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A colored complete graph is said to be Gallai-colored if it contains no rainbow triangle. This property has been shown to be equivalent to the existence of a partition of the vertices (of every induced subgraph) in which at most two colors…

组合数学 · 数学 2019-05-29 Colton Magnant , Zhuojun Magnant

When many colors appear in edge-colored graphs, it is only natural to expect rainbow subgraphs to appear. This anti-Ramsey problem has been studied thoroughly and yet there remain many gaps in the literature. Expanding upon classical and…

组合数学 · 数学 2019-05-30 Chuandong Xu , Colton Magnant , Shenggui Zhang

Given an $r$-edge-coloring of the complete graph $K_n$, what is the largest number of edges in a monochromatic connected component? This natural question has only recently received the attention it deserves, with work by two disjoint…

组合数学 · 数学 2022-09-02 David Conlon , Sammy Luo , Mykhaylo Tyomkyn

Given an edge colouring of a graph with a set of $m$ colours, we say that the graph is (exactly) $m$-coloured if each of the colours is used. We consider edge colourings of the complete graph on $\mathbb{N}$ with infinitely many colours and…

组合数学 · 数学 2016-09-07 Teeradej Kittipassorn , Bhargav Narayanan

Extending an earlier conjecture of Erd\H{o}s, Burr and Rosta conjectured that among all two-colorings of the edges of a complete graph, the uniformly random coloring asymptotically minimizes the number of monochromatic copies of any fixed…

组合数学 · 数学 2023-06-28 Jacob Fox , Yuval Wigderson

We estimate the $3$-colour bipartite Ramsey number for balanced bipartite graphs $H$ with small bandwidth and bounded maximum degree. More precisely, we show that the minimum value of $N$ such that in any $3$-edge colouring of $K_{N,N}$…

组合数学 · 数学 2018-04-10 Guilherme Oliveira Mota

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…

组合数学 · 数学 2026-02-03 Panna Gehér , Arsenii Sagdeev , Géza Tóth

We consider following geometric Ramsey problem: find the least dimension $n$ such that for any 2-coloring of edges of complete graph on the points $\{\pm 1\}^n$ there exists 4-vertex coplanar monochromatic clique. Problem was first analyzed…

组合数学 · 数学 2020-04-14 Eryk Lipka

Answering a question raised by Dudek and Pra\l{}at, we show that if $pn\rightarrow \infty$, w.h.p.,~whenever $G=G(n,p)$ is $2$-coloured, there exists a monochromatic path of length $n(2/3+o(1))$. This result is optimal in the sense that…

组合数学 · 数学 2019-02-20 Shoham Letzter

Conventional Ramsey-theoretic investigations for edge-colourings of complete graphs are framed around avoidance of certain configurations. Motivated by considerations arising in the field of Qualitative Reasoning, we explore edge colourings…

组合数学 · 数学 2022-01-11 Badriah Al Juaid , Marcel Jackson , James Koussas , Tomasz Kowalski

The Ramsey multiplicity problem asks for the minimum asymptotic density of monochromatic labelled copies of a graph $H$ in a red/blue colouring of the edges of $K_n$. We introduce an off-diagonal generalization in which the goal is to…

组合数学 · 数学 2023-07-03 Elena Moss , Jonathan A. Noel

This paper introduces a general methodology, based on abstraction and symmetry, that applies to solve hard graph edge-coloring problems and demonstrates its use to provide further evidence that the Ramsey number $R(4,3,3)=30$. The number…

人工智能 · 计算机科学 2015-03-27 Michael Codish , Michael Frank , Avraham Itzhakov , Alice Miller

A matching $M$ in a graph $G$ is connected if all the edges of $M$ are in the same component of $G$. Following \L uczak,there have been many results using the existence of large connected matchings in cluster graphs with respect to regular…

组合数学 · 数学 2021-10-14 József Balogh , Alexandr Kostochka , Mikhail Lavrov , Xujun Liu

One of the toughest problems in Ramsey theory is to determine the existence of monochromatic arithmetic progressions in groups whose elements have been colored. We study the harder problem to not only determine the existence of…

组合数学 · 数学 2014-11-11 Erik Sjöland

In an $r$-coloring of edges of the complete graph on $n$ vertices, how many edges are there in the largest monochromatic connected component? A construction of Gy\'arf\'as shows that for infinitely many values of $r$, there exist colorings…

组合数学 · 数学 2026-02-18 Hannah Fox , Sammy Luo

Let $R(C_n)$ be the Ramsey number of the cycle on $n$ vertices. We prove that, for some $C > 0$, with high probability every $2$-colouring of the edges of $G(N,p)$ has a monochromatic copy of $C_n$, as long as $N\geq R(C_n) + C/p$ and $p…

组合数学 · 数学 2024-08-22 Pedro Araújo , Matías Pavez-Signé , Nicolás Sanhueza-Matamala

An edge coloring of the $n$-vertex complete graph, $K_n$, is a Gallai coloring if it does not contain any rainbow triangle, that is, a triangle whose edges are colored with three distinct colors. We prove that for $n$ large and every $k$…

组合数学 · 数学 2018-12-31 Josefran de Oliveira Bastos , Fabricio S. Benevides , Jie Han

We consider $m$-colorings of the edges of a complete graph, where each color class is defined semi-algebraically with bounded complexity. The case $m = 2$ was first studied by Alon et al., who applied this framework to obtain surprisingly…

组合数学 · 数学 2018-12-07 Jacob Fox , Janos Pach , Andrew Suk

We extend two well-known results in Ramsey theory from from $K_n$ to arbitrary $n$-chromatic graphs. The first is a note of Erd\H os and Rado stating that in every 2-coloring of the edges of $K_n$ there is a monochromatic tree on $n$…

组合数学 · 数学 2015-06-16 Arie Bialostocki , Andras Gyarfas

The generalized Ramsey number $r(G, H, q)$ is the minimum number of colors needed to color the edges of $G$ such that every isomorphic copy of $H$ has at least $q$ colors. In this note, we improve the upper and lower bounds on $r(K_{n, n},…

组合数学 · 数学 2025-07-18 Deepak Bal , Patrick Bennett