Spring 2017

Ramanujan Covers

Monday, Jan. 30, 2017 2:55 pm3:40 pm PST

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Calvin Lab Auditorium

The breakthrough work of Marcus, Spielman, and Srivastava showed that every bipartite Ramanujan graph has a bipartite Ramanujan double cover. Chris Hall, Doron Puder, and I generalized this to covers of arbitrary degree. I will explain the proof, with emphasis on how group theory and representation theory are useful for this problem.