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In this note we examine the following random graph model: for an arbitrary graph $H$, with quadratic many edges, construct a graph $G$ by randomly adding $m$ edges to $H$ and randomly coloring the edges of $G$ with $r$ colors. We show that…

Combinatorics · Mathematics 2023-04-28 József Balogh , John Finlay , Cory Palmer

An edge-coloured graph is said to be rainbow if no colour appears more than once. Extremal problems involving rainbow objects have been a focus of much research over the last decade as they capture the essence of a number of interesting…

Combinatorics · Mathematics 2025-02-27 Noga Alon , Matija Bucić , Lisa Sauermann , Dmitrii Zakharov , Or Zamir

A total-colored graph is a graph $G$ such that both all edges and all vertices of $G$ are colored. A path in a total-colored graph $G$ is a total rainbow path if its edges and internal vertices have distinct colors. A total-colored graph…

Combinatorics · Mathematics 2015-01-09 Hui Jiang , Xueliang Li , Yingying Zhang

A subgraph of an edge-coloured graph is called rainbow if all its edges have different colours. We prove a rainbow version of the blow-up lemma of Koml\'os, S\'ark\"ozy and Szemer\'edi that applies to almost optimally bounded colourings. A…

Combinatorics · Mathematics 2019-07-24 Stefan Ehard , Stefan Glock , Felix Joos

Let $G$ be an edge-colored graph with $n$ vertices. A subgraph $H$ of $G$ is called a rainbow subgraph of $G$ if the colors of each pair of the edges in $E(H)$ are distinct. We define the minimum color degree of $G$ to be the smallest…

Combinatorics · Mathematics 2017-09-26 Wipawee Tangjai

The rainbow connection number of a graph G is the least number of colours in a (not necessarily proper) edge-colouring of G such that every two vertices are joined by a path which contains no colour twice. Improving a result of Caro et al.,…

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 2011-10-25 Wei Li , Xueliang Li

Let $G = (V, E)$ be a graph on $n$ vertices, and let $c: E \to P$, where $P$ is a set of colors. Let $\delta^c(G) = \min_{v \in V} \{ d^{c}(v) \}$ where $d^c(v)$ is the number of colors on edges incident to a vertex $v$ of $G$. In 2011,…

Combinatorics · Mathematics 2024-11-15 Andrzej Czygrinow , Xiaofan Yuan

We say a graph $H$ is $r$-rainbow-uncommon if the maximum number of rainbow copies of $H$ under an $r$-coloring of $E(K_n)$ is asymptotically (as $n \to \infty$) greater than what is expected from uniformly random $r$-colorings. Via…

A tree in an edge-colored connected graph $G$ is called \emph{a rainbow tree} if no two edges of it are assigned the same color. For a vertex subset $S\subseteq V(G)$, a tree is called an \emph{$S$-tree} if it connects $S$ in $G$. A…

Combinatorics · Mathematics 2016-10-20 Wenjing Li , Xueliang Li , Jingshu Zhang

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

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

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

Given a triangle-free graph $G$ with chromatic number $k$ and a proper vertex coloring $\phi$ of $G$, it is conjectured that $G$ contains an induced rainbow path on $k$ vertices under $\phi$. Scott and Seymour proved the existence of an…

Combinatorics · Mathematics 2026-01-05 N. R. Aravind , Shiwali Gupta , Rogers Mathew

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 by $rc(G)$, is the smallest number of colors that…

Computational Complexity · Computer Science 2011-11-15 Xiaolong Huang , Xueliang Li , Yongtang Shi

A rainbow path in an edge coloured graph is a path in which no two edges are coloured the same. A rainbow colouring of a connected graph G is a colouring of the edges of G such that every pair of vertices in G is connected by at least one…

Discrete Mathematics · Computer Science 2014-04-18 L. Sunil Chandran , Deepak Rajendraprasad , Marek Tesař

An injective $k$-edge-coloring of a graph $G$ is an assignment of colors, i.e. integers in $\{1, \ldots , k\}$, to the edges of $G$ such that any two edges each incident with one distinct endpoint of a third edge, receive distinct colors.…

Data Structures and Algorithms · Computer Science 2021-04-19 Florent Foucaud , Hervé Hocquard , Dimitri Lajou

Motivated by recent work on majority edge-colourings of graphs, we initiate the study of the corresponding problem for hypergraphs. First, sharpening the probabilistic argument by a $KL$ large-deviation estimate, we obtain a sufficient…

Combinatorics · Mathematics 2026-03-31 Jiangdong Ai , Feiyu Nan

For a fixed graph $H$ on $k$ vertices, and a graph $G$ on at least $k$ vertices, we write $G\rightarrow H$ if in any vertex-coloring of $G$ with $k$ colors, there is an induced subgraph isomorphic to $H$ whose vertices have distinct colors.…

Combinatorics · Mathematics 2016-05-23 Maria Axenovich , Ryan Martin

A meta-conjecture of Coulson, Keevash, Perarnau and Yepremyan states that above the extremal threshold for a given spanning structure in a (hyper-)graph, one can find a rainbow version of that spanning structure in any suitably bounded…

Combinatorics · Mathematics 2026-02-25 Amarja Kathapurkar , Patrick Morris , Guillem Perarnau