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Edge‐colorings avoiding rainbow stars
Abstract:We consider an extremal problem motivated by a article of Balogh [J. Balogh, A remark on the number of edge colorings of graphs, European Journal of Combinatorics 27, 2006, 565–573], who considered edge‐colorings of graphs avoiding fixed subgraphs with a prescribed coloring. More precisely, given urn:x-wiley:03649024:media:jgt22165:jgt22165-math-0001, we look for n‐vertex graphs that admit the maximum number of r‐edge‐colorings such that at most urn:x-wiley:03649024:media:jgt22165:jgt22165-math-0002 colors appear in edges incident with each vertex, that is, r‐edge‐colorings avoiding rainbow‐colored stars with t edges. For large n, we show that, with the exception of the case urn:x-wiley:03649024:media:jgt22165:jgt22165-math-0003, the complete graph urn:x-wiley:03649024:media:jgt22165:jgt22165-math-0004 is always the unique extremal graph. We also consider generalizations of this problem.
Keywords:extremal graph theory  edge‐colorings
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