Bounding χ in terms of ω and Δ for quasi-line graphs

  • Authors:
  • Andrew D. King;Bruce A. Reed

  • Affiliations:
  • School of Computer Science, McGill University, Montreal, Quebec, Canada;School of Computer Science, McGill University, Montreal, Quebec, Canada

  • Venue:
  • Journal of Graph Theory
  • Year:
  • 2008

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Abstract

A quasi-line graph is a graph in which the neighborhood of any vertex can be covered by two cliques; every line graph is a quasi-line graph. Reed conjectured that for any graph G, $\chi({{G}}) \leq\left \lceil {{{1}}\over {{2}}}(\Delta({{G}})+{{1}}+\omega({{G}}))\right\rceil$ [Reed, J Graph Theory 27 (1998), 177–212]. We prove that the conjecture holds if G is a quasi-line graph, extending a result of King et al. who proved the conjecture for line graphs [Eur J Comb 28 (2007), 2182–2187], and improving the bound of $\chi{{(}}{{G}}{{)}} \leq {3\over 2} \omega({{G}})$ given by Chudnovsky and Ovetsky [J Graph Theory 54 (2007), 41–50]. © 2008 Wiley Periodicals, Inc. J Graph Theory 59: 215–228, 2008