English

Rainbow triangles in edge-colored complete graphs

Combinatorics 2020-12-04 v1

Abstract

Let GG be a graph of order nn with an edge-coloring cc, and let δc(G)\delta^c(G) denote the minimum color-degree of GG. A subgraph FF of GG is called rainbow if any two edges of FF have distinct colors. There have been a lot results in the existing literature on rainbow triangles in edge-colored complete graphs. Fujita and Magnant showed that for an edge-colored complete graph GG of order nn, if δc(G)n+12\delta^c(G)\geq \frac{n+1}{2}, then every vertex of GG is contained in a rainbow triangle. In this paper, we show that if δc(G)n+k2\delta^c(G)\geq \frac{n+k}{2}, then every vertex of GG is contained in at least kk rainbow triangles, which can be seen as a generalization of their result. Li showed that for an edge-colored graph GG of order nn, if δc(G)n+12\delta^c(G)\geq \frac{n+1}{2}, then GG contains a rainbow triangle. We show that if GG is complete and δc(G)n2\delta^c(G)\geq \frac{n}{2}, then GG contains a rainbow triangle and the bound is sharp. Hu et al. showed that for an edge-colored graph GG of order n20n\geq 20, if δc(G)n+22\delta^c(G)\geq \frac{n+2}{2}, then GG contains two vertex-disjoint rainbow triangles. We show that if GG is complete with order n8n\geq 8 and δc(G)n+12\delta^c(G)\geq \frac{n+1}{2}, then GG contains two vertex-disjoint rainbow triangles. Moreover, we improve the result of Hu et al. from n20n\geq 20 to n7n\geq 7, the best possible.

Keywords

Cite

@article{arxiv.2012.01716,
  title  = {Rainbow triangles in edge-colored complete graphs},
  author = {Xiaozheng Chen and Xueliang Li},
  journal= {arXiv preprint arXiv:2012.01716},
  year   = {2020}
}

Comments

10 pages, 4 figures

R2 v1 2026-06-23T20:41:43.677Z