English

Generating the liftable mapping class groups of cyclic covers of spheres

Geometric Topology 2025-09-24 v2

Abstract

For g2g\geq 2, let Mod(Sg)\mathrm{Mod}(S_g) be the mapping class group of closed orientable surface SgS_g of genus gg. In this paper, we derive a finite generating set for the liftable mapping class groups corresponding to finite-sheeted regular branched cyclic covers of spheres. As an application, we provide an algorithm to derive presentations of these liftable mapping class groups, and the normalizers and centralizers of periodic mapping classes corresponding to these covers. Furthermore, we determine the isomorphism classes of the normalizers of irreducible periodic mapping classes in Mod(Sg)\mathrm{Mod}(S_g). Moreover, we derive presentations for the liftable mapping class groups corresponding to covers induced by certain reducible periodic mapping classes. Consequently, we derive a presentation for the centralizer and normalizer of a reducible periodic mapping class in Mod(Sg)\mathrm{Mod}(S_g) of the highest order 2g+22g+2. As final applications of our results, we recover the generating sets of the liftable mapping class groups of the hyperelliptic cover obtained by Birman-Hilden and the balanced superelliptic cover obtained by Ghaswala-Winarski.

Keywords

Cite

@article{arxiv.2308.12071,
  title  = {Generating the liftable mapping class groups of cyclic covers of spheres},
  author = {Pankaj Kapari and Kashyap Rajeevsarathy and Apeksha Sanghi},
  journal= {arXiv preprint arXiv:2308.12071},
  year   = {2025}
}

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