Abstract
We show that, given an infinite cardinal μ, a graph has colouring number at most μ if and only if it contains neither of two types of subgraph. We also show that every graph with infinite colouring number has a well-ordering of its vertices that simultaneously witnesses its colouring number and its cardinality.
Similar content being viewed by others
References
B. Dushnik and E. W. Miller: Partially ordered sets, Amer. J. Math.63 (1941), 600–610.
P. Erdős and A. Hajnal, A.: On chromatic number of graphs and set-systems, Acta Math. Acad. Sci. Hungar17 (1966), 61–99.
R. Halin. Graphentheorie, Wissenschaftliche Buchgesellschaft, Darmstadt, 2 edition, 1989.
P. Komjáth: Infinite graphs, Research Monograph. In Preparation.
P. Komjáth: A note on uncountable chordal graphs, Discrete Math.338 (2015), 1565–1566.
P. Komjáth: Hadwiger's conjecture for uncountable graphs, Abh. Math. Semin. Univ. Hambg.87 (2017), 337–341.
K. Kunen: Set theory, volume 34 of Studies in Logic (London), College Publications, London, 2011.
S. Shelah: A compactness theorem for singular cardinals, free algebras, whitehead problem and transversals, Israel J. Math.21 (1975), 319–349.
S. Shelah: Notes on partition calculus, Colloq. Math. Soc. János Bolyai, Vol. 10. 1975, 1257–1276.
W. Sierpiński: Sur un problème de la théorie des relations, Ann. Scuola Norm. Sup. Pisa Cl. Sci. (2)2 (1933), 285–287.
Acknowledgments
We thank the first referee of this paper for pointing out to mention Theorem 1.5 in the Introduction and Lemma 2.7.
Author information
Authors and Affiliations
Corresponding authors
Additional information
This research was supported by Thematic Excellence Programme, Industry and Digitization Subprogramme, NRDI Office, 2019.
Rights and permissions
About this article
Cite this article
Bowler, N., Carmesin, J., Komjáth, P. et al. The Colouring Number of Infinite Graphs. Combinatorica 39, 1225–1235 (2019). https://doi.org/10.1007/s00493-019-4045-9
Received:
Revised:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00493-019-4045-9