Théorèmes d'existence pour les modifications analytiques

Sans résumé     

Théorèmes sur les groupes de substitutions

Sans résumé     

Un isomorphisme de type Deligne–Riemann–Roch

We prove an Adams–Riemann–Roch theorem for projective morphisms between regular schemes, in the sense of the program of P. Deligne on the functorial Riemann–Roch theorem and we deduce some geometric consequences. To cite this article: D. Eriksson, C. R. Acad. Sci. Paris, Ser. I 347 (2009).     

Théorèmes d’approximation pour les sections différentiables

Resume Le principail résultat de ce travail est un Théorème d’approximation des sections différentiables d’un fibré linéaireF sur un espace analytique réel cohérentX. (I) On définit le concept de sections différentiables d’un tel fibré puis le faisceau des germes de sections différentiablesC ^∞ (F) qui s’identifie àF ^∞=F⊗ _Ox C _X ^∞ :F=dual du fibré linéaireF,C _X ^∞ =faisceau des germes de fonctions différentiables surX. (II)X est supposé en plus paracompact et localement compact. On construit surF ^∞(X) une ?topologie de Whitney? pour laquelleF(X) est dense dansF ^∞(X). La démonstration utilise les complexifiés et et les voisinages de Stein deX dans .

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Sunto Il risultato principale di questo lavoro è un teorema di approssimazione delle sezioni differenziabili di un fibrato lineareF su uno spazio analitico reale coerenteX. (I) Si definisce il concetto di sezione differenziabile di un tale fibrato poi il fascio dei germi delle sezioni differenziabiliC ^∞ (F) che si identifica aF ^∞=F⊗ _Ox C _X ^∞ :F=duale del fibrato lineareF,C _X ^∞ dei germi delle funzioni differenziabili suX. (II)X è supposto inoltre paracompatto e localmente compatto. Si costruisce suF ^∞ (X) una ?topologia di Whitney? per la qualeF(X è denso inF ^∞(X). La dimostrazione utilizza i complessificati e e gli intomi di Stein diX in .

     

Problèmes de Skolem sur les champs algébriques

We extend Rumely's local-global principle (as refined by Cantor, Roquette, and the author, i.e. with local splitting conditions) to the case of algebraic stacks, in Artin's sense, over rings of (S-)integers of global fields. The nongeometrically connected case is also taken into account, as well as (in some instances) the case where local conditions are imposed at all places.     

Théorème de Poincaré–Alexander pour les domaines modèles

The Poincaré–Alexander Theorem states that holomorphic mappings defined on an open subset of the unit ball of ${\mathbb{C}}^n$ may, under certain conditions, be extended to a biholomorphism of the unit ball. In a complex manifold, every strongly pseudoconvex homogeneous domain is biholomorphic to the unit ball. In an almost complex manifold, the unit ball is not the only strongly pseudoconvex homogeneous domain. A strongly pseudoconvex homogeneous domain is biholomorphic to a model domain. The aim of this paper is to extend this theorem to model domains.     

Théorèmes de dualité pour les corps de fonctions sur des corps locaux supérieurs

Let K be the function field of a smooth projective curve X over a higher-dimensional local field k. We define Tate-Shafarevich groups of a commutative group scheme via cohomology classes locally trivial at each completion of K coming from a closed point of X. We establish duality theorems between Tate-Shafarevich groups for finite groups schemes and for tori.     

Théorèmes de finitude en cohomologie galoisienne

Sans résumé A Georges de Rham,à l’occasion de son soixantième anniversaire     

Théorème KAM faible et théorie de Mather sur les systèmes lagrangiens

We give a weak version of the Kolmogorov-Arnold-Moser theorem In the framework of Mather's theory of Lagrangian systems. A particular case has already been established by Lions, Papanicolaou and Varadhan.     

Un théorème de Vitali-Hahn-Saks pour les semimartingales

Summary Let (, , P) be a complete probability space; let _t0 be an increasing right-continuous family of -complete sub--fields of ; let be a sequence of semimartingales. Assume that for all positive t and for all bounded predictable processes H, the r.v.'s converge in probability to a limit J(t, H) when n tends to infinity. Then there exists a semimartingale X such that, for all t and H, J(t, H)= .     

Couplages croissants pour les systèmes de particles interactives

Classical stochastic comparison results for spin systems are generalized to more complex interacting particle systems. The state space of each site is a finite partially ordered set and several sites may simultaneously change status. Two ways of obtaining comparison conditions are considered. The first one consists in adapting to interacting particle systems a result by Massey for Markov processes on countable spaces. The second is based on the explicit construction of Markov couplings. In particular, a generalization of the Vasershtein coupling for spin systems is used.     

Convergence des méthodes particulaires renormalisées pour les systèmes de Friedrichs

We present a study of the renormalized particle scheme. Renormalization is a tool introduced in order to alleviate the SPH particle methods' lack of consistency. A conservative scheme, the weak renormalized scheme, is derived from the general conservation laws weak formulation. We apply this scheme to Friedrichs systems. The weak renormalized scheme being unstable, we introduce a numerical viscosity before applying an explicit Euler time discretization, and thus construct the numerical scheme whose convergence in $L^2$ norm is studied. To cite this article: N. Lanson, J.-P. Vila, C. R. Acad. Sci. Paris, Ser. I 340 (2005).     

Un théorème de Choquet-Deny pour les groupes moyennables

Résumé SoitG un groupe moyennable connexe, locallement compact, à base dénombrable. Soit une mesure positive sur les boréliens deG. Nous étudions les fonctions boréliennes positivesh vérifiant: g G, . Sous de bonnes hypothèses sur , nous obtenons, pour ces fonctions, une représentation intégrale à l'aide d'exponentielles.

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Summary LetG be a connected locally compact separable amenable group. Let be a positive measure on the Borel -field ofG. We study the positive Borel functionsh onG which satisfy: g G, . Under smooth assumptions on , we establish an integral representation of these functions in term of exponentials.