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

Combinatorics · Mathematics 2013-10-10 Tingting Liu , Yumei Hu

For two given graphs $G_1$ and $G_2$, the Ramsey number $R(G_1,G_2)$ is the least integer $r$ such that for every graph $G$ on $r$ vertices, either $G$ contains a $G_1$ or $\bar{G}$ contains a $G_2$. In this note, we determined the Ramsey…

Combinatorics · Mathematics 2015-03-05 Binlong Li , Ingo Schiermeyer

Given simple graphs $H_{1},H_{2},\ldots,H_{c}$, the Ramsey number $r(H_{1},H_{2},\ldots,H_{c})$ is the smallest positive integer $n$ such that every edge-colored $K_{n}$ with $c$ colors contains a subgraph in color $i$ isomorphic to $H_{i}$…

Combinatorics · Mathematics 2020-10-22 Chuandong Xu , Hongna Yang , Shenggui Zhang

The Ramsey number $r_k(s,n)$ is the minimum $N$ such that every red-blue coloring of the $k$-subsets of $\{1, \ldots, N\}$ contains a red set of size $s$ or a blue set of size $n$, where a set is red (blue) if all of its $k$-subsets are red…

Combinatorics · Mathematics 2015-06-01 Dhruv Mubayi , Andrew Suk

Given a graph $G$ and a positive integer $k$, define the \emph{Gallai-Ramsey number} to be the minimum number of vertices $n$ such that any $k$-edge coloring of the complete graph $K_n$ contains either a rainbow (all different colored)…

Combinatorics · Mathematics 2020-07-15 Yaping Mao , Zhao Wang , Colton Magnant , Ingo Sciermeyer

For a fixed graph $H$, we say that an edge-colored graph $G$ is \emph{weakly $H$-rainbow saturated} if there exists an ordering $e_1, e_2, \ldots, e_m$ of $E\left(\overline{G}\right)$ such that, for any list $c_1, c_2, \ldots, c_m$ of…

Combinatorics · Mathematics 2025-01-07 Xihe Li , Jie Ma , Tianying Xie

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

Given two graphs $G$ and $H$, the $k$-colored Gallai-Ramsey number $gr_k(G : H)$ is defined to be the minimum integer $n$ such that every $k$-coloring of the complete graph on $n$ vertices contains either a rainbow copy of $G$ or a…

Combinatorics · Mathematics 2018-11-16 Xihe Li , Ligong Wang

Let $K_n$ denote the complete graph on $n$ vertices and $G, H$ be finite graphs. Consider a two-coloring of edges of $K_n$. When a copy of $G$ in the first color, red, or a copy of $H$ in the second color, blue is in $K_n$, we write…

Combinatorics · Mathematics 2020-09-16 C. J. Jayawardene , W. C. W. Navaratna

Let $P_t$ denote the path on $t$ vertices. The $r$-coloured Ramsey number of $P_t$, denoted by $R_r(P_t)$, is the minimum integer $n$ such that whenever the complete graph on $n$ vertices is given an $r$-edge-colouring, there exists a…

Combinatorics · Mathematics 2021-08-17 Henry Liu , Bojan Mohar , Yongtang Shi

Let $k \in \mathbb{N}$ and let $H_1, H_2, \ldots, H_k$ be simple graphs such that for each $j \in \{ 1, 2, \ldots, k \}$, the vertex set of $H_j$ is $\{ 0, 1, 2, \ldots, n_j - 1 \}$ for some $n_j \in \mathbb{N}$. The ordered Ramsey number…

Combinatorics · Mathematics 2026-04-20 Nino Bašić , Ivan Damnjanović , Dragan Stevanović , Ivan Stošić

Given two graphs $G_1, G_2$, the connected size Ramsey number ${\hat{r}}_c(G_1,G_2)$ is defined to be the minimum number of edges of a connected graph $G$, such that for any red-blue edge colouring of $G$, there is either a red copy of…

Combinatorics · Mathematics 2022-05-10 Sha Wang , Ruyu Song , Yixin Zhang , Yanbo Zhang

We initiate the study of Ramsey numbers of trails. Let $k \geq 2$ be a positive integer. The Ramsey number of trails with $k$ vertices is defined as the the smallest number $n$ such that for every graph $H$ with $n$ vertices, $H$ or the…

Discrete Mathematics · Computer Science 2022-09-14 Masatoshi Osumi

The Ramsey number $r(G,H)$ is the minimum $N$ such that every graph on $N$ vertices contains $G$ as a subgraph or its complement contains $H$ as a subgraph. For integers $n \geq k \geq 1$, the $k$-book $B_{k,n}$ is the graph on $n$ vertices…

Combinatorics · Mathematics 2023-07-17 Jacob Fox , Xiaoyu He , Yuval Wigderson

Given a pair of graphs $G$ and $H$, the Ramsey number $R(G,H)$ is the smallest $N$ such that every red-blue coloring of the edges of the complete graph $K_N$ contains a red copy of $G$ or a blue copy of $H$. If graph $G$ is connected, it is…

Combinatorics · Mathematics 2016-06-28 Alexey Pokrovskiy , Benny Sudakov

For graphs $G, H_1,\dots,H_r$, write $G \to (H_1, \ldots, H_r)$ to denote the property that whenever we $r$-colour the edges of $G$, there is a monochromatic copy of $H_i$ in colour $i$ for some $i \in \{1,\dots,r\}$. Mousset, Nenadov and…

Combinatorics · Mathematics 2025-12-16 Candida Bowtell , Robert Hancock , Joseph Hyde

A graph $G$ is said to be Ramsey for a tuple of graphs $(H_1,\dots,H_r)$ if every $r$-coloring of the edges of $G$ contains a monochromatic copy of $H_i$ in color $i$, for some $i$. A fundamental question at the intersection of Ramsey…

Combinatorics · Mathematics 2024-08-21 Micha Christoph , Anders Martinsson , Raphael Steiner , Yuval Wigderson

An ordered graph $\mathcal{G}$ is a simple graph together with a total ordering on its vertices. The (2-color) Ramsey number of $\mathcal{G}$ is the smallest integer $N$ such that every 2-coloring of the edges of the complete ordered graph…

Combinatorics · Mathematics 2019-02-26 Jesse Geneson , Amber Holmes , Xujun Liu , Dana Neidinger , Yanitsa Pehova , Isaac Wass

For two graphs $G$ and $H$, the Ramsey number $r(G,H)$ is the smallest positive integer $r$, such that any red/blue coloring of the edges of the graph $K_r$ contains either a red subgraph that is isomorphic to $G$ or a blue subgraph that is…

Combinatorics · Mathematics 2015-11-26 Sh. Haghi , H. R. Maimani , A. Seify

The degree anti-Ramsey number $AR_d(H)$ of a graph $H$ is the smallest integer $k$ for which there exists a graph $G$ with maximum degree at most $k$ such that any proper edge colouring of $G$ yields a rainbow copy of $H$. In this paper we…

Combinatorics · Mathematics 2017-05-15 Shoni Gilboa , Dan Hefetz
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