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Unpublished Paper
Quasi-platonic PSL2(q)-actions on closed Riemann surfaces
Mathematical Sciences Technical Reports (MSTR) (2015)
  • Sean A Broughton, Rose-Hulman Institute of Technology

This paper is the first of two papers whose combined goal is to explore the dessins d'enfant and symmetries of quasi-platonic actions of PSL2(q). A quasi-platonic action of a group G on a closed Riemann S surface is a conformal action for which S/G is a sphere and S->S/G is branched over {0, 1,infinity}. The unit interval in S/G may be lifted to a dessin d'enfant D, an embedded bipartite graph in S. The dessin forms the edges and vertices of a tiling on S by dihedrally symmetric polygons, generalizing the idea of a platonic solid. Each automorphism p in the absolute Galois group determines a transform Sp by transforming the coefficients of the defining equations of S. The transform defines a possibly new quasi-platonic action and a transformed dessin Dp. Here, in this paper, we describe the quasi-platonic actions of PSL2(q) and the action of the absolute Galois group on PSL2(q) actions. The second paper discusses the quasi-platonic actions constructed from symmetries (reflections) and the resulting triangular tiling that refines the dessin d'enfant. In particular, the number of ovals and the separation properties of the mirrors of a symmetry are determined.

  • Riemann surface,
  • quasi-platonic surface,
  • automorphism group,
  • symmetries. 2
Publication Date
December 2, 2015

MSTR 15-01

Citation Information
Sean A Broughton. "Quasi-platonic PSL2(q)-actions on closed Riemann surfaces" Mathematical Sciences Technical Reports (MSTR) (2015)
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