Exponential mapping for Lie groupoids
There is a well-known procedure -induction- for extending an action of a subgroup H of a Lie group G on a topological space X to an action of G on an associated space. Induction can also extend a smooth action of a subgroup H of a Lie group G on a manifold M to a smooth action of G on an associated manifold. In this paper elementary methods are used to show that induction also works in the category of (nonsingular) real algebraic varieties and regular or entire maps if G is a compact abelian Lie...
Let be a complex manifold, a generic submanifold of , the real underlying manifold to . Let be an open subset of with analytic, a complexification of . We first recall the notion of -tuboid of and of and then give a relation between; we then give the corresponding result in terms of microfunctions at the boundary. We relate the regularity at the boundary for to the extendability of functions on to -tuboids of . Next, if has complex dimension 2, we give results on extension...
Let M be a separable Finsler manifold of infinite dimension. Then it is proved, amongst other results, that under suitable conditions of local extensibility the germ of a function, or of a section of a vector bundle, on the union of a closed submanifold and a closed locally compact set in M, extends to a function on the whole of M.
On s’intéresse au problème de savoir quelle est la rigidité apportée au spectre d’une variété riemannienne compacte par le fait de fixer son volume et se classe conforme, et en particulier de déterminer si on peut faire tendre les valeurs propres vers 0 ou l’infini sous cette contrainte. On considère successivement les cas du laplacien usuel agissant sur les fonctions, l’opérateur de Dirac, le laplacien conforme et le laplacien de Hodge-de Rham.
We prove the existence of extremal domains with small prescribed volume for the first eigenvalue of Laplace-Beltrami operator in some Riemannian manifold. These domains are close to geodesic spheres of small radius centered at a nondegenerate critical point of the scalar curvature.
We establish the sharp lower bound for eigenvalues of a metric graph.