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Consider the set $[m]\times [n] = \{(i,j)\, : 1\le i \le m, 1\le j \le n\}$ and the equation $x_1+x_2 = x_3$, namely $eq$. The \emph{rainbow number of $[m] \times [n]$ for $eq$}, denoted $\text{rb}([m]\times [n],eq)$, is the smallest number…

Combinatorics · Mathematics 2023-01-26 Kean Fallon , Ethan Manhart , Joe Miller , Hunter Rehm , Nathan Warnberg , Laura Zinnel

A rainbow colouring of a connected graph is a colouring of the edges of the graph, such that every pair of vertices is connected by at least one path in which no two edges are coloured the same. Such a colouring using minimum possible…

Discrete Mathematics · Computer Science 2012-05-09 L. Sunil Chandran , Deepak Rajendraprasad

An edge-colored graph $G$ is called rainbow if every edge of $G$ receives a different color. The anti-Ramsey number of $t$ edge-disjoint rainbow spanning trees, denoted by $r(n,t)$, is defined as the maximum number of colors in an…

Combinatorics · Mathematics 2019-11-19 Linyuan Lu , Zhiyu Wang

In this work, we investigate the fewest number of colors needed to guarantee a rainbow solution to the equation $x_1 + x_2 = k x_3$ in $\mathbb{Z}_n$. This value is called the Rainbow number and is denoted by $rb(\mathbb{Z}_n, k)$ for…

Combinatorics · Mathematics 2018-09-13 Erin Bevilacqua , Samuel King , Jürgen Kritschgau , Michael Tait , Suzannah Tebon , Michael Young

The Rainbow k-Coloring problem asks whether the edges of a given graph can be colored in $k$ colors so that every pair of vertices is connected by a rainbow path, i.e., a path with all edges of different colors. Our main result states that…

Data Structures and Algorithms · Computer Science 2016-02-19 Łukasz Kowalik , Juho Lauri , Arkadiusz Socała

The anti-Ramsey number, $ar(G, H)$ is the minimum integer $k$ such that in any edge colouring of $G$ with $k$ colours there is a rainbow subgraph isomorphic to $H$, i.e., a copy of $H$ with each of its edges assigned a different colour. The…

Discrete Mathematics · Computer Science 2019-10-28 L Sunil Chandran , Abhiruk Lahiri , Nitin Singh

Let the integers $1,\ldots,n$ be assigned colors. Szemer\'edi's theorem implies that if there is a dense color class then there is an arithmetic progression of length three in that color. We study the conditions on the color classes forcing…

Combinatorics · Mathematics 2016-05-25 Maria Axenovich , Ryan R. Martin

An exact r-coloring of a set $S$ is a surjective function $c:S \rightarrow \{1, 2, \ldots,r\}$. A rainbow solution to an equation over $S$ is a solution such that all components are a different color. We prove that every 3-coloring of…

Combinatorics · Mathematics 2023-05-25 Katie Ansaldi , Gabriel Cowley , Eric Green , Kihyun Kim , JT Rapp

We study an analogue of the Ramsey multiplicity problem for additive structures, in particular establishing the minimum number of monochromatic 3-APs in 3-colorings of $\mathbb{F}_3^n$ as well as obtaining the first non-trivial lower bound…

Combinatorics · Mathematics 2023-04-04 Juanjo Rué , Christoph Spiegel

An edge-colored graph $G$ is said to be rainbow connected if between each pair of vertices there exists a path which uses each color at most once. The rainbow connection number, denoted by $rc(G)$, is the minimum number of colors needed to…

Discrete Mathematics · Computer Science 2015-10-14 Eduard Eiben , Robert Ganian , Juho Lauri

For $n \geq k \geq 4$, let $AR_{X + Y = Z + T}^k (n)$ be the maximum number of rainbow solutions to the Sidon equation $X+Y = Z + T$ over all $k$-colorings $c:[n] \rightarrow [k]$. It can be shown that the total number of solutions in $[n]$…

Combinatorics · Mathematics 2018-08-30 Vladislav Taranchuk , Craig Timmons

Let $K\_{[k,t]}$ be the complete graph on $k$ vertices from which a set of edges, induced by a clique of order $t$, has been dropped. In this note we give two explicit upper bounds for $R(K\_{[k\_1,t\_1]},\dots, K\_{[k\_r,t\_r]})$ (the…

Combinatorics · Mathematics 2014-12-15 Jonathan Chappelon , Luis Pedro Montejano , Jorge Luis Ramírez Alfonsín

A well-known result by Graham in Euclidean Ramsey Theory states that, for every positive real number $A$, every coloring of the plane with finite number of colors contains a monochromatic triangle of area $A$. We consider canonical versions…

Combinatorics · Mathematics 2026-03-17 Sukumar Das Adhikari , Tássio Naia , Oriol Serra

For a set of positive integers $A \subseteq [n]$, an $r$-coloring of $A$ is rainbow sum-free if it contains no rainbow Schur triple. In this paper we initiate the study of the rainbow Erd\H{o}s-Rothchild problem in the context of sum-free…

Combinatorics · Mathematics 2023-04-05 Yangyang Cheng , Yifan Jing , Lina Li , Guanghui Wang , Wenling Zhou

Given two graphs $G$ and $H$, the {\it rainbow number} $rb(G,H)$ for $H$ with respect to $G$ is defined as the minimum number $k$ such that any $k$-edge-coloring of $G$ contains a rainbow $H$, i.e., a copy of $H$, all of whose edges have…

Combinatorics · Mathematics 2018-09-27 Zhongmei Qin , Yongxin Lan , Yongtang Shi

We give an exponential improvement to the lower bound on diagonal Ramsey numbers for any fixed number of colors greater than two.

Combinatorics · Mathematics 2020-11-30 David Conlon , Asaf Ferber

An exact $r$-coloring of a set $S$ is a surjective function $c:S\to [r]$. The rainbow number of a set $S$ for equation $eq$ is the smallest integer $r$ such that every exact $r$-coloring of $S$ contains a rainbow solution to $eq$. In this…

Combinatorics · Mathematics 2019-11-26 Katie Ansaldi , Houssein El Turkey , Jessica Hamm , Anisah Nu'Man , Nathan Warnberg , Michael Young

For positive integers $n,r,s$ with $r > s$, the set-coloring Ramsey number $R(n;r,s)$ is the minimum $N$ such that if every edge of the complete graph $K_N$ receives a set of $s$ colors from a palette of $r$ colors, then there is guaranteed…

Combinatorics · Mathematics 2022-06-24 David Conlon , Jacob Fox , Xiaoyu He , Dhruv Mubayi , Andrew Suk , Jacques Verstraete

The $r$-colour Ramsey number $R_r(k)$ is the minimum $n \in \mathbb{N}$ such that every $r$-colouring of the edges of the complete graph $K_n$ on $n$ vertices contains a monochromatic copy of $K_k$. We prove, for each fixed $r \geqslant 2$,…

We consider the rainbow Schur number $RS_m(n)$, defined to be the minimum number of colors such that every coloring of $\{1,2,\ldots,n\}$, using all $RS_m(n)$ colors, contains a rainbow solution to the equation $x_1+x_2+\cdots…

Combinatorics · Mathematics 2024-01-17 Mark Budden , Bruce Landman