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A Gallai coloring is a coloring of the edges of a complete graph without rainbow triangles, and a Gallai $k$-coloring is a Gallai coloring that uses at most $k$ colors. For an integer $k\geq 1$, the Gallai-Ramsey number $GR_k(H)$ of a given…

Combinatorics · Mathematics 2020-09-17 Fangfang Zhang , Zi-Xia Song , Yaojun Chen

We call a subgraph of an edge-colored graph rainbow subgraph, if all of its edges have different colors. The anti-Ramsey number of a graph $G$ in a complete graph $K_{n}$, denoted by $ar(K_{n}, G)$, is the maximum number of colors in an…

Combinatorics · Mathematics 2019-08-13 Chunqiu Fang , Ervin Győri , Mei Lu , Jimeng Xiao

A Gallai-coloring (Gallai-$k$-coloring) is an edge-coloring (with colors from $\{1, 2, \ldots, k\}$) of a complete graph without rainbow triangles. Given a graph $H$ and a positive integer $k$, the $k$-colored Gallai-Ramsey number $GR_k(H)$…

Combinatorics · Mathematics 2022-03-23 Xihe Li , Hajo Broersma , Ligong Wang

A Gallai coloring of a complete graph is an edge-coloring such that no triangle has all its edges colored differently. A Gallai $k$-coloring is a Gallai coloring that uses $k$ colors. Given an integer $k\ge1$ and a graph $H$, the…

Combinatorics · Mathematics 2018-08-31 Christian Bosse , Zi-Xia Song , Jingmei Zhang

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 $K_n$ contains either a rainbow (all different colored) triangle or a…

Combinatorics · Mathematics 2019-03-01 Yaping Mao , Zhao Wang , Colton Magnant , Ingo Schiermeyer

For two graph H and G, the Ramsey number r(H, G) is the smallest positive integer n such that every red-blue edge coloring of the complete graph K_n on n vertices contains either a red copy of H or a blue copy of G. Motivated by questions…

Combinatorics · Mathematics 2007-06-29 Benny Sudakov

The Ramsey number r(H) of a graph H is the smallest number n such that, in any two-colouring of the edges of K_n, there is a monochromatic copy of H. We study the Ramsey number of graphs H with t vertices and density \r, proving that r(H)…

Combinatorics · Mathematics 2014-02-26 David Conlon

For an integer $q\ge 2$, a graph $G$ is called $q$-Ramsey for a graph $H$ if every $q$-colouring of the edges of $G$ contains a monochromatic copy of $H$. If $G$ is $q$-Ramsey for $H$, yet no proper subgraph of $G$ has this property then…

Combinatorics · Mathematics 2020-08-12 Dennis Clemens , Anita Liebenau , Damian Reding

For a graph $H$ and an integer $k\ge1$, the $k$-color Ramsey number $R_k(H)$ is the least integer $N$ such that every $k$-coloring of the edges of the complete graph $K_N$ contains a monochromatic copy of $H$. Let $C_m$ denote the cycle on…

Combinatorics · Mathematics 2020-09-18 Fangfang Zhang , Zi-Xia Song , Yaojun Chen

The canonical Ramsey theorem of Erd\H{o}s and Rado implies that for any graph $H$, any edge-coloring (with an arbitrary number of colors) of a sufficiently large complete graph $K_N$ contains a monochromatic, lexicographic, or rainbow copy…

Combinatorics · Mathematics 2024-10-14 Lior Gishboliner , Aleksa Milojević , Benny Sudakov , 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 a graph $G$ is connected, it…

Combinatorics · Mathematics 2016-11-09 Igor Balla , Alexey Pokrovskiy , Benny Sudakov

Let $G_1, G_2, ..., G_t$ be graphs. The multicolor Ramsey number $R(G_1, G_2, ..., G_t)$ is the smallest positive integer $n$ such that if the edges of complete graph $K_n$ are partitioned into $t$ disjoint color classes giving $t$ graphs…

Combinatorics · Mathematics 2012-07-17 Leila Maherani , Gholamreza Omidi , Ghaffar Raeisi , Maryam Shahsiah

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

Given a positive integer $s$, a graph $G$ is $s$-Ramsey for a graph $H$, denoted $G\rightarrow (H)_s$, if every $s$-colouring of the edges of $G$ contains a monochromatic copy of $H$. The $s$-colour size-Ramsey number ${\hat{r}}_s(H)$ of a…

Combinatorics · Mathematics 2018-11-05 Jie Han , Matthew Jenssen , Yoshiharu Kohayakawa , Guilherme Oliveira Mota , Barnaby Roberts

The $r$-size-Ramsey number $\hat{R}_r(H)$ of a graph $H$ is the smallest number of edges a graph $G$ can have, such that for every edge-coloring of $G$ with $r$ colors there exists a monochromatic copy of $H$ in $G$. For a graph $H$, we…

Combinatorics · Mathematics 2020-11-12 Nemanja Draganić , Michael Krivelevich , Rajko Nenadov

Given two graphs $G$ and $H$, the {Ramsey number} $R(G,H)$ is the smallest positive integer $N$ such that every 2-coloring of the edges of $K_{N}$ contains either a red $G$ or a blue $H$. Let $K_{N-1}\sqcup K_{1,k}$ be the graph obtained…

Combinatorics · Mathematics 2023-08-22 Taiping Jiang , Xinmin Hou

Given a graph $H$, the Ramsey number $r(H)$ is the smallest natural number $N$ such that any two-colouring of the edges of $K_N$ contains a monochromatic copy of $H$. The existence of these numbers has been known since 1930 but their…

Combinatorics · Mathematics 2015-05-12 David Conlon , Jacob Fox , Benny Sudakov

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 $K_n$ contains either a rainbow (all different colored) triangle or a…

Combinatorics · Mathematics 2019-05-30 Yaping Mao , Zhao Wang , Colton Magnant , Ingo Schiermeyer

Given positive integers $k$ and $\ell$ we write $G \rightarrow (K_k,K_\ell)$ if every 2-colouring of the edges of $G$ yields a red copy of $K_k$ or a blue copy of $K_\ell$ and we denote by $R(k)$ the minimum $n$ such that $K_n\rightarrow…

Combinatorics · Mathematics 2025-11-06 Walner Mendonça , Meysam Miralaei , Guilherme O. Mota

For two graphs $G,H$ and a positive integer $k$, the \emph{Gallai-Ramsey number} $\operatorname{gr}_k(G,H)$ is defined as the minimum number of vertices $n$ such that any $k$-edge-coloring of $K_n$ contains either a rainbow (all different…

Combinatorics · Mathematics 2023-01-31 Zhao Wang , Yaping Mao , Ran Gu , Suping Cui , Hengzhe Li