English

Monodromy groups of $\mathbb{C}\mathrm{P}^1$-structures on punctured surfaces

Geometric Topology 2021-09-17 v2 Complex Variables

Abstract

For a punctured surface SS, we characterize the representations of its fundamental group into PSL2(C)\mathrm{PSL}_2 (\mathbb{C}) that arise as the monodromy of a meromorphic projective structure on SS with poles of order at most two and no apparent singularities. This proves the analogue of a theorem of Gallo-Kapovich-Marden concerning CP1\mathbb{C}\mathrm{P}^1-structures on closed surfaces, and settles a long-standing question about characterizing monodromy groups for the Schwarzian equation on punctured spheres. The proof involves a geometric interpretation of the Fock-Goncharov coordinates of the moduli space of framed PSL2(C)\mathrm{PSL}_2 (\mathbb{C})-representations, following ideas of Thurston and some recent results of Allegretti-Bridgeland.

Keywords

Cite

@article{arxiv.1909.10771,
  title  = {Monodromy groups of $\mathbb{C}\mathrm{P}^1$-structures on punctured surfaces},
  author = {Subhojoy Gupta},
  journal= {arXiv preprint arXiv:1909.10771},
  year   = {2021}
}

Comments

27 pages, 5 figures. Final version, accepted for publication by the Journal of Topology

R2 v1 2026-06-23T11:24:01.298Z