Diameters of Polyhedral Graphs

Abstract

The distance between two vertices of a connected finite graph is the smallest number of edges forming a path that joins the two vertices, and the diameter of the graph is the largest integer which is realized as the distance between two vertices of the graph. We are concerned here with the diameters of two graphs associated with a d-dimensional convex polytope P (called henceforth a d-polytope). The graph Γ(P) of P is the 1- complex formed by the vertices and edges of P , and the polar graph II (P) of P is the 1-complex whose vertices correspond to the (d — 1)-faces of P, with two vertices joined by an edge in II (P) if and only if the corresponding (d — 1)- faces intersect in a (d — 2)-face of P. The diameters of Γ(P) and II (P) will be denoted respectively by δ(P) (called the diameter of P) and ϕ(Ps) (called the face-diameter of P ).