β-Differential of a GraphLudwin A. Basilio, Sergio Bermudo, Jesús Leaños, Jose Maria SigarretaSymmetry2017Let G = (V, E) be a simple graph with vertex set V and edge set E. Let D be a subset of V, and let B(D) be the set of neighbours of D in V \ D. The differential ∂(D) of D is defined as |B(D)| − |D|.… (More)