is based on the notion of the continuous-time random walk. To derive the properties of the survival probability of a system we explore the limit theorems concerning either the summation or the extremes: maxima and minima. The forms of...

The Hamiltonian for an extended Hubbard model with phonons as introduced by A. Montorsi and M. Rasetti is considered on a D-dimensional lattice. The symmetries of the model are studied in various cases. It is shown that for a certain choice of the parameters a superconducting $S{U}_q\left(2\right)$ holds as a true quantum symmetry, but only for D=1.

We study some properties of the k-symplectic Hamiltonian systems in analogy with the well-known classical Hamiltonian systems. The integrability of k-symplectic Hamiltonian systems and the relationships with the Nambu's statistical mechanics are given.

Systems with Coulomb and logarithmic interactions arise in various settings: an instance is the classical Coulomb gas which in some cases happens to be a random matrix ensemble, another is vortices in the Ginzburg-Landau model of superconductivity, where one observes in certain regimes the emergence of densely packed point vortices forming perfect triangular lattice patterns named Abrikosov lattices, a third is the study of Fekete points which arise in approximation theory. In this review, we describe...

Consider a random environment in ${\mathbb{Z}}^d$ given by i.i.d. conductances. In this work, we obtain tail estimates for the fluctuations about the mean for the following characteristics of the environment: the effective conductance between opposite faces of a cube, the diffusion matrices of periodized environments and the spectral gap of the random walk in a finite cube.