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

Computational Complexity · Computer Science 2009-02-17 Sourav Chakraborty , Eldar Fischer , Arie Matsliah , Raphael Yuster

An edge coloring of a simple graph $G$ is said to be \textit{proper rainbow-cycle-forbidding} (PRCF, for short) if no two incident edges receive the same color and for any cycle in $G$, at least two edges of that cycle receive the same…

Combinatorics · Mathematics 2021-06-11 Matt Noble

Let $G$ be a graph of order $n$ with an edge-coloring $c$, and let $\delta^c(G)$ denote the minimum color-degree of $G$. A subgraph $F$ of $G$ is called rainbow if any two edges of $F$ have distinct colors. There have been a lot results in…

Combinatorics · Mathematics 2020-12-04 Xiaozheng Chen , Xueliang Li

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

Combinatorics · Mathematics 2008-09-16 Sourav Chakraborty , Eldar Fischer , Arie Matsliah , Raphael Yuster

Given a graph $G=(V,E)$ on $n$ vertices and an assignment of colours to its edges, a set of edges $S \subseteq E$ is said to be rainbow if edges from $S$ have pairwise different colours assigned to them. In this paper, we investigate…

Combinatorics · Mathematics 2023-11-02 Deepak Bal , Alan Frieze , Pawel Pralat

Let $G$ be an edge-coloured graph. A rainbow subgraph in $G$ is a subgraph such that its edges have distinct colours. The minimum colour degree $\delta^c(G)$ of $G$ is the smallest number of distinct colours on the edges incident with a…

Combinatorics · Mathematics 2015-06-11 Allan Lo

A path in an edge colored graph is said to be a rainbow path if no two edges on the path have the same color. An edge colored graph is (strongly) rainbow connected if there exists a (geodesic) rainbow path between every pair of vertices.…

Discrete Mathematics · Computer Science 2011-10-10 Prabhanjan Ananth , Meghana Nasre , Kanthi K Sarpatwar

The rainbow arborescence conjecture posits that if the arcs of a directed graph with $n$ vertices are colored by $n-1$ colors such that each color class forms a spanning arborescence, then there is a spanning arborescence that contains…

Combinatorics · Mathematics 2025-12-10 Kristóf Bérczi , Tamás Király , Yutaro Yamaguchi , Yu Yokoi

A famous conjecture of Caccetta and H\"{a}ggkvist (CHC) states that a directed graph $D$ with $n$ vertices and minimum outdegree at least $r$ has a directed cycle of length at most $\lceil \frac{n}{r}\rceil$. In 2017, Aharoni proposed the…

Combinatorics · Mathematics 2023-11-22 Xiaozheng Chen , Shanshan Guo , Fei Huang

Let $G = (V,E)$ be an $n$-vertex graph and let $c: E \to \mathbb{N}$ be a coloring of its edges. Let $d^c(v)$ be the number of distinct colors on the edges at $v \in V$ and let $\delta^c(G) = \min_{v \in V} \{ d^{c}(v) \}$. H. Li proved…

Combinatorics · Mathematics 2024-07-12 Andrzej Czygrinow , Theodore Molla , Brendan Nagle

Given an $n$-vertex graph $G$ with minimum degree at least $d n$ for some fixed $d > 0$, the distribution $G \cup \mathbb{G}(n,p)$ over the supergraphs of $G$ is referred to as a (random) {\sl perturbation} of $G$. We consider the…

Combinatorics · Mathematics 2020-04-21 Elad Aigner-Horev , Dan Hefetz

A cycle in an edge-colored graph is said to be rainbow if no two of its edges have the same color. For a complete, infinite, edge-colored graph $G$, define $\mathfrak{S}(G)=\{n\ge 2\;|\;\text{no $n$-cycle of $G$ is rainbow}\}$. Then…

Combinatorics · Mathematics 2015-09-21 Petr Vojtěchovský

The {\em rainbow vertex-connection number}, $rvc(G)$, of a connected graph $G$ is the minimum number of colors needed to color its vertices such that every pair of vertices is connected by at least one path whose internal vertices have…

Combinatorics · Mathematics 2011-10-27 Xueliang Li , Sujuan Liu

An edge-coloured path is \emph{rainbow} if all the edges have distinct colours. For a connected graph $G$, the \emph{rainbow connection number} $rc(G)$ is the minimum number of colours in an edge-colouring of $G$ such that, any two vertices…

Combinatorics · Mathematics 2017-04-21 Lin Chen , Xueliang Li , Henry Liu , Jinfeng Liu

An edge-colored graph $G$, where adjacent edges may have the same color, is {\it rainbow connected} if every two vertices of $G$ are connected by a path whose edge has distinct colors. A graph $G$ is {\it $k$-rainbow connected} if one can…

Combinatorics · Mathematics 2012-03-15 Hengzhe Li , Xueliang Li , Yuefang Sun , Yan Zhao

Let $G$ be an edge-colored graph, a walk in $G$ is said to be a properly colored walk iff each pair of consecutive edges have different colors, including the first and the last edges in case that the walk be closed. Let $H$ be a graph…

A famous conjecture of Caccetta and H\"aggkvist is that in a digraph on $n$ vertices and minimum out-degree at least $\frac{n}{r}$ there is a directed cycle of length $r$ or less. We consider the following generalization: in an undirected…

Combinatorics · Mathematics 2018-04-05 Ron Aharoni , Ron Holzman , Matthew DeVos

The rainbow number ${\rm rb}(G, H)$ is the minimum number of colors $k$ for which any edge-coloring of $G$ with at least $k$ colors guarantees a rainbow subgraph isomorphic to $H$. The rainbow number has many applications in diverse fields…

Combinatorics · Mathematics 2025-12-30 Mengyao Dai , Xin Zhang

A rainbow subgraph of an edge-coloured graph has all edges of distinct colours. A random d-regular graph with d even, and having edges coloured randomly with d/2 of each of n colours, has a rainbow Hamilton cycle with probability tending to…

Combinatorics · Mathematics 2007-05-23 Svante Janson , Nicholas Wormald

Let $G$ be an edge-colored connected graph. A path of $G$ is called rainbow if its every edge is colored by a distinct color. $G$ is called rainbow connected if there exists a rainbow path between every two vertices of $G$. The minimum…

Combinatorics · Mathematics 2013-04-04 Jiuying Dong , Xueliang Li