Displaying 21 – 40 of 75

Showing per page

Geometric subgroups of surface braid groups

Luis Paris, Dale Rolfsen (1999)

Annales de l'institut Fourier

Let M be a surface, let N be a subsurface, and let n m be two positive integers. The inclusion of N in M gives rise to a homomorphism from the braid group B n N with n strings on N to the braid group B m M with m strings on M . We first determine necessary and sufficient conditions that this homomorphism is injective, and we characterize the commensurator, the normalizer and the centralizer of π 1 N in π 1 M . Then we calculate the commensurator, the normalizer and the centralizer of B n N in B m M for large surface braid...

Géométries modèles de dimension trois

Yves de Cornulier (2008/2009)

Séminaire de théorie spectrale et géométrie

On expose une preuve détaillée de la classification par Thurston des huit géométries modèles de dimension trois.

Involutions of 3-dimensional handlebodies

Andrea Pantaleoni, Riccardo Piergallini (2011)

Fundamenta Mathematicae

We study the orientation preserving involutions of the orientable 3-dimensional handlebody H g , for any genus g. A complete classification of such involutions is given in terms of their fixed points.

Mapping class group of a handlebody

Bronisław Wajnryb (1998)

Fundamenta Mathematicae

Let B be a 3-dimensional handlebody of genus g. Let ℳ be the group of the isotopy classes of orientation preserving homeomorphisms of B. We construct a 2-dimensional simplicial complex X, connected and simply-connected, on which ℳ acts by simplicial transformations and has only a finite number of orbits. From this action we derive an explicit finite presentation of ℳ.

Maximal actions of finite 2-groups on ℤ₂-homology 3-spheres

Mattia Mecchia (2004)

Fundamenta Mathematicae

It is known that a finite 2-group acting on a ℤ₂-homology 3-sphere has at most ten conjugacy classes of involutions; the action of groups with the maximal number of conjugacy classes of involutions is strictly related to some questions concerning the representation of hyperbolic 3-manifolds as 2-fold branched coverings of knots. Using a low-dimensional approach we classify these maximal actions both from an algebraic and from a geometrical point of view.

Currently displaying 21 – 40 of 75