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We prove that every properly edge-colored $n$-vertex graph with average degree at least $100(\log n)^2$ contains a rainbow cycle, improving upon $(\log n)^{2+o(1)}$ bound due to Tomon. We also prove that every properly colored $n$-vertex…

组合数学 · 数学 2022-11-08 Jaehoon Kim , Joonkyung Lee , Hong Liu , Tuan Tran

A strong edge-coloring $\varphi$ of a graph $G$ assigns colors to edges of $G$ such that $\varphi(e_1)\ne \varphi(e_2)$ whenever $e_1$ and $e_2$ are at distance no more than 1. It is equivalent to a proper vertex coloring of the square of…

组合数学 · 数学 2022-12-06 Daniel W. Cranston

We show that for any integer $t\geq 2$, every properly edge-coloured graph on $n$ vertices with more than $n^{1+o(1)}$ edges contains a rainbow subdivision of $K_t$. Note that this bound on the number of edges is sharp up to the $o(1)$…

组合数学 · 数学 2023-01-10 Tao Jiang , Abhishek Methuku , Liana Yepremyan

We call an edge-colored graph rainbow if all of its edges receive distinct colors. An edge-colored graph $\Gamma$ is called $H$-rainbow saturated if $\Gamma$ does not contain a rainbow copy of $H$ and adding an edge of any color to $\Gamma$…

组合数学 · 数学 2024-03-20 Debsoumya Chakraborti , Kevin Hendrey , Ben Lund , Casey Tompkins

We use Menger's Theorem and K\"onig's Line Colouring Theorem to show that in any tripartite graph with two complete (bipartite) sides the maximum number of pairwise edge-disjoint triangles equals the minimum number of edges that meet all…

组合数学 · 数学 2023-07-19 Naivedya Amarnani , Amaury De Burgos , Wayne Broughton

Ryser's conjecture says that for every $r$-partite hypergraph $H$ with matching number $\nu(H)$, the vertex cover number is at most $(r-1)\nu(H)$. This far reaching generalization of K\"onig's theorem is only known to be true for $r\leq 3$,…

组合数学 · 数学 2021-11-05 Louis DeBiasio , Yigal Kamel , Grace McCourt , Hannah Sheats

A path in an edge-colored graph is said to be rainbow if no color repeats on it. An edge-colored graph is said to be rainbow $k$-connected if every pair of vertices is connected by $k$ internally disjoint rainbow paths. The rainbow…

组合数学 · 数学 2025-11-19 Igor Araujo , Kareem Benaissa , Richard Bi , Sean English , Shengan Wu , Pai Zheng

A classical result of Corr\'adi and Hajnal states that every graph $G$ on $n$ vertices with $n\in 3\mathbb{N}$ and $\delta(G) \ge 2n/3$ contains a perfect triangle-tiling, i.e.,\ a spanning set of vertex-disjoint triangles. We explore a…

组合数学 · 数学 2024-08-21 Allan Lo , Ella Williams

For a given graph $H$ and $n\geq 1$, let $f(n,H)$ denote the maximum number $c$ for which there is a way to color the edges of the complete graph $K_n$ with $c$ colors such that every subgraph $H$ of $K_n$ has at least two edges of the same…

组合数学 · 数学 2007-05-23 He Chen , Xueliang Li , Jianhua Tu

We prove that if $H$ is a subgraph of a complete multipartite graph $G$, then $H$ contains a connected component $H'$ satisfying $|E(H')||E(G)|\geq |E(H)|^2$. We use this to prove that every three-coloring of the edges of a complete graph…

组合数学 · 数学 2022-08-30 Sammy Luo

In a graph $G$ with a given edge colouring, a rainbow path is a path all of whose edges have distinct colours. The minimum number of colours required to colour the edges of $G$ so that every pair of vertices is joined by at least one…

组合数学 · 数学 2012-12-10 Annika Heckel , Oliver Riordan

Let $G$ be an edge-colored graph on $n$ vertices. The minimum color degree of $G$, denoted by $\delta^c(G)$, is defined as the minimum number of colors assigned to the edges incident to a vertex in $G$. In 2013, H. Li proved that an…

组合数学 · 数学 2025-10-16 Xueliang Li , Bo Ning , Yongtang Shi , Shenggui Zhang

We prove a vertex domination conjecture of Erd\H os, Faudree, Gould, Gy\'arf\'as, Rousseau, and Schelp, that for every n-vertex complete graph with edges coloured using three colours there exists a set of at most three vertices which have…

组合数学 · 数学 2014-02-28 Rahil Baber , John Talbot

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

We prove that every family of (not necessarily distinct) even cycles $D_1, \dotsc, D_{\lfloor 1.2(n-1) \rfloor+1}$ on some fixed $n$-vertex set has a rainbow even cycle (that is, a set of edges from distinct $D_i$'s, forming an even cycle).…

组合数学 · 数学 2024-04-30 Zichao Dong , Zijian Xu

We prove several results on approximate decompositions of edge-coloured quasirandom graphs into rainbow spanning structures. More precisely, we say that an edge-colouring of a graph is locally $\ell$-bounded if no vertex is incident to more…

组合数学 · 数学 2019-10-01 Jaehoon Kim , Daniela Kühn , Andrey Kupavskii , Deryk Osthus

Let $n$ be a sufficiently large integer with $n\equiv 0\pmod 4$ and let $F_i \subseteq{[n]\choose 4}$ where $i\in [n/4]$. We show that if each vertex of $F_i$ is contained in more than ${n-1\choose 3}-{3n/4\choose 3}$ edges, then $\{F_1,…

组合数学 · 数学 2021-05-19 Hongliang Lu , Yan Wang , Xingxing Yu

An edge-colored graph $G$, where adjacent edges may have the same color, is {\it rainbow connected} if every two vertices of $G$ are connected by a path whose edge has distinct colors. A graph $G$ is {\it $k$-rainbow connected} if one can…

组合数学 · 数学 2012-03-15 Hengzhe Li , Xueliang Li , Yuefang Sun , Yan Zhao

Let $G$ be a connected multigraph with $n$ vertices, and suppose $G$ has been edge-colored with $n-1$ colors so that each color class induces a spanning tree. Rota's Basis Conjecture for graphic matroids posits that one can find $n-1$…

组合数学 · 数学 2023-11-02 Anant Asthana , Shreev Goyal

A conjecture due to the fourth author states that every $d$-regular planar multigraph can be $d$-edge-coloured, provided that for every odd set $X$ of vertices, there are at least $d$ edges between $X$ and its complement. For $d = 3$ this…

离散数学 · 计算机科学 2012-10-30 Maria Chudnovsky , Katherine Edwards , Ken-ichi Kawarabayashi , Paul Seymour