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Vertex-disjoint rainbow triangles in edge-colored graphs
Discrete Mathematics ( IF 0.7 ) Pub Date : 2020-12-01 , DOI: 10.1016/j.disc.2020.112117
Jie Hu , Hao Li , Donglei Yang

Abstract Let G be an edge-colored graph of order n . The minimum color degree of G , denoted by δ c ( G ) , is the largest integer k such that for every vertex v , there are at least k distinct colors on edges incident to v . We say that an edge-colored graph is rainbow if all its edges have different colors. In this paper, we consider vertex-disjoint rainbow triangles in edge-colored graphs. Li (2013) showed that if δ c ( G ) ≥ ( n + 1 ) ∕ 2 , then G contains a rainbow triangle and the lower bound is tight. Motivated by this result, we prove that if n ≥ 20 and δ c ( G ) ≥ ( n + 2 ) ∕ 2 , then G contains two vertex-disjoint rainbow triangles. In particular, we conjecture that if δ c ( G ) ≥ ( n + k ) ∕ 2 , then G contains k vertex-disjoint rainbow triangles. For any integer k ≥ 2 , we show that if n ≥ 16 k − 12 and δ c ( G ) ≥ n ∕ 2 + k − 1 , then G contains k vertex-disjoint rainbow triangles. Moreover, we provide sufficient conditions for the existence of k edge-disjoint rainbow triangles.

中文翻译:

边彩色图中顶点不相交的彩虹三角形

摘要 令 G 为 n 阶边着色图。G 的最小颜色程度,用 δ c (G) 表示,是最大的整数 k,使得对于每个顶点 v,在与 v 相关的边缘上至少有 k 种不同的颜色。如果一个边色图的所有边都有不同的颜色,我们就说它是彩虹图。在本文中,我们考虑了边彩色图中的顶点不相交彩虹三角形。Li (2013) 表明,如果 δ c ( G ) ≥ ( n + 1 ) ∕ 2 ,则 G 包含一个彩虹三角形并且下界是紧的。受此结果的启发,我们证明如果 n ≥ 20 且 δ c ( G ) ≥ ( n + 2 ) ∕ 2 ,则 G 包含两个顶点不相交的彩虹三角形。特别地,我们推测如果 δ c ( G ) ≥ ( n + k ) ∕ 2 ,则 G 包含 k 个顶点不相交的彩虹三角形。对于任何整数 k ≥ 2 ,我们证明如果 n ≥ 16 k − 12 并且 δ c ( G ) ≥ n ∕ 2 + k − 1 ,那么 G 包含 k 个顶点不相交的彩虹三角形。此外,我们为 k 个边不相交的彩虹三角形的存在提供了充分条件。
更新日期:2020-12-01
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