Compléments à un Résultat de Safarevic

It is shown that if the dilatation tensor G f of a space quasi regular mapping f belongs to the space VMO (vanishing mean oscillation), then f is a local homeomorphism. The same is true If the BMO-norm of G _f is small or if G_f is only close to the VMO space in the BMO-norm.     

Approximation dans un Problème de Viscoélasticité Périodique

We are concerned with equations which derive from a quasistatic periodic problem of viscoelasticity. We give a condition which yields to existence and uniqueness of a periodic solution. Then we prove a finite element method based on equilibrium elements for the space approximation and on the explicit Euler scheme for the time approximation.     

Comparaison des deux composantes d''un subordinateur bivarié, puis étude de l''enveloppe supérieure d''un processus de Lévy

Soit (Y,Z) un subordinateur bivarié. Nous donnons une condition suffisante pour que Y_t/Z_t converge vers zéro quand t tend vers 0 ou +∞. Ceci généralise partiellement des résultats de Bertoin et de Kesten–Erickson.Soit X un processus de Lévy et S_t=sup{X_s: st}. Soit f une fonction sous-additive. En appliquant le résultat précédent au subordinateur bivarié d'échelle, nous donnons des conditions nécéssaires et suffisantes pour que et égalent 0 ou +∞.Let (Y,Z) be a bivariate subordinator. Generalizing theorems of Bertoin and Kesten–Erickson, we give a sufficient condition for Y_t/Z_t to converge to 0 when t tends either to 0 or +∞.Let X be a Lévy process. Denote by S_t=sup{X_s: st} and let f be any sub-additive function. Applying our first result to the bivariate ladder process, we give necessary and sufficient conditions for and to be either 0 or +∞.     

Intégrabilité au sens de Cauchy et -intégrabilité pour des applications à valeurs dans un espace de Banach

The equivalence between the Cauchy left-integrability and the Riemann-integrability, for a bounded function defined on a compact interval of with values in a Banach space, is a particular case of Theorem 2.1. A first generalization to the case of functions defined on a compact rectangle of ² is given by Theorem 2.5.     

Opérateurs différentiels linéaires à coefficients constants et schémas de Hilbert ponctuels

We use algebraic methods to study systems of linear partial differential equations with constant coefficients. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Estimation de Yule–Walker d'un CAR(p) observé à temps discret

Let (X(lδ), l=0,n) be a discrete observation at mesh δ>0 of X, a CAR(p). Classical Yule–Walker estimation are biased and must be corrected. Resultant estimators converge if T=nδ→+∞, are asymptotically normal with rate , and efficient. The diffusion coefficient is also estimated, with rate .     

Une étude mathématique d'un modèle de Rotenberg

In this paper, a cell proliferation model of Rotenberg is mathematically studied. Each cell of this population is distinguished by its degree of maturity μ and its maturation velocity v. We equipped this mathematical model by boundary conditions wich generalize all biological rules imposed by Rotenberg. We show that this model is governed by a strongly continuous semigroup. We also develop some properties of this semigroup and we study its asymptotic behaviour in the uniform topology.     

Using Symmetries à Rebours

We consider nonclassical symmetries of partial differential equations (PDEs) in dimensions. Given a th‐order ordinary differential equation in the unknown we are able to find the most general scalar PDE of a given order which can be reduced via a nonclassical symmetry to .     

Sur la détermination d'une relation binaire à partir d'informations locales

This paper deals with the problematic aspect of the reconstruction of binary relations: it includes all the questions raising the possibility or impossibility to determine a structure by gathering given substructures. It is the continuation of three studies: the first made by G. Lopez [9] in 1972 about the determination of a binary relation through the types of isomorphism of its restrictions, the second made by K. B. Reid and C. Thomassen [15] in 1976 about the strongly self-complementary tournaments (every subtournament is self-complementary), the third made by C. Thomassen [16] in 1989 about the cycle space of a tournament. In the second section, we use the notion of class of difference (which was introduced in [9]) to extend a study made in [16] to binary relations. Then, in the third section, we improve the result of this last study in the case of the tournaments. After noticing that the result of [15] inferred itself naturally from the approach developed in [9], we extend, in the fourth section, the study made in [15] to binary relations.     

Fonctions de Morse sur les espaces exotiques

Summary It is shown that on an exotique space V_2n−1 of Kervaire type, we can construct a Morse function having only four critical points, the maximum, the minimum and two points of index n−1 and n.

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Entrata in Redazione il 20 ottobre 1972.     

Une résolution élémentaire de l'équation diophantienne x = y − 1

A complete solution in integers of the well-known diophantine equation y² = x³ + 1 is given by using elementary arguments based on the Pell-Fermat equation X² − 3Y² = 1.     

Indicatrices de Croissance des Fonctions Entières de N-Variables

Sans résumé     

L'intégration graphique des équations différentielles ordinaires

In the period which precedes the appearance of computers, needs in calculation of the scientists and engineers led to an important development of graphic methods of integration. To contribute to the study of this little known phenomenon, the article presents techniques and instruments used for the graphic integration of ordinary differential equations, and looks for their historic origins by going back to the beginning of calculus: processes of geometric calculation by the polygonal method or the method of radius of curvature, use of tractional motion for the conception of integraphs, reduction to graphic quadratures in finite or infinite number.     

Quelques Formules d'Inversion à Plusieurs Variables

In this paper, we use divided differences to give algebraic identities involving a finite number of infinite sets of variables (Propositions 6, 7, and 12). Specializing the sets of variables, we recover the formulas of Carlitz (Corollaries 15 and 20), and an inversion formula of Chu Wenchang (Corollary 16). We also prove a q-analog of their results, and we give a mixed case (Proposition 19).     

Fonctions qui operent sur les espaces de Besov

Soient , et trois réels tels que , , et et soit une fonction appartenant à l'espace de Besov . Nous montrons que si est une fonction, de la variable réelle, nulle à l'origine, lipschitzienne et appartenant à l'espace on a alors . La preuve est essentiellement basée sur des résultats d'approximation par des fonctions splines de degré .