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Cyclic coloration of 3-polytopes. (English) Zbl 0655.05030
The main results in the present paper are concerned with 3-connected planar graphs which are just the family of “3-polytopes” by a celebrated theorem of Steinitz. By a classical result due to Whitney there is essentially only one way to imbed them in the plane. A cyclic coloration of a planar graph G is an assignment of colors to the points of G such that for any face-bounding cycle F of G, the points of F have different colors. The cyclic coloration number $$\chi_ c(G)$$ is the minimum number of colors in any cyclic coloration of G. The main result in this paper asserts that $$\chi_ c(G)\leq \rho$$ $$*(G)+9$$ for every 3- connected plane graph G with maximum face size $$\rho$$ *(G), thus improving the upper bound $$2\rho$$ *(G), due to O. Ore and the first author [Recent Prog. Comb., Proc. 3rd Waterloo Conf. 1968, 287-293 (1969; Zbl 0195.257)]. The proof uses two principal tools: the theory of Euler contributions and recent results on contractible lines in 3-connected graphs by K. Ando, H. Enomoto and A. Saito. If $$\rho$$ *(G) is sufficiently small or suffuciently large, this bound can be improved.
Reviewer: I.Tomescu

##### MSC:
 05C15 Coloring of graphs and hypergraphs
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##### References:
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