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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

We show that the Ramsey number is linear for every uniform hypergraph with bounded-degree. This is a hypergraph extension of the famous theorem for ordinary graphs which Chv\'atal et al. showed in 1983. Our proof is simple, contains the…

Combinatorics · Mathematics 2007-12-14 Yoshiyasu Ishigami

We show that for every finite colouring of the natural numbers there exists $a,b >1$ such that the triple $\{a,b,a^b\}$ is monochromatic. We go on to show the partition regularity of a much richer class of patterns involving exponentiation.…

Combinatorics · Mathematics 2016-10-24 Julian Sahasrabudhe

It is observed that the conjugacy growth series of the infinite finitary symmetric group with respect to the generating set of transpositions is the generating series of the partition function. Other conjugacy growth series are computed,…

Combinatorics · Mathematics 2016-03-18 Roland Bacher

Let $K_m^{(3)}$ denote the complete $3$-uniform hypergraph on $m$ vertices and $S_n^{(3)}$ the $3$-uniform hypergraph on $n+1$ vertices consisting of all $\binom{n}{2}$ edges incident to a given vertex. Whereas many hypergraph Ramsey…

Combinatorics · Mathematics 2022-10-10 David Conlon , Jacob Fox , Xiaoyu He , Dhruv Mubayi , Andrew Suk , Jacques Verstraete

We show that the big Ramsey degrees of every countable universal $u$-uniform $\omega$-edge-labeled hypergraph are infinite for every $u\geq 2$. Together with a recent result of Braunfeld, Chodounsk\'y, de Rancourt, Hubi\v{c}ka, Kawach, and…

Combinatorics · Mathematics 2025-10-01 Jan Hubička , Matěj Konečný , Stevo Todorcevic , Andy Zucker

We show that there is an absolute constant $c>0$ such that the following holds. For every $n > 1$, there is a 5-uniform hypergraph on at least $2^{2^{cn^{1/4}}}$ vertices with independence number at most $n$, where every set of 6 vertices…

Combinatorics · Mathematics 2020-03-03 Dhruv Mubayi , Andrew Suk , Emily Zhu

For a $k$-uniform hypergraph $F$ and a positive integer $n$, the Ramsey number $r(F,n)$ denotes the minimum $N$ such that every $N$-vertex $F$-free $k$-uniform hypergraph contains an independent set of $n$ vertices. A hypergraph is…

Combinatorics · Mathematics 2024-09-04 Sam Mattheus , Dhruv Mubayi , Jiaxi Nie , Jacques Verstraëte

We introduce the list colouring extension of classical Ramsey numbers. We investigate when the two Ramsey numbers are equal, and in general, how far apart they can be from each other. We find graph sequences where the two are equal and…

Combinatorics · Mathematics 2020-08-13 N. Alon , M. Bucić , T. Kalvari , E. Kuperwasser , T. Szabó

We give a characterizations of Ramsey ultrafilters on $\mathscr P(\omega)$ in terms of functions $f:\omega^n\to\omega$ and their ultrafilter extensions. To do this, we prove that for any partition $\mathcal P$ of $[\omega]^n$ there is a…

Logic · Mathematics 2022-03-25 N. L. Polyakov

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

We give an exponential improvement to the lower bound on diagonal Ramsey numbers for any fixed number of colors greater than two.

Combinatorics · Mathematics 2020-11-30 David Conlon , Asaf Ferber

We prove a Ramsey theorem for finite sets equipped with a partial order and a fixed number of linear orders extending the partial order. This is a common generalization of two recent Ramsey theorems due to Soki\'c. As a bonus, our proof…

Combinatorics · Mathematics 2015-02-17 Slawomir Solecki , Min Zhao

We prove that finite partial orders with a linear extension form a Ramsey class. Our proof is based on the fact that class of acyclic graphs has the Ramsey property and uses the partite construction.

Combinatorics · Mathematics 2017-03-03 Jaroslav Nešetřil , Vojtěch Rödl

We estimate Ramsey numbers for bipartite graphs with small bandwidth and bounded maximum degree. In particular we determine asymptotically the two and three color Ramsey numbers for grid graphs. More generally, we determine asymptotically…

Combinatorics · Mathematics 2016-02-22 Guilherme O. Mota , Gábor N. Sárközy , Mathias Schacht , Anusch Taraz

A natural open problem in Ramsey theory is to determine those $3$-graphs $H$ for which the off-diagonal Ramsey number $r(H, K_n^{(3)})$ grows polynomially with $n$. We make substantial progress on this question by showing that if $H$ is…

Chvatal, Roedl, Szemeredi and Trotter proved that the Ramsey numbers of graphs of bounded maximum degree are linear in their order. In previous work, we proved the same result for 3-uniform hypergraphs. Here we extend this result to…

Combinatorics · Mathematics 2008-06-19 Oliver Cooley , Nikolaos Fountoulakis , Daniela Kühn , Deryk Osthus

Ramsey theory is a central and active branch of combinatorics. Although Ramsey numbers for graphs have been extensively investigated since Ramsey's work in the 1930s, there is still an exponential gap between the best known lower and upper…

Combinatorics · Mathematics 2025-01-03 António Girão , Gal Kronenberg , Alex Scott

For a $k$-uniform hypergraph $G$ with vertex set $\{1,\ldots,n\}$, the ordered Ramsey number $\operatorname{OR}_t(G)$ is the least integer $N$ such that every $t$-coloring of the edges of the complete $k$-uniform graph on vertex set…

Combinatorics · Mathematics 2014-12-05 Christopher Cox , Derrick Stolee

In Euclidean Ramsey Theory usually we are looking for monochromatic configurations in the Euclidean space, whose points are colored with a fixed number of colors. In the canonical version, the number of colors is arbitrary, and we are…

Combinatorics · Mathematics 2026-02-03 Panna Gehér , Arsenii Sagdeev , Géza Tóth
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