Liftable mapping class groups of certain branched covers of torus
Abstract
Let be a closed oriented hyperbolic surface of genus with marked points, with the understanding that . Let be the mapping class group of and be the liftable mapping class group associated to a cover . For the cover , Ghaswala, in his PhD thesis, derived a finite presentation for when and a finite generating set when using the Reidemeister-Schreier rewriting process. In this paper, we derive a finite generating set for for all . In the process, we also prove that the kernel of the homology representation is normally generated by a Dehn twist about a separating simple closed curve, and it is free with a countable basis. We also provide an explicit countable basis for consisting of separating Dehn twists. As an application of Birman-Hilden theory, we provide a finite generating set for the normalizer of the Deck group of in when . We conclude the paper by proving that is maximal in if and only if is prime.
Cite
@article{arxiv.2509.11788,
title = {Liftable mapping class groups of certain branched covers of torus},
author = {Pankaj Kapari},
journal= {arXiv preprint arXiv:2509.11788},
year = {2025}
}
Comments
Fixed some typos. 12 pages, 3 figures. Comments are welcome