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1.
M. A. Rieffel [24] a introduit le rang stable topologique (tsr),pour généraliser aux C*-algèbres, le conceptde dimension de recouvrement pour les espaces compacts, affirmantainsi le principe selon lequel une C*-algèbre est unespace localement compact non commutatif. II a montréque l'on a tsr ((A)) = [dim (Â)] + 1, pour toute C*-algèbre commutative A etque trs (B/J) tsr (B), pour toute C*-algèbre B et pourtout idéal bilatère fermé J dans B (généralisantle fait que, si X est un espace compact et F un sous-ensemblefermé dans X, alors on a dim (F) dim (X), oùdim(X) est la dimension de recouvrement de X [19]). D'autrepart, le rang stable topologique peut être utilisépour obtenir des théorèmes de cancellationpour les modules projectifs, comme ceci est fait dans [25, 2].Un peu plus tard, R. H. Herman et L. N. Vaserstein [14] ontmontré que pour toute C*-algèbre unitaire A, lerang stable topologique de A et le rang stable de Basse de Acoincident, done, pour toute C*-algèbre unitaire A, onnote sr(A) cette valeur commune appelée rang stable deA. Les C*-algèbres unitaires de rang stable 1 ont étéétudiée géométriquement par M. Rørdam[27], il a montré que l'on a sr(A) = 1 si et seulementsi l'enveloppe convexe des unitaires de A est égale àla boule unité fermé de A. D'autre part, Rieffel[24] avait introduit le rang stable connexe (csr) d'une C*-algèbre,sur lequel V. Nistor [18] a publié un article trésintéressant. Mon travail dans ce papier consiste àcompléter certains travaux déjà entreprisdans les articles qui sont cités ci-dessus. 相似文献
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Zbigniew Lonc 《Order》1994,11(2):149-158
We show that in an ordered setP of width 3 there always exists a fibre (i.e., a subset intersecting each maximal nontrivial antichain) of size at most 11/18|P|. This improves previously known results.Research supported by Polish KBN Grant 2 2037 92 03. 相似文献
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This paper is concerned with extending the theory of Everstine& Pipkin (1973) for elastic materials reinforced by inextensiblefibres to allow for slight fibre-extensibility. Small deformationsonly are considered. The stress-strain relation for a materialreinforced by two distinct families of extensible fibres isderived and compared with the similar equation for inextensiblefibres to deduce the effect on the elastic constants of approachingthe limit of fibre-inextensibility. It is then shown by twosimple examples how some problems which are indeterminate iffibre inextensibility is assumed b initio are solvable if fibreextensibility is assumed first and the limit of fibre-inextensibilityapproached in the solution. Finally the phenomenon of singularsheets of fibres carrying infinite stress predicted by the inextensibletheory in many cases is examined in a particular problem bya boundary layer technique. 相似文献
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Infinite families of curves are constructed of genus 2 and 3over Q whose jacobians have high rank over Q. More precisely,if E is an elliptic curve with rank at least r over Q, an infinitefamily of curves are constructed of genus 2 whose jacobianshave rank at least r+4 over Q, and, under certain conditions,an infinite family of curves are constructed of genus 3 whosejacobians have rank at least 2r over Q. On specialisation, afamily of curves are obtained of genus 2 whose jacobians haverank at least 27 and a family of curves are obtained of genus3 whose jacobians have rank at least 26; one of these has rankat least 42. 相似文献
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Alain Pajor 《Israel Journal of Mathematics》1987,57(1):101-106
The Banach spaces for which all finite dimensional quotient spaces have uniformly bounded volume ratio are characterized by
a weak type 2 property. This is the dual form of a recently published result of V. Milman and G. Pisier on weak cotype 2 Banach
spaces.
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Pascal Honvault 《Mathematische Zeitschrift》1997,225(2):295-316
Sans résumé
Received 25 April 1994; in final form 27 June 1995 相似文献
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Jean -Paul Thouvenot 《Probability Theory and Related Fields》1972,24(2):135-137
Résumé On démontre la convergence en moyenne de 1'information (théoréme de Mac-Millan) pour 1'action de Z2. 相似文献
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Dans cet article, nous nous intéressons aux problèmesde structure galoisienne associés aux couples (E/L, a),où E désigne une courbe elliptique définiesur le corps de nombres L et a un endomorphisme de E. Si E està multiplication complexe, nous notons k le corps quadratiqueimaginaire dont l'anneau des entiers décrit End(E) etL une extension de k. Ainsi a est-il selon les cas un entieralgébrique de k ou un élément de Z. 相似文献
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Nicolas Dutertre 《Geometriae Dedicata》2004,105(1):43-59
We establish a Gauss—Bonnet type formula for a smooth fibre of a nonproper real polynomial of
n
. For this we need to study topological properties of a generic hyperplane section of this fibre. 相似文献
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We present a calculation to determine the radiation losses forarbitrarily bent, weakly guiding optical fibres. Our resultsare derived for the full set of vector Maxwell's equations,and show that the rate of energy loss due to radiation differsfor the various modes. These results are different from thatcalculated from a scalar theory, where the so-called linearlypolarized (LP) modes are used to approximate the electromagneticfield distributions, showing that in this case scalar theoriesgive incorrect loss rates. We also show that different rangesfor the size of the curvature and torsion produce quite differenteffects. In particular, we show that, for smaller amounts ofcurvature and torsion, the modes retain the basic structureof the modes in the straight fibre while losing energy slowlyat differing rates, while, for larger amounts of curvature andtorsion, the modes become distorted by the bending. 相似文献
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Matthieu Gendulphe 《Mathematische Annalen》2011,350(4):919-951
We introduce a new tool, the contiguity graph, which enables us to determine the Bers’s constant in genus two. 相似文献
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Giovanni Masala 《Rendiconti del Circolo Matematico di Palermo》1996,45(3):351-376
La classe di congruenza di una terna {A, B, C} inG 2(? n ), sotto l’azione del gruppo ortogonale 0(n, ?), dipende da 9 parametri al più. Possiamo associare in modo naturale a questa terna, una terna di proiettori ortogonali {P A ,P B ,P C }. Utilizzando la teoria algebrica degli invarianti, viene dato un sistema completo di invarianti ortogonali composto da tracce di opportune combinazioni diP A ,P B , eP C che consentono di determinare in modo unico la classe di congruenza della terna di partenza. 相似文献
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Yves Laszlo 《Mathematische Annalen》1994,299(1):597-608
Sans résumé
Partiellement financé par le contrat Science Geometry of Algebraic Varieties, contrat no SCI-0398-C 相似文献