Past Junior Topology and Group Theory Seminar

23 November 2011
16:00
David Hume
Abstract

We present recent results of Dani Wise which tie together many of the themes of this term's jGGT meetings: hyperbolic and relatively hyperbolic groups, (in particular limit groups), graphs of spaces, 3-manifolds and right-angled Artin groups.
Following this, we make an attempt at explaining some of the methods, beginning with special non-positively curved cube complexes.

  • Junior Topology and Group Theory Seminar
22 June 2011
16:00
Abstract
In euclidean space there is a well-known parallelogram law relating the length of vectors a, b, a+b and a-b. In the talk I give a similar formula for translation lengths of isometries of CAT(0)-spaces. Given an action of the automorphism group of a free product on a CAT(0)-space, I show that certain elements can only act by zero translation length. In comparison to other well-known actions this leads to restrictions about homomorphisms of these groups to other groups, e.g. mapping class groups.
  • Junior Topology and Group Theory Seminar

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