Proving a conjecture of Dennis Johnson, we show that the Torelli subgroup Ig of the
genus g mapping class group has a finite generating set whose size grows cubically
with respect to g. Our main tool is a new space called the handle graph on which Ig
acts cocompactly.
Received: 24 June 2011
Revised: 11 August 2011
Accepted: 1 November 2011
Published: 2 January 2012
Proposed: Joan Birman
Seconded: Danny Calegari, Ronald Stern