Ramanujan graphs are regular graphs whose vertex adjacency matrix has “very condensed” spectrum. The latter manifests in many desired combinatorial properties, most notable of which is the fact that Ramanujan graphs are expanders, i.e. they admit high connectivity among their … Continue reading Colloquium: Tuesday, December 27, 12 pm. Speaker: Uriya First (UBC). Title: “Ramanujan Complexes”.