On étudie les aspects locaux et globaux des actions holomorphes de SL() sur les variétés complexes de dimension trois, à partir de l’étude des algèbres de Lie de champs de vecteurs qui engendrent une action uniforme. On décrit géométriquement et dynamiquement une famille de telles algèbres étudiée par Halphen vers la fin du XIXème siècle. On donne des formes normales pour les actions de SL() au voisinage des orbites unidimensionnelles. On étudie ensuite les compactifications équivariantes des espaces...
We investigate the quadratic homogeneous holomorphic vector fields on that are semicomplete, this is, those whose solutions are single-valued in their maximal definition domain. To a generic quadratic vector field we rationally associate some complex numbers that turn out to be integers in the semicomplete case, thus showing that the linear equivalence classes of semicomplete vector fields are contained in some sort of lattice in the space of linear equivalence classes of quadratic ones. We prove...
We prove that a singular complex surface that admits a complete holomorphic vector field that has no invariant curve through a singular point of the surface is obtained from a Kato surface by contracting some divisor (in particular, it is compact). We also prove that, in a singular Stein surface endowed with a complete holomorphic vector field, a singular point of the surface where the zeros of the vector field do not accumulate is either a quasihomogeneous or a cyclic quotient singularity. We give...
We study germs of Lie algebras generated by two commuting vector fields in manifolds that are in the sense of Palais (those which do not present any evident obstruction to be the local model of an action of ). We study three particular pairs of homogeneous quadratic commuting vector fields (in , and ) and study the maximal Lie algebras generated by commuting vector fields whose 2-jets at the origin are the given homogeneous ones. In the first case we prove that the quadratic algebra is a smooth...
In this article we investigate the natural domain of definition of a holonomy map associated to a singular holomorphic foliation of the complex projective plane. We prove that germs of holonomy between algebraic curves can have large sets of singularities for the analytic continuation. In the Riccati context we provide examples with natural boundary and maximal sets of singularities. In the generic case we provide examples having at least a Cantor set of singularities and even a nonempty open set...
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