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Caustics and wave front propagations: applications to differential geometry

Shyuichi Izumiya, Masatomo Takahashi (2008)

Banach Center Publications

This is mainly a survey on the theory of caustics and wave front propagations with applications to differential geometry of hypersurfaces in Euclidean space. We give a brief review of the general theory of caustics and wave front propagations, which are well-known now. We also consider a relationship between caustics and wave front propagations which might be new. Moreover, we apply this theory to differential geometry of hypersurfaces, getting new geometric properties.

Cayley's problem

Peter Petek (1990)

Aplikace matematiky

Newton's method for computation of a square root yields a difference equation which can be solved using the hyperbolic cotangent function. For the computation of the third root Newton's sequence presents a harder problem, which already Cayley was trying to solve. In the present paper two mutually inverse functions are defined in order to solve the difference equation, instead of the hyperbolic cotangent and its inverse. Several coefficients in the expansion around the fixed points are obtained,...

Cells of harmonicity

Kolář, Martin (1991)

Proceedings of the Winter School "Geometry and Physics"

[For the entire collection see Zbl 0742.00067.]We are interested in partial differential equations on domains in 𝒞 n . One of the most natural questions is that of analytic continuation of solutions and domains of holomorphy. Our aim is to describe the domains of holomorphy for solutions of the complex Laplace and Dirac equations. We call them cells of harmonicity. We deduce their properties mostly by examining geometrical properties of the characteristic surface (which is the same for both equations),...

Central extensions of infinite-dimensional Lie groups

Karl-Hermann Neeb (2002)

Annales de l’institut Fourier

The main result of the present paper is an exact sequence which describes the group of central extensions of a connected infinite-dimensional Lie group G by an abelian group Z whose identity component is a quotient of a vector space by a discrete subgroup. A major point of this result is that it is not restricted to smoothly paracompact groups and hence applies in particular to all Banach- and Fréchet-Lie groups. The exact sequence encodes in particular precise obstructions for a given Lie algebra...

Champs de vecteurs et formes différentielles sur une variété des points proches

Basile Guy Richard Bossoto, Eugène Okassa (2008)

Archivum Mathematicum

Let M be a smooth manifold, A a local algebra in sense of André Weil, M A the manifold of near points on M of kind A and 𝔛 ( M A ) the module of vector fields on M A . We give a new definition of vector fields on M A and we show that 𝔛 ( M A ) is a Lie algebra over A . We study the cohomology of A -differential forms. Résumé. On considère M une variété différentielle, A une algèbre locale au sens d’André Weil, M A la variété des points proches de M d’espèce A et 𝔛 ( M A ) le module des champs de vecteurs sur M A . On donne une nouvelle...

Champs magnétiques et inégalités de Morse pour la d ' ' -cohomologie

Jean-Pierre Demailly (1985)

Annales de l'institut Fourier

Nous démontrons des inégalités de Morse-Witten asymptotiques pour la dimension des groupes de cohomologie des puissances tensorielles d’un fibré holomorphe en droites hermitien au-dessus d’une variété C - analytique compacte. La dimension du q -ième groupe de cohomologie se trouve ainsi majorée par une intégrale de courbure intrinsèque, étendue à l’ensemble des points d’indice q de la forme de courbure du fibré. La preuve repose sur un théorème spectral qui décrit la distribution asymptotique des...

Champs totalement radiaux sur une structure de Thom-Mather

Stéphane Simon (1995)

Annales de l'institut Fourier

Dans la première partie de ce travail, on prouve l’existence de champs stratifiés dits totalement radiaux sur un ensemble stratifié abstrait (e.s.a.). Ces champs sont stables et peuvent être choisis continus sur les espaces stratifiés plongés qui sont ( C ) -réguliers au sens de K. Bekka. Dans la seconde partie, on établit pour ces espaces un théorème de Poincaré-Hopf pour les champs totalement radiaux continus. On en déduit un résultat similaire pour les e.s.a.

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