Abstract
We are interested in hereditary classes of graphs \({\mathcal {G}}\) such that every graph \(G \in {\mathcal {G}}\) satisfies \(\varvec{\chi }(G) \le \omega (G) + 1\), where \(\chi (G)\) (\(\omega (G)\)) denote the chromatic (clique) number of G. This upper bound is called the Vizing bound for the chromatic number. Apart from perfect graphs few classes are known to satisfy the Vizing bound in the literature. We show that if G is (\(P_6, S_{1, 2, 2}\), diamond)-free, then \(\chi (G) \le \omega (G)+1\), and we give examples to show that the bound is sharp.
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The authors thank the anonymous referees for their suggestions and comments.
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Frédéric Maffray: Partially supported by ANR project STINT under reference ANR-13-BS02-0007.
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Karthick, T., Maffray, F. Vizing Bound for the Chromatic Number on Some Graph Classes. Graphs and Combinatorics 32, 1447–1460 (2016). https://doi.org/10.1007/s00373-015-1651-1
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DOI: https://doi.org/10.1007/s00373-015-1651-1