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Chudnovsky, Kim, Oum, and Seymour recently established that any prime graph contains one of a short list of induced prime subgraphs [1]. In the present paper we reprove their theorem using many of the same ideas, but with the key…

Logic · Mathematics 2015-11-10 M. Malliaris , C. Terry

We prove that hypergraphs defined by low-degree polynomial inequalities contain large homogeneous subsets. Formally, let $H$ be an $r$-uniform hypergraph on $N$ vertices that is semialgebraic of constant description complexity, and each…

Combinatorics · Mathematics 2026-02-23 Azem Adibelli , István Tomon

Aboulker, Adler, Kim, Sintiari, and Trotignon conjectured that every graph with bounded maximum degree and large treewidth must contain, as an induced subgraph, a large subdivided wall, or the line graph of a large subdivided wall. This…

Combinatorics · Mathematics 2022-05-19 Bogdan Alecu , Maria Chudnovsky , Kristina Vušković

A graph on $n$ vertices is said to be \emph{$C$-Ramsey} if every clique or independent set of the graph has size at most $C \log n$. The only known constructions of Ramsey graphs are probabilistic in nature, and it is generally believed…

Combinatorics · Mathematics 2017-09-08 Bhargav Narayanan , Julian Sahasrabudhe , István Tomon

An infinite graph is said to be highly connected if the induced subgraph on the complement of any set of vertices of smaller size is connected. We continue the study of weaker versions of Ramsey Theorem on uncountable cardinals asserting…

Logic · Mathematics 2024-11-20 Michael Hrušák , Saharon Shelah , Jing Zhang

Inspired by a width invariant on permutations defined by Guillemot and Marx, Bonnet, Kim, Thomass\'e, and Watrigant introduced the twin-width of graphs, which is a parameter describing its structural complexity. This invariant has been…

Logic in Computer Science · Computer Science 2024-08-07 Édouard Bonnet , Jaroslav Nešetřil , Patrice Ossona de Mendez , Sebastian Siebertz , Stéphan Thomassé

The Ramsey's theorem says that a graph with sufficiently many vertices contains a clique or stable set with many vertices. Now we attach some parameter to every vertex, such as degree. Consider the case a graph with sufficiently many…

Combinatorics · Mathematics 2023-07-18 Jin Sun

In this paper, we investigate the set of sizes of induced subgraphs of bipartite graphs. We introduce the definition of $C$-$Bipartite$-$Ramsey$ graphs, which is closely related to Ramsey graphs and prove that in `most' cases, these graphs…

Combinatorics · Mathematics 2021-09-20 Mantas Baksys , Xuanang Chen

We study two graph parameters defined via tree decompositions: tree-independence number and induced matching treewidth. Both parameters are defined similarly as treewidth, but with respect to different measures of a tree decomposition…

Discrete Mathematics · Computer Science 2025-11-07 Noga Alon , Martin Milanič , Paweł Rzążewski

We prove essentially sharp bounds for Ramsey numbers of ordered hypergraph matchings, inroduced recently by Dudek, Grytczuk, and Ruci\'{n}ski. Namely, for any $r \ge 2$ and $n \ge 2$, we show that any collection $\mathcal H$ of $n$ pairwise…

Combinatorics · Mathematics 2025-07-21 Lisa Sauermann , Dmitrii Zakharov

One of the central questions in Ramsey theory asks how small can be the size of the largest clique and independent set in a graph on $N$ vertices. By the celebrated result of Erd\H{o}s from 1947, the random graph on $N$ vertices with edge…

Combinatorics · Mathematics 2021-03-18 Benny Sudakov , István Tomon

Recently, Alon, Cambie, and Kang introduced asymmetric list coloring of bipartite graphs, where the size of each vertex's list depends on its part. For complete bipartite graphs, we fix the list sizes of one part and consider the resulting…

Combinatorics · Mathematics 2023-08-29 Daniel G. Zhu

An infinite graph is highly connected if the complement of any subgraph of smaller size is connected. We consider weaker versions of Ramsey's Theorem asserting that in any coloring of the edges of a complete graph there exist large highly…

Logic · Mathematics 2018-12-18 Jeffrey Bergfalk , Michael Hrušák , Saharon Shelah

We prove that, for every graph $F$ with at least one edge, there is a constant $c_F$ such that there are graphs of arbitrarily large chromatic number and the same clique number as $F$ in which every $F$-free induced subgraph has chromatic…

An n-vertex graph is called C-Ramsey if it has no clique or independent set of size C log n. All known constructions of Ramsey graphs involve randomness in an essential way, and there is an ongoing line of research towards showing that in…

Combinatorics · Mathematics 2021-09-08 Matthew Kwan , Benny Sudakov

Ramsey's theorem, in the version of Erd\H{o}s and Szekeres, states that every 2-coloring of the edges of the complete graph on {1, 2,...,n} contains a monochromatic clique of order 1/2\log n. In this paper, we consider two well-studied…

Combinatorics · Mathematics 2019-12-19 David Conlon , Jacob Fox , Benny Sudakov

In 1930, Ramsey proved that every infinite graph contains either an infinite clique or an infinite independent set as an induced subgraph. K\"{o}nig proved that every infinite graph contains either a ray or a vertex of infinite degree. In…

Combinatorics · Mathematics 2024-12-06 Sarah Allred , Guoli Ding , Bogdan Oporowski

We investigate Ramsey numbers of bounded degree graphs and provide an interpolation between known results on the Ramsey numbers of general bounded degree graphs and bounded degree graphs of small bandwidth. Our main theorem implies that…

Combinatorics · Mathematics 2015-04-24 Choongbum Lee

Given a function $p : V(G)\to \mathbb N$ and an integer $k\ge 0$, define $p_k(G)$ as the number of vertices with $p(v)\ge k$. We say that $p_k(G)$ is bounded for all $\HH$-free graphs if there exists a constant $c=c(\HH)$ such that…

Combinatorics · Mathematics 2025-12-05 Jin Sun , Xinmin Hou

We show tight necessary and sufficient conditions on the sizes of small bipartite graphs whose union is a larger bipartite graph that has no large bipartite independent set. Our main result is a common generalization of two classical…

Discrete Mathematics · Computer Science 2015-03-03 Chinmoy Dutta , Jaikumar Radhakrishnan