Abstract
For a nontrivial connected graph G, let c: V (G) → ℕ be a vertex coloring of G where adjacent vertices may be colored the same. For a vertex v of G, the neighborhood color set NC(v) is the set of colors of the neighbors of v. The coloring c is called a set coloring if NC(u) ≠ NC(v) for every pair u, v of adjacent vertices of G. The minimum number of colors required of such a coloring is called the set chromatic number x s (G). A study is made of the set chromatic number of the join G+H of two graphs G and H. Sharp lower and upper bounds are established for x s (G + H) in terms of x s (G), x s (H), and the clique numbers ω(G) and ω(H).
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G. Chartrand, F. Okamoto, C.W. Rasmussen, P. Zhang: The set chromatic number of a graph. Discuss. Math. Graph Theory. To appear.
G. Chartrand, P. Zhang: Chromatic Graph Theory. Chapman & Hall/CRC Press, Boca Raton, 2008.
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Okamoto, F., Rasmussen, C.W. & Zhang, P. Set vertex colorings and joins of graphs. Czech Math J 59, 929–941 (2009). https://doi.org/10.1007/s10587-009-0064-9
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DOI: https://doi.org/10.1007/s10587-009-0064-9