We investigate the natural domain of definition of the Godbillon-Vey 2- dimensional cohomology class of the group of diffeomorphisms of the circle. We introduce the notion of area functionals on a space of functions on the circle, we give a sufficiently large space of functions with nontrivial area functional and we give a sufficiently large group of Lipschitz homeomorphisms of the circle where the Godbillon-Vey class is defined.
We define the concept of a bi-Legendrian connection associated to a bi-Legendrian structure on an almost -manifold . Among other things, we compute the torsion of this connection and prove that the curvature vanishes along the leaves of the bi-Legendrian structure. Moreover, we prove that if the bi-Legendrian connection is flat, then the bi-Legendrian structure is locally equivalent to the standard structure on .
Laminations are classic sets of disjoint and non-self-crossing curves on surfaces. Lamination languages are languages of two-way infinite words which code laminations by using associated labeled embedded graphs, and which are subshifts. Here, we characterize the possible exact affine factor complexities of these languages through bouquets of circles, i.e. graphs made of one vertex, as representative coding graphs. We also show how to build families of laminations together with corresponding lamination...
This paper is devoted to define a characteristic homomorphism for a subfoliation and to study its relation with the usual characteristic homomorphism for each foliation (as defined by Bott). Moreover, two applications are given: 1) the Yamato’s 2-codimensional foliation is shown to be no homotopic to in a (1,2)-codimensional subfoliation; 2) an obstruction to the existence of everywhere independent and transverse infinitesimal transformations of a foliation is obtained, when and these...
In this paper a construction of characteristic classes for a subfoliation is given by using Kamber-Tondeur’s techniques. For this purpose, the notion of -foliated principal bundle, and the definition of its associated characteristic homomorphism, are introduced. The relation with the characteristic homomorphism of -foliated bundles, , the results of Kamber-Tondeur on the cohomology of --algebras. Finally, Goldman’s results on the restriction of foliated bundles to the leaves of a foliation...
Le but de ce travail est double : d’une part, généraliser la construction des classes exotiques pour l’appliquer à d’autres problèmes géométriques que ceux issus des -structures ; d’autre part, préciser, grâce à la notion de -connexité, remplaçant avantageusement les formules de dérivation utilisées précédemment, l’argument d’invariance homotopique permettant d’obtenir des théorèmes de rigidité, montrant simultanément pourquoi la seule connexité des ensembles de connexions considérés ne suffit...
On établit la classification topologique des feuilletages holomorphes de codimension 1 singuliers à l’origine de , admettant une intégrale première multiforme du type .