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The paper concerns a -rigidity result for the characteristic foliations in symplectic geometry. A symplectic homeomorphism (in the sense of Eliashberg-Gromov) which preserves a smooth hypersurface also preserves its characteristic foliation.
We consider an n-dimensional compact Riemannian manifold (M,g) and show that the presence of a non-Killing conformal vector field ξ on M that is also an eigenvector of the Laplacian operator acting on smooth vector fields with eigenvalue λ > 0, together with an upper bound on the energy of the vector field ξ, implies that M is isometric to the n-sphere Sⁿ(λ). We also introduce the notion of φ-analytic conformal vector fields, study their properties, and obtain a characterization of n-spheres...
In this article, we prove new stability results for almost-Einstein hypersurfaces of the Euclidean space, based on previous eigenvalue pinching results. Then, we deduce some comparable results for almost umbilical hypersurfaces.
We study a problem of isometric compact 2-step nilmanifolds using some information on their geodesic flows, where is a simply connected 2-step nilpotent Lie group with a left invariant metric and is a cocompact discrete subgroup of isometries of . Among various works concerning this problem, we consider the algebraic aspect of it. In fact, isometry groups of simply connected Riemannian manifolds can be characterized in a purely algebraic way, namely by normalizers. So, suitable factorization...
We establish an integral geometric inequality on a closed Riemannian manifold with ∞-Bakry-Émery Ricci curvature bounded from below. We also obtain similar inequalities for Riemannian manifolds with totally geodesic boundary. In particular, our results generalize those of Wu (2014) for the ∞-Bakry-Émery Ricci curvature.
Nous donnons ici deux résultats sur le déterminant -régularisé d’un opérateur de Schrödinger sur une variété compacte . Nous construisons, pour , une suite où est un graphe fini qui se plonge dans via de telle manière que soit une triangulation de et où est un laplacien discret sur tel que pour tout potentiel sur , la suite de réels converge après renormalisation vers . Enfin, nous donnons sur toute variété riemannienne compacte de dimension inférieure ou égale à ...
We study representations of lattices of into . We show that if a representation is reductive and if is at least 2, then there exists a finite energy harmonic equivariant map from complex hyperbolic -space to complex hyperbolic -space. This allows us to give a differential geometric proof of rigidity results obtained by M. Burger and A. Iozzi. We also define a new invariant associated to representations into of non-uniform lattices in , and more generally of fundamental groups of orientable...
We introduce a notion of Hilbertian n-volume in metric spaces with Besicovitch-type inequalities built-in into the definitions. The present Part 1 of the article is, for the most part, dedicated to the reformulation of known results in our terms with proofs being reduced to (almost) pure tautologies. If there is any novelty in the paper, this is in forging certain terminology which, ultimately, may turn useful in an Alexandrov kind of approach to singular spaces with positive scalar curvature [Gromov...
Dans cet article nous nous intéressons aux immersions isométriques minimales (resp. pluriharmoniques) définies sur une variété riemannienne munie d’une 2-forme parallèle non triviale à valeurs dans une variété riemannienne ou kählérienne de courbure isotrope négative (resp. positive). Les résultats que nous obtenons généralisent certains résultats bien connus de non existence et de rigidité concernant les immersions minimales et pluriharmoniques de variétés kählériennes dans les espaces formes réels...
Dans cet article, on s’intéresse à l’aspect conforme du spectre d’opérateurs de Dirac dans le cadre des variétés à bord. Dans un premier temps, on étudie la première valeur propre de l’opérateur de Dirac sous la condition associée à un opérateur de chiralité conduisant à la définition d’un nouvel invariant spinoriel conforme. Dans la dernière partie, on s’intéresse à l’opérateur de Dirac du bord en reliant sa première valeur propre à des invariants reflétant la géométrie extrinsèque du bord. Dans...
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