Une nouvelle définition de l'invariant de CassonA new definition of the Casson invariant

In [4], following [2], we have defined an invariant $\text{Δ(f)∈}\text{Q}$, for any $\text{f∈}\text{M}{}_{\mathrm{g,1}}$, the mapping class group of a compact, connected, oriented surface with connected boundary, genus g. For $\text{f∈}\text{T}{}_{\mathrm{g,1}}$ (a certain subgroup of the Torelli group), we have shown in [4], using Casson surgery formula, that Δ(f) co??ncides with the Casson invariant [1] of the homology sphere M_f, obtained by gluing two handlebodies along f. The purpose of this Note is to prove directly (i.e., without reference to Casson) that Δ(f), for $\text{f∈}\text{T}{}_{\mathrm{g,1}}$, depends only on M_f. The surgery formula, which is a difficult point in Casson version, follows almost immediatly from the definition of Δ(f). To cite this article: B. Perron, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 199–204.     

Construction inconditionnelle de groupes de Galois motiviquesAn unconditional construction of motivic Galois groups

We attach to any “classical” Weil cohomology theory over a field a motivic Galois group, defined up to an inner automorphism. We also study the specialisation of numerical motives and the behaviour of motivic Galois group by specialisation. To cite this article: Y. André, B. Kahn, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 989–994.     

Une suite spectrale de Hochschild–Serre pour l'uniformisation de Rapoport–ZinkAn Hochschild–Serre spectral sequence for the Rapoport–Zink uniformization

In this Note we announce results concerning the first part of a programme intending to generalize the articles [5,7] and thus construct local Langlands correspondences for groups other than GL_n (for example, quasisplit unitary groups) inside the ? adic cohomology of Rapoport–Zink spaces. The method consists in comparing the cohomology of these local objects with that of global objects: Shimura varieties. For this we generalize the spectral sequences constructed in [5] and [4]. A part of these results is quoted in [6]. To cite this article: L. Fargues, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 739–742.     

Une remarque sur les ensembles hyperboliques localement maximauxA remark on locally maximal hyperbolic sets

On an example we show that there exist some hyperbolic sets which are not contained in any locally maximal hyperbolic set. To cite this article: S. Crovisier, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 401–404.     

Demi-reconstruction de l'opérateur clôture transitiveHalf-reconstruction of the operator transitive closure

Boudabbous and Cherif [1] showed that the operator transitive closure is reconstructible in the sense of Fraïssé and of Ulam. We examine the analagous problem in the terms of half-reconstruction. To cite this article: I. Boudabbous, J. Dammak, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 257–260.     

Sur l'η-expansion infinieOn infinite η-expansion

We give two characterizations of the ordering on Böhm trees induced by the D_∞ model, one of which formalizes a continuity property of infinite η-expansion: $\text{A}\text{?}{}_{\mathrm{\infty }}\text{B}$ if for any finite approximant A of $\text{A}$ there exists a finite approximant B of $\text{B}$ such that A is a sub-tree of B, modulo finitely many η-equalities and finitely many infinite η-expansions of variables. To cite this article: P.-L. Curien, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 77–82     

Support of Virasoro unitarizing measuresSupport des mesures unitarisantes de l'algèbre de Virasoro

A unitarizing measure is a probability measure such that the associated L² space contains a closed subspace of holomorphic functionals on which the Virasoro algebra acts unitarily. It has been shown that the unitarizing property is equivalent to an a priori given formula of integration by parts, which has been computed explicitly. We show in this Note that unitarizing measures must be supported by the quotient of the homeomorphism group of the circle by the subgroup of Möbius transformations. To cite this article: H. Airault et al., C. R. Acad. Sci. Paris, Ser. I 335 (2002) 621–626.     

Une décomposition prismatique de l'opérade de Barratt–EcclesA prismatic decomposition of the Barratt–Eccles operad

The Barratt–Eccles operad is a simplicial operad formed by the classical homogeneous bar construction of symmetric groups. We prove that these simplicial sets decompose as unions of prisms indexed by surjections. We observe that the cellular complexes given by this prismatic structure are nothing but the components of the surjection operad (the operad introduced by J. McClure and J. Smith in their work on the Deligne conjecture). To cite this article: C. Berger, B. Fresse, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 365–370.     

Arbres de Markov couplePairwise Markov trees

The Hidden Markov Chain (HMC) models are widely applied in various problems. This succes is mainly due to the fact that the hidden model distribution conditional on observations remains a Markov chain distribution, and thus different processings, like Bayesian restorations, are handleable. These models have been recetly generalized to “Pairwise” Markov chains, which admit the same processing power and a better modeling one. The aim of this Note is to show that the Hidden Markov trees, which can be seen as extensions of the HMC models, can also be generalized to “Pairwise” Markov trees, which present the same processing advantages and better modelling power. To cite this article: W. Pieczynski, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 79–82.     

Comportement asymptotique semiclassique de l'amplitude de diffusion pour des perturbations captivesSemi-classical behavior of the scattering amplitude for trapping perturbations

We study the semi-classical behavior when h→0, of the scattering amplitude f(θ,ω,λ,h) associated to the Schrödinger operator $\text{P(h)=?}\text{1}\text{2}\text{h}{}^2\text{Δ+V(x)}$ for short range perturbations V(x). We show that if we modify the potential V(x) in a domain contained in {x:V(x)>λ}, the scattering amplitude f(θ,ω,λ,h) is changed by a term of order O(h^∞). Moreover, under an additional escape assumption, we get an asymptotics of the scattering amplitude. To cite this article: L. Michel, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 655–660.     

