The geometry of two generator groups: Hyperelliptic handlebodies

Jane Gilman, Linda Keen

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


A Kleinian group naturally stabilizes certain subdomains and closed subsets of the closure of hyperbolic three space and yields a number of different quotient surfaces and manifolds. Some of these quotients have conformal structures and others hyperbolic structures. For two generator free Fuchsian groups, the quotient three manifold is a genus two solid handlebody and its boundary is a hyperelliptic Riemann surface. The convex core is also a hyperelliptic Riemann surface. We find the Weierstrass points of both of these surfaces. We then generalize the notion of a hyperelliptic Riemann surface to a 'hyperelliptic' three manifold. We show that the handlebody has a unique order two isometry fixing six unique geodesic line segments, which we call the Weierstrass lines of the handlebody. The Weierstrass lines are, of course, the analogue of the Weierstrass points on the boundary surface. Further, we show that the manifold is foliated by surfaces equidistant from the convex core, each fixed by the isometry of order two. The restriction of this involution to the equidistant surface fixes six generalized Weierstrass points on the surface. In addition, on each of these equidistant surfaces we find an orientation reversing involution that fixes curves through the generalized Weierstrass points.

Original languageEnglish (US)
Pages (from-to)159-190
Number of pages32
JournalGeometriae Dedicata
Issue number1
StatePublished - Feb 2005

All Science Journal Classification (ASJC) codes

  • Geometry and Topology


  • Fuchsian groups
  • Hyper elliptic surfaces
  • Kleinian groups
  • Riemann surfaces
  • Schottky groups


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