Sphericity, cubicity, and edge clique covers of graphs

  • Authors:
  • T. S. Michael;Thomas Quint

  • Affiliations:
  • Mathematics Department, United States Naval Academy, Annapolis, MD;Department of Mathematics and Statistics, University of Nevada, Reno, NV

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2006

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Abstract

The sphericity sph(G) of a graph G is the minimum dimension d for which G is the intersection graph of a family of congruent spheres in Rd. The edge clique cover number θ(G) is the minimum cardinality of a set of cliques (complete subgraphs) that covers all edges of G. We prove that if G has at least one edge, then sph(G) ≤θ(G). Our upper bound remains valid for intersection graphs defined by balls in the Lp-norm for 1 ≤ p ≤ ∞