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arXiv · 1310.5875

Colouring quadrangulations of projective spaces

Tomáš Kaiser·Matěj Stehlík
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Abstract

A graph embedded in a surface with all faces of size 4 is known as a quadrangulation. We extend the definition of quadrangulation to higher dimensions, and prove that any graph G which embeds as a quadrangulation in the real projective space P^n has chromatic number n+2 or higher, unless G is bipartite. For n=2 this was proved by Youngs [J. Graph Theory 21 (1996), 219-227]. The family of quadrangulations of projective spaces includes all complete graphs, all Mycielski graphs, and certain graphs homomorphic to Schrijver graphs. As a corollary, we obtain a new proof of the Lovasz-Kneser theorem.

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Tomáš Kaiser, Matěj Stehlík. 2013-10-22. Colouring quadrangulations of projective spaces. https://doi.org/10.1016/j.jctb.2014.12.007

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