Retraction of: Linear Representations of Hyperelliptic Mapping Class Groups

Abstract

Hyperelliptic mapping class groups are defined either as the centralizers of hyperelliptic involutions inside mapping class groups of oriented surfaces of finite type or as the inverse images of these centralizers by the natural epimorphisms between mapping class groups of surfaces with marked points. We study these groups in a systematic way. An application of this theory is a counterexample to the genus 2 case of a conjecture by Putman and Wieland on virtual linear representations of mapping class groups. In the last section, we study profinite completions of hyperelliptic mapping class groups: we extend the congruence subgroup property to the general class of hyperelliptic mapping class groups introduced above and then determine the centralizers of multitwists and of open subgroups in their profinite completions.

Notes on hyperelliptic mapping class groups

“…Since, for , the hyperelliptic mapping class group identifies with the mapping class group of the marked surface , in particular, we get a counterexample in genus to the conjecture by Putman and Wieland mentioned above. This fills a gap, pointed out to me by Aaron Landesman and Daniel Litt, in the proof of Theorem 3.13 in the, now-retracted, paper [13].…”

“…Acknowledgements. I thank Aaron Landesman and Daniel Litt for their comments on [13], which eventually led me to write this paper, and two anonymous referees for their comments on a previous version which contributed to improve it.…”