The Hilden subgroup of the braid group.
Stephen Tawn (University of Warwick)
Monday 27th April, 2009 16:00-17:00 Mathematics Building, room 204
The Hilden, or Wicket, subgroup of the braid group on 2n string can be defined in several ways. As the group of motions of n hoops in halfspace, as the stabiliser of n hoops under the action of the braid group on tangles, or as mapping class group. Using the mapping class point of view, we will construct a simply-connected complex with an action by the Hilden group. We will use this action to show that the Hilden group has a finite presentation.