Subgroups of profinite surface groups
Group Theory
2010-11-08 v1
Abstract
We study the subgroup structure of the \'etale fundamental group of a projective curve over an algebraically closed field of characteristic 0. We obtain an analog of the diamond theorem for . As a consequence we show that most normal subgroups of infinite index are semi-free. In particular every proper open subgroup of a normal subgroup of infinite index is semi-free.
Cite
@article{arxiv.1011.1419,
title = {Subgroups of profinite surface groups},
author = {Lior Bary-Soroker and Katherine F. Stevenson and Pavel Zalesskii},
journal= {arXiv preprint arXiv:1011.1419},
year = {2010}
}