Thursday, November 20
Angela Kubena Barnhill, Northwestern University
In the Lie group setting, Margulis proved that a lattice is arithmetic if and only if its commensurator is dense. In the case of automorphism groups of trees, Liu showed that every cocompact lattice has dense commensurator. We consider commensurators of cocompact lattices in the automorphism groups of right-angled buildings and show that the commensurator of the "standard lattice" is dense. This is joint work with Anne Thomas.
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