A characterization of triangle-free tolerance graphs

  • Authors:
  • Arthur H. Busch

  • Affiliations:
  • Department of Mathematics, University of Colorado at Denver, Denver, CO 80217, USA

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

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Abstract

We prove that a triangle-free graph G is a tolerance graph if and only if there exists a set of consecutively ordered stars that partition the edges of G. Since tolerance graphs are weakly chordal, a tolerance graph is bipartite if and only if it is triangle-free. We, therefore, characterize those tolerance graphs that are also bipartite. We use this result to show that in general, the class of interval bigraphs properly contains tolerance graphs that are triangle-free (and hence bipartite).