Factorizable groups of homeomorphisms
A subsheaf of the sheaf of germs functions over an open subset of is called a sheaf of sub function. Comparing with the investigations of sheaves of ideals of , we study the finite presentability of certain sheaves of sub -rings. Especially we treat the sheaf defined by the distribution of Mather’s -classes of a mapping.
In our previous work we have defined the notion of characteristic classes of surface bundles, which are differentiable fibre bundles whose fibres are closed oriented surfaces. In this paper we derive new relations between these characteristic classes by considering a canonical embedding of a given surface bundle with cross section to its associated family of Jacobian manifolds. As a key technical step we determine the first cohomology group of the mapping class group of oriented surfaces with coefficients...
O’Grady showed that certain special sextics in called EPW sextics admit smooth double covers with a holomorphic symplectic structure. We propose another perspective on these symplectic manifolds, by showing that they can be constructed from the Hilbert schemes of conics on Fano fourfolds of degree ten. As applications, we construct families of Lagrangian surfaces in these symplectic fourfolds, and related integrable systems whose fibers are intermediate Jacobians.
Nous démontrons une condition suffisante pour qu’une feuille non captée d’un feuilletage de codimension 1 soit dense.Cette condition n’exige aucune hypothèse de compacité ; de plus elle est souvent nécessaire.Dans le cas particulier d’un feuilletage par des feuilles simplement connexes elle s’énonce ainsi : le sécant d’homotopie de contient un sous-semi-groupe abélien de rang 2.
Let be M a smooth manifold, A a local algebra and a manifold of infinitely near points on M of kind A. We build the canonical foliation on and we show that the canonical foliation on the tangent bundle TM is the foliation defined by its canonical field.
Nous classifions à homéomorphisme près les feuilletages de définis par l’équation où et sont des polynômes homogènes de même degré. Un tel feuilletage est soit trivial par plans, soit par plans et cylindres avec une ou deux composantes de Reeb, soit un feuilletage par plans dont l’espace des feuilles contient un ou deux ensembles de points non-séparés.