On April 6th, the Geometry-Topology Seminar will have a special “away” meeting at the Institute for Advanced Study. Anne Thomas of the University of Sydney will speak on:

**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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