Triangle-free graphs and forbidden subgraphs

  • Authors:
  • Stephan Brandt

  • Affiliations:
  • TU Ilmenau, Fak. für Mathematik und Naturwissenschaften, Postfach 100 565, 98684 Ilmenau, Germany

  • Venue:
  • Discrete Applied Mathematics - Sixth Twente Workshop on Graphs and Combinatorial Optimization
  • Year:
  • 2002

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Abstract

The relation of chromatic aspects and the existence of certain induced subgraphs of a triangle-free graph will be investigated. Based on a characterization statement of Pach, some results on the chromatic number of triangle-free graphs with certain forbidden induced subgraphs will be refined by describing their structure in terms of homomorphisms. In particular, we introduce chordal triangle-free graphs as a natural superclass of chordal bipartite graphs and describe the structure of the maximal triangle-free members. Finally, we improve on the upper bound for the chromatic number of triangle-free sK2-free graphs by 1 for s ≥ 2, giving the tight bound for s = 3.