La valeur optimale des programmes entiersThe optimal value of integer programs

We present a formula for the optimal value f_c(y) of the integer program $\text{max}\text{{c′x∣x∈}\text{Ω}\text{(y)∩}\text{N}{}^{\mathrm{n}}\text{}}$ where $\text{Ω}\text{(y)}$ is the convex polyhedron $\text{{x∈}\text{R}{}^{\mathrm{n}}\text{∣Ax=y,}\text{x?0}}$. It is a consequence of Brion and Vergne's formula which evaluates the sum . As in linear programming, f_c(y) can be obtained by inspection of the reduced-costs at the vertices of the polyhedron. We also provide an explicit result that relates f_c(ty) and the optimal value of the associated continous linear program, for large values of $\text{t∈}\text{N}$. To cite this article: J.B. Lasserre, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 863–866.     

Analyse d'un problème de tsunamiAnalysis of a tsunami problem

This article presents a model and a mathematical analysis of a tsunami problem due to the displacement of the lithosphere. We give some results showing the existence, smoothness and uniqueness of the solution. To cite this article: B. Di Martino et al., C. R. Acad. Sci. Paris, Ser. I 334 (2002) 551–556.     

Transfert lisse d'intégrales de KloostermanSmooth transfer of Kloosterman integrals

We establish the existence of smooth transfer between absolute Kloosterman integrals and Kloosterman integrals relative to a quadratic extension. To cite this article: H. Jacquet, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 229–232.     

Triplets spectraux en géométrie d'ArakelovSpectral triples in Arakelov geometry

In this Note, we use Connes' theory of spectral triples to provide a connection between Manin's model of the dual graph of the fiber at infinity of an Arakelov surface and the cohomology of the mapping cone of the local monodromy. To cite this article: C. Consani, M. Marcolli, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 779–784.     

Étude asymptotique locale de l'estimateur par ondelettesA law of the iterated logarithm for wavelet density estimator

We state a pointwise central limit theorem for the linear wavelet density estimator in a more general setting than the result of Wu [12]. Furthermore, we also give a pointwise law of the iterated logarithm for this density estimator. Our proof of the law of the iterated logarithm uses the results of Mason [9] on the asymptotic behavior of the tail empirical process. To cite this article: A. Massiani, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 553–556.     

Solutions entropiques des problèmes non locauxEntropy solutions of nonlocal problems

We introduce a notion of entropy solution for the nonlocal problem $\text{C}\text{f+f=ψ}$ on $\text{?Ω}$, where $\text{ψ∈}\text{L}{}^1\text{(?Ω)}$ and $\text{C}$ is a nonlinear capacity operator. We prove its existence and uniqueness. This notion of solution allows also to solve a general elliptic problem with nonlinear boundary conditions. To cite this article: K. Ammar, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 751–756.     

Chaı̂nes de Markov TripletTriplet Markov Chains

The Hidden Markov Chains (HMC) are widely applied in various problems. This succes is mainly due to the fact that the hidden process can be recovered even in the case of very large set of data. These models have been recetly generalized to ‘Pairwise Markov Chains’ (PMC) model, which admit the same processing power and a better modeling one. The aim of this note is to propose further generalization called Triplet Markov Chains (TMC), in which the distribution of the couple (hidden process, observed process) is the marginal distribution of a Markov chain. Similarly to HMC, we show that posterior marginals are still calculable in Triplets Markov Chains. We provide a necessary and sufficient condition that a TMC is a PMC, which shows that the new model is strictly more general. Furthermore, a link with the Dempster–Shafer fusion is specified. To cite this article: W. Pieczynski, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 275–278.     

Estimation d'une rupture en dépendance faibleChange point estimation for a weakly dependent sequence

Let $\text{(X}{}_{\mathrm{n}}\text{,Y}{}_{\mathrm{n}}\text{)}{}_{\mathrm{<mtext>n\in </mtext><mtext>N</mtext>}}$ be a stationary sequence governed by the model Y_n=m(X_n)+σ(X_n)ε_n where $\text{(ε}{}_{\mathrm{n}}\text{)}{}_{\mathrm{<mtext>n\in </mtext><mtext>N</mtext>}}$ is i.i.d. and independent from $\text{(X}{}_{\mathrm{n}}\text{)}{}_{\mathrm{<mtext>n\in </mtext><mtext>N</mtext>}}\text{.}$ The latter sequence satisfy a weak dependence condition proposed by Doukhan and Louhichi in [2]. We provide a Central Limit Theorem for jumps in the regression function. Our method deals with linear local regression described in [4]. We use a variation on Lindeberg–Rio method as in [5]. To cite this article: P. Ango Nze, C. Prieur, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 267–270.     

Calcul du label des gaps pour les quasi-cristauxComputation of the gap-labelling for quasi-crystals

We give in the present Note a proof of the Bellissard gap-labelling conjecture for quasi-crystals. Our main tools are the measured index theorem for laminations on the one hand, and the naturality of the longitudinal Chern character on the other hand. To cite this article: M.-T. Benameur, H. Oyono-Oyono, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 667–670.