Expanders Learning Seminar: Expanders are exotic

Speaker: Rasmus Kløvgaard Stavenuiter

Abstract: We elaborate on the idea that emerged last time that expander families are exotic objects, both in that they are difficult to construct concretely, and in that they are not compatible with Euclidean structure.

More precisely, we will explain in detail Shalom's quantitative proof that the special linear group of order 3, SL(3, Z), gives rise to concrete examples of expanders, as well as Gromov's proof that expanders do not coarsely embed into any Hilbert space.