English

Cyclic-Schottky strata of Schottky space

Geometric Topology 2026-05-07 v1

Abstract

Schottky space Sg{\mathcal S}_{g}, where g2g \geq 2 is an integer, is a connected complex orbifold of dimension 3(g1)3(g-1); it provides a parametrization of the PSL2(C){\rm PSL}_{2}({\mathbb C})-conjugacy classes of Schottky groups Γ\Gamma of rank gg. The branch locus BgSg{\mathcal B}_{g} \subset {\mathcal S}_{g}, consisting of those conjugacy classes of Schottky groups being a finite index proper normal subgroup of some Kleinian group, is known to be connected. If [Γ]Bg[\Gamma] \in {\mathcal B}_{g}, then there is a Kleinian group KK containing Γ\Gamma as a normal subgroup of index some prime integer p2p \geq 2. The structural description, in terms of Klein-Maskit Combination Theorems, of such a group KK is completely determined by a triple (t,r,s)(t,r,s), where t,r,s0t,r,s \geq 0 are integers such that g=p(t+r+s1)+1rg=p(t+r+s-1)+1-r. For each such a tuple (g,p;t,r,s)(g,p;t,r,s) there is a corresponding cyclic-Schottky stratum F(g,p;t,r,s)BgF(g,p;t,r,s) \subset {\mathcal B}_{g}. It is known that F(g,2;t,r,s)F(g,2;t,r,s) is connected.In this paper, for p3p \geq 3, we study the connectivity of these F(g,p;t,r,s)F(g,p;t,r,s).

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Cite

@article{arxiv.2605.04205,
  title  = {Cyclic-Schottky strata of Schottky space},
  author = {Ruben A. Hidalgo and Milagros Izquierdo},
  journal= {arXiv preprint arXiv:2605.04205},
  year   = {2026}
}