Oriented colorings of 2-outerplanar graphs |
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Authors: | Louis Esperet |
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Affiliation: | LaBRI UMR CNRS 5800, Université Bordeaux I, 33405 Talence Cedex, France |
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Abstract: | A graph G is 2-outerplanar if it has a planar embedding such that the subgraph obtained by removing the vertices of the outer face is outerplanar. The oriented chromatic number of an oriented graph H is defined as the minimum order of an oriented graph H′ such that H has a homomorphism to H′. In this paper, we prove that 2-outerplanar graphs are 4-degenerate. We also show that oriented 2-outerplanar graphs have a homomorphism to the Paley tournament QR67, which implies that their (strong) oriented chromatic number is at most 67. |
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Keywords: | Combinatorial problems Oriented coloring 2-outerplanar graphs |
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