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For a graph G=(V,E), a hypergraph H is called Berge-G if there is a bijection f from E(G) to E(H) such that for each e in E(G), e is a subset of f(e). The set of all Berge-G hypergraphs is denoted B(G). For integers k>1, r>1, and a graph G,…

Combinatorics · Mathematics 2018-09-13 Maria Axenovich , Andras Gyarfas

The $k$-edge-colored bipartite Gallai-Ramsey number $\operatorname{bgr}_k(G:H)$ is defined as the minimum integer $n$ such that $n^2\geq k$ and for every $N\geq n$, every edge-coloring (using all $k$ colors) of complete bipartite graph…

Combinatorics · Mathematics 2023-12-15 Weizhen Chen , Meng Ji , Yaping Mao , Meiqin Wei

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

An ordered graph is a pair $\mathcal{G}=(G,\prec)$ where $G$ is a graph and $\prec$ is a total ordering of its vertices. The ordered Ramsey number $\overline{R}(\mathcal{G})$ is the minimum number $N$ such that every ordered complete graph…

Combinatorics · Mathematics 2020-01-22 Martin Balko , Josef Cibulka , Karel Král , Jan Kynčl

We study off-diagonal Ramsey numbers $r(H, K_n^{(k)})$ of $k$-uniform hypergraphs, where $H$ is a fixed linear $k$-uniform hypergraph and $K_n^{(k)}$ is complete on $n$ vertices. Recently, Conlon et al.\ disproved the folklore conjecture…

Combinatorics · Mathematics 2025-07-10 Xiaoyu He , Jiaxi Nie , Yuval Wigderson , Hung-Hsun Hans Yu

For graphs $G^<$ and $H^<$ with linearly ordered vertex sets, the \ordered Ramsey number $r_<(G^<,H^<)$ is the smallest positive integer $N$ such that any red-blue coloring of the edges of the complete ordered graph $K^<_N$ on $N$ vertices…

Combinatorics · Mathematics 2023-05-30 Martin Balko , Marian Poljak

The size-Ramsey number of a graph $F$ is the smallest number of edges in a graph $G$ with the Ramsey property for $F$, that is, with the property that any 2-colouring of the edges of $G$ contains a monochromatic copy of $F$. We prove that…

Combinatorics · Mathematics 2023-06-22 Dennis Clemens , Meysam Miralaei , Damian Reding , Mathias Schacht , Anusch Taraz

In a $(G^1,G^2)$ coloring of a graph $G$, every edge of $G$ is in $G^1$ or $G^2$. For two bipartite graphs $H_1$ and $H_2$, the bipartite Ramsey number $BR(H_1, H_2)$ is the least integer $b\geq 1$, such that for every $(G^1, G^2)$ coloring…

Combinatorics · Mathematics 2022-02-11 Yaser Rowshan

A graph G is r-Ramsey for a graph H, denoted by G\rightarrow (H)_r, if every r-colouring of the edges of G contains a monochromatic copy of H. The graph G is called r-Ramsey-minimal for H if it is r-Ramsey for H but no proper subgraph of G…

Combinatorics · Mathematics 2015-02-11 Jacob Fox , Andrey Grinshpun , Anita Liebenau , Yury Person , Tibor Szabo

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

For given simple graphs $G_1$ and $G_2$, the size Ramsey number $\hat{R}(G_1,G_2)$ is the smallest positive integer $m$, where there exists a graph $G$ with $m$ edges such that in any edge coloring of $G$ with two colors red and blue, there…

Combinatorics · Mathematics 2017-02-07 Ramin Javadi , Gholamreza Omidi

Given two non-empty graphs $G,H$ and a positive integer $k$, the Gallai-Ramsey number $\operatorname{gr}_k(G:H)$ is defined as the minimum integer $N$ such that for all $n\geq N$, every $k$-edge-coloring of $K_n$ contains either a rainbow…

Combinatorics · Mathematics 2021-10-08 Jinyu Zou , Zhao Wang , Hong-Jian Lai , Yaping Mao

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

Bipartite Ramsey numbers is the smallest size of a complete bipartite graph $K_{N,N}$ such that every edge-coloring with a given number of colors inevitably yields a monochromatic copy of a prescribed bipartite graph. While exact values…

Combinatorics · Mathematics 2026-04-29 Meng Ji

Given an acyclic oriented graph $\vec{H}$ and a graph $G$, we write $G \to \vec{H}$ if every orientation of $G$ has an oriented copy of $\vec{H}$. We define $\vec{R}(\vec{H})$ as the smallest number $n$ such that there exists a graph $G$…

Combinatorics · Mathematics 2020-12-21 Bruno Pasqualotto Cavalar

Given a vertex-ordered graph $G$, the ordered Ramsey number $r_<(G)$ is the minimum integer $N$ such that every $2$-coloring of the edges of the complete ordered graph $K_N$ contains a monochromatic ordered copy of $G$. Motivated by a…

Combinatorics · Mathematics 2024-12-24 Domagoj Bradač , Patryk Morawski , Benny Sudakov , Yuval Wigderson

A $k$-ordering of a graph $G$ assigns distinct order-labels from the set $\{1,\ldots,|G|\}$ to $k$ vertices in $G$. Given a $k$-ordering $H$, the ordered Ramsey number $R_<(H)$ is the minimum $n$ such that every edge-2-coloring of the…

Combinatorics · Mathematics 2017-02-08 Kevin Chang

Burr and Erd\H{o}s in 1975 conjectured, and Chv\'atal, R\"odl, Szemer\'edi and Trotter later proved, that the Ramsey number of any bounded degree graph is linear in the number of vertices. In this paper, we disprove the natural directed…

Combinatorics · Mathematics 2022-01-25 Jacob Fox , Xiaoyu He , Yuval Wigderson

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 2018-09-28 Zhao Wang , Yaping Mao , Colton Magnant , Jinyu Zou

A graph G is Ramsey for H if every two-colouring of the edges of G contains a monochromatic copy of H. Two graphs H and H' are Ramsey-equivalent if every graph G is Ramsey for H if and only if it is Ramsey for H'. In this paper, we study…

Combinatorics · Mathematics 2013-12-03 Jacob Fox , Andrey Grinshpun , Anita Liebenau , Yury Person , Tibor Szabo