Geometrization of 3-dimensional orbifolds

  title={Geometrization of 3-dimensional orbifolds},
  author={Michel Boileau and Bernhard Leeb and Joan Porti},
  journal={Annals of Mathematics},
This paper is devoted to the proof of the orbifold theorem: If O is a compact connected orientable irreducible and topologically atoroidal 3-orbifold with nonempty ramification locus, then O is geometric (i.e. has a metric of constant curvature or is Seifert fibred). As a corollary, any smooth orientationpreserving nonfree finite group action on S3 is conjugate to an orthogonal action. 

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