English

The odd chromatic number of a toroidal graph is at most 9

Combinatorics 2022-06-14 v1

Abstract

It's well known that every planar graph is 44-colorable. A toroidal graph is a graph that can be embedded on a torus. It's proved that every toroidal graph is 77-colorable. A proper coloring of a graph is called \emph{odd} if every non-isolated vertex has at least one color that appears an odd number of times in its neighborhood. The smallest number of colors that admits an odd coloring of a graph G G is denoted by χo(G)\chi_{o}(G). In this paper, we prove that if GG is tortoidal, then χo(G)9\chi_{o}\left({G}\right)\le9; Note that K7K_7 is a toroidal graph, the upper bound is no less than 77.

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Cite

@article{arxiv.2206.05780,
  title  = {The odd chromatic number of a toroidal graph is at most 9},
  author = {Fangyu Tian and Yuxue Yin},
  journal= {arXiv preprint arXiv:2206.05780},
  year   = {2022}
}

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9 pages