Calendar

Posted January 28, 2026

Geometry and Topology Seminar Seminar website

Konrad Wrobel, University of Texas at Austin
Measure equivalence classification of Baumslag-Solitar groups

We complete the classification of Baumslag-Solitar groups up to measure equivalence by showing all Baumslag-Solitar groups with nonunimodular Bass-Serre tree are measure equivalent (i.e., BS(r,s) with r between 1 and s). The proof makes critical use of combinatorial descriptive set theory tools in the measure class preserving setting and passes through the world of measure equivalence of nonunimodular locally compact groups. In particular, as an intermediate step we obtain measure equivalence couplings between all groups of the form Aut(T_{r,s}) for r between 1 and s where T_{r,s} is the directed tree with r incoming edges and s outgoing edges at each vertex. This is joint work with Damien Gaboriau, Antoine Poulin, Anush Tserunyan, and Robin Tucker-Drob.

Posted January 28, 2026

Geometry and Topology Seminar Seminar website

Joshua Sabloff, Haverford College
TBA

Posted January 28, 2026

Geometry and Topology Seminar Seminar website

Nilangshu Bhattacharyya, Louisiana State University
TBA

Posted January 28, 2026

Geometry and Topology Seminar Seminar website

Nir Gadish, University of Pennsylvania
TBA

Posted January 19, 2026

Geometry and Topology Seminar Seminar website

Ettore Marmo, Università degli Studi di Milano-Bicocca
TBA