Giles Gardam

GGT Seminar: Tim de Laat (Münster): Origami expanders

Thursday, 20.01.2022 15:00 im Raum SRZ 216/217

Mathematik und Informatik

We construct a new type of expanders, from measure-preserving affine actions with spectral gap on origami surfaces, in each genus g > 0. These actions are the first examples of actions with spectral gap on surfaces of genus g > 1. We prove that the new expanders are coarsely distinct from the classical expanders obtained via the Laplacian as Cayley graphs of finite quotients of a group. In genus g = 1, this implies that the Margulis expander, and hence the Gabber-Galil expander, is coarsely distinct from the Selberg expander. This is joint work with Goulnara Arzhantseva, Dawid Kielak and Damian Sawicki.

Angelegt am Friday, 19.11.2021 10:26 von Giles Gardam
Geändert am Wednesday, 19.01.2022 15:11 von Giles Gardam
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