Addendum to: Commensurations of the Johnson kernel
Geometric Topology
2014-11-11 v1 Group Theory
Abstract
Let K(S) be the subgroup of the extended mapping class group, Mod(S), generated by Dehn twists about separating curves. In our earlier paper, we showed that Comm(K(S)) and Aut(K(S)) are both isomorphic to Mod(S) when S is a closed, connected, orientable surface of genus g at least 4. By modifying our original proof, we show that the same result holds for g at leat 3, thus confirming Farb's conjecture in all cases (the statement is not true for any g less than 3).
Cite
@article{arxiv.0710.3089,
title = {Addendum to: Commensurations of the Johnson kernel},
author = {Tara E. Brendle and Dan Margalit},
journal= {arXiv preprint arXiv:0710.3089},
year = {2014}
}
Comments
4 pages, 2 figures; to appear in Geometry and Topology