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A subgraph of an edge-coloured complete graph is called rainbow if all its edges have different colours. In 1980 Hahn conjectured that every properly edge-coloured complete graph $K_n$ has a rainbow Hamiltonian path. Although this…

组合数学 · 数学 2016-08-26 Noga Alon , Alexey Pokrovskiy , Benny Sudakov

Given graphs $G_1,\ldots,G_s$ all on the same vertex set and a graph $H$ with $e(H) \leq s$, a copy of $H$ is transversal or rainbow if it contains at most one edge from each $G_c$. When $s=e(H)$, such a copy contains exactly one edge from…

组合数学 · 数学 2023-06-07 Yangyang Cheng , Katherine Staden

An $r$-uniform hypergraph ($r$-graph for short) is called linear if every pair of vertices belong to at most one edge. A linear $r$-graph is complete if every pair of vertices are in exactly one edge. The famous Brown-Erd\H{o}s-S\'os…

组合数学 · 数学 2021-09-17 Asaf Shapira , Mykhaylo Tyomkyn

If $G$ is a graph and $\mathcal{H}$ is a set of subgraphs of $G$, we say that an edge-coloring of $G$ is $\mathcal{H}$-polychromatic if every graph from $\mathcal{H}$ gets all colors present in $G$ on its edges. The…

组合数学 · 数学 2020-09-21 John Goldwasser , Ryan Hansen

A sunflower is a collection of distinct sets such that the intersection of any two of them is the same as the common intersection $C$ of all of them, and $|C|$ is smaller than each of the sets. A longstanding conjecture due to Erd\H{o}s and…

组合数学 · 数学 2025-01-29 Dhruv Mubayi , Lujia Wang

A subgraph of an edge-coloured complete graph is called rainbow if all its edges have different colours. The study of rainbow decompositions has a long history, going back to the work of Euler on Latin squares. In this paper we discuss…

组合数学 · 数学 2018-03-20 Alexey Pokrovskiy , Benny Sudakov

Let $G_1,...,G_n$ be graphs on the same vertex set of size $n$, each graph with minimum degree $\delta(G_i)\ge n/2$. A recent conjecture of Aharoni asserts that there exists a rainbow Hamiltonian cycle i.e. a cycle with edge set…

组合数学 · 数学 2021-02-23 Yangyang Cheng , Guanghui Wang , Yi Zhao

A rainbow matching for (not necessarily distinct) sets F_1,...,F_k of hypergraph edges is a matching consisting of k edges, one from each F_i. The aim of the paper is twofold - to put order in the multitude of conjectures that relate to…

组合数学 · 数学 2013-05-28 Ron Aharoni , Pierre Charbit , David Howard

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 and has been the focus of extensive…

组合数学 · 数学 2019-04-24 Richard Montgomery , Alexey Pokrovskiy , Benny Sudakov

Let $G = (G_1, G_2, \ldots, G_m)$ be a collection of $m$ graphs on a common vertex set $V$. For a graph $H$ with vertices in $V$, we say that $G$ contains a rainbow $H$ if there is an injection $c: E(H) \to [m]$ such that for every edge $e…

组合数学 · 数学 2025-12-16 Yupei Li , Ruth Luo

An edge-colored graph is a graph in which each edge is assigned a color. Such a graph is called strongly edge-colored if each color class forms an induced matching, and called rainbow if all edges receive pairwise distinct colors. In this…

组合数学 · 数学 2026-01-23 Laihao Ding , Xiaolan Hu , Suyun Jiang

Let $H_1$ and $H_2$ be graphs. A graph $G$ has the constrained Ramsey property for $(H_1,H_2)$ if every edge-colouring of $G$ contains either a monochromatic copy of $H_1$ or a rainbow copy of $H_2$. Our main result gives a 0-statement for…

组合数学 · 数学 2025-03-27 Natalie Behague , Robert Hancock , Joseph Hyde , Shoham Letzter , Natasha Morrison

For any $r$-graph $H$, we consider the problem of finding a rainbow $H$-factor in an $r$-graph $G$ with large minimum $\ell$-degree and an edge-colouring that is suitably bounded. We show that the asymptotic degree threshold is the same as…

组合数学 · 数学 2018-03-29 Matthew Coulson , Peter Keevash , Guillem Perarnau , Liana Yepremyan

Given an edge-colored graph $G$, we denote the number of colors as $c(G)$, and the number of edges as $e(G)$. An edge-colored graph is rainbow if no two edges share the same color. A proper $mK_3$ is a vertex disjoint union of $m$ rainbow…

组合数学 · 数学 2024-02-29 Jürgen Kritschgau , tahda queer , Cyrus Young , Wohua Zhou

A harmonious coloring of a $k$-uniform hypergraph $H$ is a vertex coloring such that no two vertices in the same edge have the same color, and each $k$-element subset of colors appears on at most one edge. The harmonious number $h(H)$ is…

组合数学 · 数学 2024-08-07 Sebastian Czerwiński

Erd\H{o}s and Szekeres's quantitative version of Ramsey's theorem asserts that any complete graph on n vertices that is edge-colored with two colors has a monochromatic clique on at least 1/2log(n) vertices. The famous Erd\H{o}s-Hajnal…

组合数学 · 数学 2021-07-30 Maria Axenovich , Richard Snyder , Lea Weber

Given a graph $H$, let $g(n,H)$ denote the smallest $k$ for which the following holds. We can assign a $k$-colouring $f_v$ of the edge set of $K_n$ to each vertex $v$ in $K_n$ with the property that for any copy $T$ of $H$ in $K_n$, there…

组合数学 · 数学 2023-04-25 Barnabás Janzer , Oliver Janzer

We consider coloring problems inspired by the theory of anti-Ramsey / rainbow colorings that we generalize to a far extent. Let $\mathcal{F}$ be a hereditary family of graphs; i.e., if $H\in \mathcal{F}$ and $H'\subset H$ then also…

组合数学 · 数学 2024-12-17 Yair Caro , Zsolt Tuza

A first-order structure $M$ is said to have the infinite sunflower property if, for each $k \in \mathbb{N}_+$ and each structure $M' \cong M$ whose elements are $k$-sets, there is $S \subseteq M'$, $S \cong M$, such that $S$ is a sunflower:…

组合数学 · 数学 2026-03-10 Rob Sullivan , Jeroen Winkel

A subgraph $H$ of an edge-coloured graph is called rainbow if all of the edges of $H$ have different colours. In 1989, Andersen conjectured that every proper edge-colouring of $K_{n}$ admits a rainbow path of length $n-2$. We show that…

组合数学 · 数学 2022-04-22 Stephen Gould , Tom Kelly , Daniela Kühn , Deryk Osthus