Recent Progress in Ramsey Theory

Fuente: arXiv
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Main Author: Verstraete, Jacques
Format: Preprint
Published: 2025
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author Verstraete, Jacques
author_facet Verstraete, Jacques
contents The classical Ramsey numbers $r(s,t)$ denote the minimum $n$ such that every red-blue coloring of the edges of the complete graph $K_n$ contains either a red clique of order $s$ or a blue clique of order $t$. These quantities are the centerpiece of graph Ramsey Theory, and have been studied for almost a century. The Erdős-Szekeres Theorem (1935) shows that for each $s \geq 2$, $r(s,t) = O(t^{s - 1})$ as $t \rightarrow \infty$. We introduce a new approach using pseudorandom graphs which shows $r(4,t) = Ω(t^3/(\log t)^4)$ as $t \rightarrow \infty$, answering an old conjecture of Erdős, and we illustrate how to apply this approach to many other Ramsey and related combinatorial problems.
format Preprint
id arxiv_https___arxiv_org_abs_2503_22094
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Recent Progress in Ramsey Theory
Verstraete, Jacques
Combinatorics
05C
The classical Ramsey numbers $r(s,t)$ denote the minimum $n$ such that every red-blue coloring of the edges of the complete graph $K_n$ contains either a red clique of order $s$ or a blue clique of order $t$. These quantities are the centerpiece of graph Ramsey Theory, and have been studied for almost a century. The Erdős-Szekeres Theorem (1935) shows that for each $s \geq 2$, $r(s,t) = O(t^{s - 1})$ as $t \rightarrow \infty$. We introduce a new approach using pseudorandom graphs which shows $r(4,t) = Ω(t^3/(\log t)^4)$ as $t \rightarrow \infty$, answering an old conjecture of Erdős, and we illustrate how to apply this approach to many other Ramsey and related combinatorial problems.
title Recent Progress in Ramsey Theory
topic Combinatorics
05C
url https://arxiv.org/abs/2503.22094