Seminar: Alina Vdovina (City College of New York and Graduate Center, CUNY): "Higher dimensional digraphs from cube complexes and their spectral theory"

Zoom link: https://harvard.zoom.us/j/779283357?pwd=MitXVm1pYUlJVzZqT3lwV2pCT1ZUQT09
Speaker: Alina Vdovina (City College of New York and Graduate Center, CUNY)
Title: Higher dimensional digraphs from cube complexes and their spectral theory
Abstract: We define k-dimensional digraphs and initiate a study of their spectral theory. The k-dimensional digraphs can be viewed as generating graphs for small categories called k-graphs. Guided by geometric insight, we obtain several new series of k-graphs using cube complexes covered by Cartesian products of trees, for k≥2. These k-graphs can not be presented as virtual products, and constitute novel models of such small categories. The constructions yield rank-k Cuntz-Krieger algebras for all k≥2. We introduce Ramanujan k-graphs satisfying optimal spectral gap property, and show explicitly how to construct the underlying k-digraphs.