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An edge-coloured cycle is rainbow if the edges have distinct colours. Let $G$ be a graph such that any $k$ vertices lie in a cycle of $G$. The $k$-rainbow cycle index of $G$, denoted by $crx_k(G)$, is the minimum number of colours required…

Combinatorics · Mathematics 2024-05-31 Henry Liu

Hoffman's bound is a well-known spectral bound on the chromatic number of a graph, known to be tight for instance for bipartite graphs. While Hoffman colorings (colorings attaining the bound) were studied before for regular graphs, for…

Combinatorics · Mathematics 2025-01-31 Aida Abiad , Wieb Bosma , Thijs van Veluw

A $k$-edge-coloured graph is colour-balanced if each colour appears equally often. Resolving a conjecture of Pardey and Rautenbach, we show that any colour-balanced $k$-edge-coloured complete graph $K_{2kt}$ contains a perfect matching that…

Combinatorics · Mathematics 2026-04-13 Emma Hogan , Alex Scott , Dmitry Tsarev

Let $G_{n,p}^{[\kappa]}$ denote the space of $n$-vertex edge coloured graphs, where each edge occurs independently with probability $p$. The colour of each existing edge is chosen independently and uniformly at random from the set…

Combinatorics · Mathematics 2025-08-13 Colin Cooper , Alan Frieze

A path in an edge-colored graph $G$ is rainbow if no two edges of it are colored the same. The graph $G$ is rainbow-connected if there is a rainbow path between every pair of vertices. If there is a rainbow shortest path between every pair…

Discrete Mathematics · Computer Science 2023-06-22 Melissa Keranen , Juho Lauri

A \textit{rainbow subgraph} of an edge-colored graph is a subgraph whose edges have distinct colors. The \textit{color degree} of a vertex $v$ is the number of different colors on edges incident to $v$. We show that if $n$ is large enough…

Combinatorics · Mathematics 2012-04-17 Alexandr Kostochka , Florian Pfender , Matthew Yancey

In this paper we consider properly edge-colored graphs, i.e. two edges with the same color cannot share an endpoint, so each color class is a matching. A matching is called \it rainbow \rm if its edges have different colors. The minimum…

Combinatorics · Mathematics 2012-08-29 Andras Gyarfas , Gabor N. Sarkozy

An edge-colored graph $G$ is rainbow connected if any two vertices are connected by a path whose edges have distinct colors. The rainbow connection number of a connected graph $G$, denoted $rc(G)$, is the smallest number of colors that are…

Combinatorics · Mathematics 2011-12-05 Arash Ahadi , Ali Dehghan

A rainbow matching in an edge-colored graph is a matching in which no two edges have the same color. The color degree of a vertex v is the number of different colors on edges incident to v. Kritschgau [Electron. J. Combin. 27(2020)] studied…

Combinatorics · Mathematics 2021-05-25 Wenling Zhou

A rainbow colouring of a connected graph is a colouring of the edges of the graph, such that every pair of vertices is connected by at least one path in which no two edges are coloured the same. Such a colouring using minimum possible…

Discrete Mathematics · Computer Science 2012-05-09 L. Sunil Chandran , Deepak Rajendraprasad

An edge-coloring of a complete graph with a set of colors $C$ is called completely balanced if any vertex is incident to the same number of edges of each color from $C$. Erd\H{o}s and Tuza asked in $1993$ whether for any graph $F$ on $\ell$…

Combinatorics · Mathematics 2022-11-29 Maria Axenovich , Felix Christian Clemen

There has been extensive studies on the following question: given $k$ graphs $G_1,\dots, G_k$ over a common vertex set of size $n$, what conditions on $G_i$ ensures a `colorful' copy of $H$, i.e., a copy of $H$ containing at most one edge…

Combinatorics · Mathematics 2024-01-24 Debsoumya Chakraborti , Jaehoon Kim , Hyunwoo Lee , Hong Liu , Jaehyeon Seo

An edge-coloring of a graph $H$ is a function $\mathcal{C}: E(H) \rightarrow \mathbb{N}$. We say that $H$ is rainbow if all edges of $H$ have different colors. Given a graph $F$, an edge-colored graph $G$ is $F$-rainbow saturated if $G$…

Combinatorics · Mathematics 2025-01-14 Yiduo Xu , Zhen He , Mei Lu

An edge-colored graph $G$, where adjacent edges may be colored the same, is rainbow connected if any two vertices of $G$ are connected by a path whose edges have distinct colors. The rainbow connection number $rc(G)$ of a connected graph…

Combinatorics · Mathematics 2011-05-27 Xueliang Li , Sujuan Liu

A proper vertex coloring of a graph is said to be locally identifying if the sets of colors in the closed neighborhood of any two adjacent non-twin vertices are distinct. The lid-chromatic number of a graph is the minimum number of colors…

Combinatorics · Mathematics 2013-07-11 Daniel Gonçalves , Aline Parreau , Alexandre Pinlou

In this short note, we study pairwise edge-disjoint rainbow spanning trees in properly edge-coloured complete graphs, where a graph is rainbow if its edges have distinct colours. Brualdi and Hollingsworth conjectured that every $K_n$…

Combinatorics · Mathematics 2017-04-25 József Balogh , Hong Liu , Richard Montgomery

For a graph $G$, we define $\sigma_2(G)=min \{d(u)+d(v)| u,v\in V(G), uv\not\in E(G)\}$, or simply denoted by $\sigma_2$. A edge-colored graph is rainbow edge-connected if any two vertices are connected by a path whose edges have distinct…

Combinatorics · Mathematics 2011-01-18 Jiuying Dong , Xueliang Li

A 2-edge-coloured graph $G$ is called {\bf locally complete} if for each vertex $v$, the vertices adjacent to $v$ through edges of the same colour induce a complete subgraph in $G$. Locally complete 2-edge-coloured graphs have nice…

Combinatorics · Mathematics 2024-10-08 Jørgen Bang-Jensen , Jing Huang

We show that for any integer $t \ge 2$, every properly edge colored $n$-vertex graph with average degree at least $(\log n)^{2+o(1)}$ contains a rainbow subdivision of a complete graph of size $t$. Note that this bound is within $(\log…

Combinatorics · Mathematics 2023-10-16 Yan Wang

A rainbow stacking of $r$-edge-colorings $\chi_1, \ldots, \chi_m$ of the complete graph on $n$ vertices is a way of superimposing $\chi_1, \ldots, \chi_m$ so that no edges of the same color are superimposed on each other. We determine a…

Combinatorics · Mathematics 2024-05-24 Noga Alon , Colin Defant , Noah Kravitz
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