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A subgraph of an edge-coloured graph is called rainbow if all its edges have different colours. We prove a rainbow version of the blow-up lemma of Koml\'os, S\'ark\"ozy and Szemer\'edi that applies to almost optimally bounded colourings. A…

组合数学 · 数学 2019-07-24 Stefan Ehard , Stefan Glock , Felix Joos

The anti-Ramsey number $\mathrm{ar}(n,F)$ of an $r$-graph $F$ is the minimum number of colors needed to color the complete $n$-vertex $r$-graph to ensure the existence of a rainbow copy of $F$. We establish a removal-type result for the…

组合数学 · 数学 2024-10-15 Xizhi Liu , Jialei Song

A meta-conjecture of Coulson, Keevash, Perarnau and Yepremyan states that above the extremal threshold for a given spanning structure in a (hyper-)graph, one can find a rainbow version of that spanning structure in any suitably bounded…

组合数学 · 数学 2026-02-25 Amarja Kathapurkar , Patrick Morris , Guillem Perarnau

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…

逻辑 · 数学 2018-12-18 Jeffrey Bergfalk , Michael Hrušák , Saharon Shelah

A hypergraph $H$ is properly colored if for every vertex $v\in V(H)$, all the edges incident to $v$ have distinct colors. In this paper, we show that if $H_{1}$, \cdots, $H_{s}$ are properly-colored $k$-uniform hypergraphs on $n$ vertices,…

组合数学 · 数学 2018-08-16 Hao Huang , Tong Li , Guanghui Wang

A properly edge-colored graph is a graph with a coloring of its edges such that no vertex is incident to two or more edges of the same color. A subgraph is called rainbow if all its edges have different colors. The problem of finding…

组合数学 · 数学 2024-12-19 Benny Sudakov

For a fixed graph $H$ on $k$ vertices, and a graph $G$ on at least $k$ vertices, we write $G\rightarrow H$ if in any vertex-coloring of $G$ with $k$ colors, there is an induced subgraph isomorphic to $H$ whose vertices have distinct colors.…

组合数学 · 数学 2016-05-23 Maria Axenovich , Ryan Martin

An edge-colouring of a graph $G$ can fail to be rainbow for two reasons: either it contains a monochromatic cherry (a pair of incident edges), or a monochromatic matching of size two. A colouring is a proper colouring if it forbids the…

组合数学 · 数学 2025-11-18 Allan Lo , Klas Markström , Dhruv Mubayi , Katherine Staden , Maya Stein , Lea Weber

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

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

Let $H$ be an edge colored hypergraph. We say that $H$ contains a \emph{rainbow} copy of a hypergraph $S$ if it contains an isomorphic copy of $S$ with all edges of distinct colors. We consider the following setting. A randomly edge colored…

组合数学 · 数学 2015-06-10 Asaf Ferber , Michael Krivelevich

We study the following rainbow version of subgraph containment problems in a family of (hyper)graphs, which generalizes the classical subgraph containment problems in a single host graph. For a collection $\textbf{G}=\{G_1, G_2,\ldots,…

组合数学 · 数学 2023-10-05 Yangyang Cheng , Jie Han , Bin Wang , Guanghui Wang

Sunflowers, or $\Delta$-systems, are a fundamental concept in combinatorics introduced by Erd\H{o}s and Rado in their paper: {\em Intersection theorems for systems of sets}, J. Lond. Math. Soc. (1) {\bf 35} (1960), 85--90. A sunflower is a…

组合数学 · 数学 2025-09-19 Anup Rao

The Ramsey multiplicity constant of a graph $H$ is the minimum proportion of copies of $H$ in the complete graph which are monochromatic under an edge-coloring of $K_n$ as $n$ goes to infinity. Graphs for which this minimum is…

组合数学 · 数学 2018-03-29 Jessica De Silva , Xiang Si , Michael Tait , Yunus Tunçbilek , Ruifan Yang , Michael Young

Extremal problems on set systems with restricted intersections have been an important part of combinatorics in the last 70 year. In this paper, we study the following Ramsey version of these problems. Given a set $L\subseteq…

组合数学 · 数学 2025-04-22 Barnabás Janzer , Zhihan Jin , Benny Sudakov , Kewen Wu

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…

逻辑 · 数学 2024-11-20 Michael Hrušák , Saharon Shelah , Jing Zhang

For graphs $G$ and $H$, we write $G \overset{\mathrm{rb}}{\longrightarrow} H $ if any proper edge-coloring of $G$ contains a rainbow copy of $H$, i.e., a copy where no color appears more than once. Kohayakawa, Konstadinidis and the last…

A graph $G$ whose edges are coloured (not necessarily properly) contains a full rainbow matching if there is a matching $M$ that contains exactly one edge of each colour. We refute several conjectures on matchings in hypergraphs and full…

组合数学 · 数学 2017-10-16 Pu Gao , Reshma Ramadurai , Ian M. Wanless , Nick Wormald

A subgraph of an edge-coloured graph is called rainbow if all its edges have different colours. The problem of finding rainbow subgraphs goes back to the work of Euler on transversals in Latin squares and was extensively studied since then.…

组合数学 · 数学 2017-11-13 Frederik Benzing , Alexey Pokrovskiy , Benny Sudakov

A subgraph of an edge-coloured graph is called rainbow if all its edges have distinct colours. The study of rainbow subgraphs goes back more than two hundred years to the work of Euler on Latin squares. Since then rainbow structures have…

组合数学 · 数学 2018-12-11 Richard Montgomery , Alexey Pokrovskiy , Benny Sudakov
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