Infinite Groups Seminar: Ramagge, Thomas

The next Infinite Groups Seminar will be this Wednesday 11 May at the University of
Wollongong.  The schedule, titles and abstracts are below.  

The first talk by Jacqui Ramagge will be broadcast over the Access Grid.  If you would
like to watch this talk at Sydney please contact Robert Pearson.  

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12:30pm, Access Grid Room, University of Wollongong 

Speaker: Jacqui Ramagge 

Title: Infinite groups, geometries and operator algebras 

Abstract: Examples are of critical importance in operators algebras; the lack of
decomposition theorems means we can't use the standard trick of breaking objects down
into simple pieces, studying the pieces and inferring information about the whole.
Infinite groups acting on geometries enable us to generate a surprisingly large class of
examples of operator algebras.  While the impact of the work is in the field of operator
algebras, I will focus on the groups and the geometries, which is where the action is
(pun not originally intended but irresistible once noted).  

2:30pm, room TBA 

Speaker: Anne Thomas 

Title: Infinite generation of non-cocompact lattices on right-angled buildings 

Abstract: Let Gamma be a non-cocompact lattice on a right-angled building X.  Examples
of such X include products of trees, or Bourdon's building I_{p,q}, which has apartments
hyperbolic planes tesselated by right-angled p-gons and all vertex links the complete
bipartite graph K_{q,q}.  We prove that if Gamma has a strict fundamental domain then
Gamma is not finitely generated.  The proof uses a topological criterion for finite
generation and the separation properties of subcomplexes of X called tree-walls.  This
is joint work with Kevin Wortman (Utah).

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