Existence results for embedded minimal surfaces of controlled topological type, I
This paper is devoted to the existence of conformal metrics on with prescribed scalar curvature. We extend well known existence criteria due to Bahri-Coron.
We introduce Quantum Inner State manifolds (QIS manifolds) as (compact) -dimensional symplectic manifolds endowed with a -tamed almost complex structure and with a nowhere vanishing and normalized section of the bundle satisfying the condition .We study the moduli space of QIS deformations of a given Calabi-Yau manifold, computing its tangent space and showing that is non obstructed. Finally, we present several examples of QIS manifolds.
A homogeneous Riemannian manifold is called a “g.o. space” if every geodesic on arises as an orbit of a one-parameter subgroup of . Let be such a “g.o. space”, and an -invariant vector subspace of such that . A geodesic graph is a map such that is a geodesic for every . The author calculates explicitly such geodesic graphs for certain special 2-step nilpotent Lie groups. More precisely, he deals with “generalized Heisenberg groups” (also known as “H-type groups”) whose center has...
L’analyse de l’article de Poincaré sur les géodésiques fait apparaître qu’il entretient des liens complexes avec les travaux antérieurs de Poincaré en mécanique céleste. Nous montrerons que le problème des géodésiques des surfaces convexes est traité comme un paradigme grâce auquel Poincaré explicite une méthode qui n’était présentée qu’à l’état d’ébauche dans ses ouvrages de mécanique céleste. Cette étude de cas permet ainsi de mettre en évidence l’utilisation par Poincaré d’une technique d’écriture...
We extend a remarkable theorem of Derdziński and Shen, on the restrictions imposed on the Riemann tensor by the existence of a nontrivial Codazzi tensor. We show that the Codazzi equation can be replaced by a more general algebraic condition. The resulting extension applies both to the Riemann tensor and to generalized curvature tensors.