Title:  Expanders and torsion homology

Speaker:  Jonathan Zung

Abstract: We say that a Riemannian 3-manifold has good higher expansion if every rationally null-homologous i-cycle bounds an i+1 chain of relatively small volume. In this talk, I'll explain how to construct rational homology spheres which are good higher expanders. On the other hand, I will explain that higher expanders must be topologically complicated; in particular, they must have lots of torsion homology.