Local Spectral Expansion Approach to High Dimensional Expanders Part II: Mixing and Geometrical overlapping

Abstract: In this paper, we further explore the local-to-global approach for expansion of simplicial complexes that we call local spectral expansion. Specifically, we prove that local expansion in the links imply the global expansion phenomena of mixing and geometric overlapping. Our mixing results also give tighter bounds on the error terms compared to previously known results.