Sections Boréliennes pour les feuilletages mesurés.
We introduce topological 𝒬-holonomy groupoids for singular foliations (M,ℱ) with an Ehresmann connection 𝒬 using 𝒬-holonomy groups, which have a global character. We show advantage of our groupoids over known ones.
Compact, -foliated manifolds of codimension one, having all leaves proper, are shown to be -smoothable. More precisely, such a foliated manifold is homeomorphic to one of class . The corresponding statement is false for foliations with nonproper leaves. In that case, there are topological distinctions between smoothness of class and of class for every nonnegative integer .
Families of codimension-one foliations and laminations are constructed in certain 3-manifolds, with the property that their transverse intersection with the boundary torus of the manifold consists of parallel curves whose slope varies continuously with certain parameters in the construction. The 3-manifolds are 2-bridge knot complements and punctured-torus bundles.
The KV-homology theory is a new framework which yields interesting properties of lagrangian foliations. This short note is devoted to relationships between the KV-homology and the KV-cohomology of a lagrangian foliation. Let us denote by (resp. ) the KV-algebra (resp. the space of basic functions) of a lagrangian foliation F. We show that there exists a pairing of cohomology and homology to . That is to say, there is a bilinear map , which is invariant under F-preserving symplectic diffeomorphisms....
The first part of this paper is concerned with geometrical and cohomological properties of Lie flows on compact manifolds. Relations between these properties and the Euler class of the flow are given.The second part deals with 3-codimensional Lie flows. Using the classification of 3-dimensional Lie algebras we give cohomological obstructions for a compact manifold admits a Lie flow transversely modeled on a given Lie algebra.
Soit la -algèbre, ou bien réduite ou bien maximale, associée à la variété feuilletée , et la -algèbre élémentaire des opérateurs compacts. Alors, si dim, on montre que est isomorphe à .
We show that the singular holomorphic foliations induced by dominant quasi-homogeneous rational maps fill out irreducible components of the space of singular foliations of codimension and degree on the complex projective space , when . We study the geometry of these irreducible components. In particular we prove that they are all rational varieties and we compute their projective degrees in several cases.
Un feuilletage de codimension un sur une variété orientable est de Rolle s’il vérifie la propriété suivante : une courbe transverse à coupe au plus une fois chaque feuille. Soit une fonction tapissante sur , i.e. propre et possédant un nombre fini de valeurs critiques. Nous montrons que si l’ensemble des singularités de la restriction de aux feuilles de vérifie certaines propriétés de finitude, alors la restriction de au complémentaire d’un nombre fini de feuilles possède une structure...