On a question of Etnyre and Van Horn-Morris

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ISSN 1472-2739 (online)

ISSN 1472-2747 (print)

Algebraic & Geometric Topology 17 (2017) 561–566

DOI: 10.2140/agt.2017.17.561

The purpose of this note is to answer Question 6.12 of Etnyre and Van Horn-Morris [Monoids in the mapping class group, Geom. Topol. Monographs 19 (2015) 319–365], asking when the set of mapping classes whose fractional Dehn twist coefficient is greater than a given constant forms a monoid.

Fractional Dehn twist coefficient, monoid, mapping class group

Primary: 57M07

Secondary: 20F65

Received: 4 May 2016

Revised: 16 May 2016

Accepted: 6 June 2016

Published: 26 January 2017

Tetsuya Ito
Department of Mathematics Osaka University 1-1 Machikaneyama Toyonaka Osaka 560-0043 Japan
http://www.math.sci.osaka-u.ac.jp/~tetito/
Keiko Kawamuro
Department of Mathematics The University of Iowa 14 McLean Hall Iowa City, IA 52242 United States