Geometrization of 3-dimensional orbifolds, Part I: Geometry of cone manifolds
This paper has been withdrawn, because its material has been revised and became part of paper math.GT/0010184
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arXiv subjects
Bernhard Leeb
Publications and source records attributed to Bernhard Leeb.
Geometrization of 3-dimensional orbifolds
The purpose of this article is to give a proof of the Orbifold Theorem announced by Thurston in late 1981: If $O$ is a compact, connected, orientable, irreducible and topologically atoroidal 3-orbifold with non-empty ramification locus, then $O$ is geometric. As a corollary, any smooth orientation preserving non-free finite group action on $S^3$ is conjugate to an orthogonal action.
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The generalized triangle inequalities for rank 3 symmetric spaces of noncompact type
We compute the generalized triangle inequalities explicitly for all rank 3 symmetric spaces. We find that for Sp(6) the corresponding polyhedral cone has 102 facets and 51 edges.
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A Geometric Characteristic Splitting in all Dimensions
We prove the existence of a geometric characteristic submanifold for non-positively curved manifolds of any dimension greater than or equal to three. In dimension three, our result is a geometric version of the topological characteristic submanifold theorem due to Jaco, Shalen and Johannson.
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Groups quasi-isometric to symmetric spaces
We determine the structure of finitely generated groups which are quasi-isometric to symmetric spaces of noncompact type, allowing Euclidean de Rham factors If $X$ is a symmetric space of noncompact type with no Euclidean de Rham factor, and $\Ga$ is a finitely generated group quasi-isometric to the product $\E^k\times X$, then there is an exact sequence $1\ra H\ra\Ga\ra L\ra 1$ where $H$ contains a finite index copy of $\Z^k$ and $L$ is a uniform lattice in the isometry group of $X$.
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3-manifolds with(out) metrics of nonpositive curvature
In the context of Thurstons geometrisation program we address the question which compact aspherical 3-manifolds admit Riemannian metrics of nonpositive curvature. We show that non-geometric Haken manifolds generically, but not always, admit such metrics. More precisely, we prove that a Haken manifold with, possibly empty, boundary of zero Euler characteristic admits metrics of nonpositive curvature if the boundary is non-empty or if at least one atoroidal component occurs in its canonical topological decomposition. Our arguments are based on Thurstons Hyperbolisation Theorem. We give examples of closed graph-manifolds with linear gluing graph and arbitrarily many Seifert components which do not admit metrics of nonpositive curvature.
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