Abstract
We show that every edge in a 2-edge-connected planar cubic graph is either contained in a 2-edge-cut or is a chord of some cycle contained in a 2-factor of the graph. As a consequence, we show that every edge in a cyclically 4-edge-connected planar cubic graph with at least six vertices is contained in a perfect matching whose removal disconnects the graph. We obtain a complete characterization of 2-edge-connected planar cubic graphs that have an edge such that every 2-factor containing the edge is a Hamiltonian cycle, and also of those that have an edge such that the complement of every perfect matching containing the edge is a Hamiltonian cycle. Another immediate consequence of the main result is that for any two edges contained in a facial cycle of a 2-edge-connected planar cubic graph, there exists a 2-factor in the graph such that both edges are contained in the same cycle of the 2-factor. We conjecture that this property holds for any two edges in a 2-edge-connected planar cubic graph, and prove it in the case the graph is also bipartite. The main result is proved in the dual form by showing that every plane triangulation admits a vertex 3-coloring such that no face is monochromatic and there is exactly one specified edge between a specified pair of color classes.
Similar content being viewed by others
Data Availability
Data sharing not applicable to this article as no datasets were generated or analysed during the current study.
References
Alon, N., Berke, R., Buchin, K., Buchin, M., Csorba, P., Shannigrahi, S., Speckmann, B., Zumstein, P.: Polychromatic colorings of plane graphs. Discret. Comput. Geom. 42, 421–442 (2009)
Barnette, D.W.: Conjecture 5. Recent Progress in Combinatorics. In: Tutte, W.T. (ed.) Proceedings of the Third Waterloo Conference on Combinatorics, May 1968, p. 343. Academic Press, New York (1969)
Diwan, A.A.: Disconnected 2-factors in planar cubic bridgeless graphs. J. Comb. Theory Ser. B 84, 249–259 (2002)
Dvořák, Z., Král, D.: On planar mixed hypergraphs. Electron. J. Comb. 8, 23 (2001)
Funk, M., Jackson, B., Labbate, D., Sheehan, J.: 2-Factor hamiltonian graphs. J. Comb. Theory Ser. B 87, 138–144 (2003)
Häggkvist, R.: Ear decompositions of a cubic bridgeless graph and near \(P_4\)-decompositions of its deck. Electron. Notes Discret. Math. 34, 191–198 (2009)
Hoffmann-Ostenhof, A.: 3-Edge-coloring conjecture. Open problem garden. http://garden.irmacs.sfu.ca/op/3_edge_coloring_conjecture. Accessed 28 Apr 2020
Matsumoto, N., Noguchi, K., Yashima, T.: Cubic graphs having only \(k\) cycles in each 2-factor. Discuss. Math. Graph Theory. https://doi.org/10.7151/dmgt.2447
Penaud, J.G.: Une propriété de bicoloration des hypergraphes planaires (in French). In: Colloque sur la Théorie des Graphes, Paris, 1974, vol. 17, pp. 345–349. Cahiers Centre Études Recherche Opér. Brussels (1975)
Petersen, J.: Die theorie der regulären graphs. Acta Math. 15, 193–220 (1891)
Schönberger, T.: Ein Beweis des Petersenschen Graphensatzes. Acta Sci. Math. Szeged 7, 51–57 (1934)
Acknowledgements
We thank the anonymous reviewers for the detailed comments and suggestions that helped in improving the presentation.
Funding
The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Conflict of interest
The authors declare that they have no conflict of interest.
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
Springer Nature or its licensor holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
About this article
Cite this article
Diwan, A.A. Chords of 2-Factors in Planar Cubic Bridgeless Graphs. Graphs and Combinatorics 38, 177 (2022). https://doi.org/10.1007/s00373-022-02583-y
Received:
Revised:
Accepted:
Published:
DOI: https://doi.org/10.1007/s00373-022-02583-y