English

Generating the liftable mapping class groups of regular cyclic covers

Geometric Topology 2025-04-30 v3 Group Theory

Abstract

Let Mod(Sg)\mathrm{Mod}(S_g) be the mapping class group of the closed orientable surface of genus g1g \geq 1, and let LModp(X)\mathrm{LMod}_{p}(X) be the liftable mapping class group associated with a finite-sheeted branched cover p:SXp:S \to X, where XX is a hyperbolic surface. For k2k \geq 2, let pk:Sk(g1)+1Sgp_k: S_{k(g-1)+1} \to S_g be the standard kk-sheeted regular cyclic cover. In this paper, we show that {LModpk(Sg)}k2\{\mathrm{LMod}_{p_k}(S_g)\}_{k \geq 2} forms an infinite family of self-normalizing subgroups in Mod(Sg)\mathrm{Mod}(S_g), which are also maximal when kk is prime. Furthermore, we derive explicit finite generating sets for LModpk(Sg)\mathrm{LMod}_{p_k}(S_g) for g3g \geq 3 and k2k \geq 2, and LModp2(S2)\mathrm{LMod}_{p_2}(S_2). For g2g \geq 2, as an application of our main result, we also derive a generating set for LModp2(Sg)CMod(Sg)(ι)\mathrm{LMod}_{p_2}(S_g) \cap C_{\mathrm{Mod}(S_g)}(\iota), where CMod(Sg)(ι)C_{\mathrm{Mod}(S_g)}(\iota) is the centralizer of the hyperelliptic involution ιMod(Sg)\iota \in \mathrm{Mod}(S_g). Let L\mathcal{L} be the infinite ladder surface, and let qg:LSgq_g : \mathcal{L} \to S_g be the standard infinite-sheeted cover induced by hg1\langle h^{g-1} \rangle where hh is the standard handle shift on L\mathcal{L}. As a final application, we derive a finite generating set for LModqg(Sg)\mathrm{LMod}_{q_g}(S_g) for g3g \geq 3.

Keywords

Cite

@article{arxiv.2111.01626,
  title  = {Generating the liftable mapping class groups of regular cyclic covers},
  author = {Soumya Dey and Neeraj K. Dhanwani and Harsh Patil and Kashyap Rajeevsarathy},
  journal= {arXiv preprint arXiv:2111.01626},
  year   = {2025}
}

Comments

16 pages, 9 figures. Incorporated changes suggested by referee. To appear in Math. Proc. Cambridge Philos. Soc

R2 v1 2026-06-24T07:22:43.139Z