Seminars Sorted by Series

We analyze volume-preserving actions of product groups on Riemannian manifolds. Under a natural spectral irreducibility assumption, we prove the following dichotomy: Either the action is measurably isometric, in which case there are at most two...

A pair (G,H), where G is a group and H a subgroup, has relative Property T if every isometric action of G on a Hilbert space has a H-fixed point. In a connected Lie group or a lattice G, we characterize subgroups H such that (G,H) has relative...

Let $G$ be a simple $G(\mathbf Q)$-group of $G(\mathbf Q)$-rank at least 2. In 1987 T. N. Venkataramana showed that if $\Gamma \subset G(\mathbf Z)$ is an infinite subgroup whose commensurator is a subgroup of finite index in $G(\mathbf Z)$, then $...

In joint work with Yehuda Shalom, we have proved Margulis' Normal Subgroup Theorem for any discrete subgroup $\Gamma$ of the automorphism group of a locally finite $A_2$-tilde building, $B$, provided that the quotient of $B$ by $\Gamma$ is compact...