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An independent set in a graph $G$ is a set of pairwise non-adjacent vertices. A tree decomposition of $G$ is a pair $(T, \chi)$ where $T$ is a tree and $\chi : V(T) \rightarrow 2^{V(G)}$ is a function satisfying the following two axioms:…

Combinatorics · Mathematics 2026-05-07 Maria Chudnovsky , Ajaykrishnan E S , Daniel Lokshtanov

Let $G$ be a triangle-free graph with $n$ vertices and average degree $t$. We show that $G$ contains at least \[ e^{(1-n^{-1/12})\frac{1}{2}\frac{n}{t}\ln t (\frac{1}{2}\ln t-1)} \] independent sets. This improves a recent result of the…

Combinatorics · Mathematics 2019-02-20 Jeff Cooper , Kunal Dutta , Dhruv Mubayi

A path in an edge-colored graph is \textit{rainbow} if no two edges of it are colored the same. The graph is said to be \textit{rainbow connected} if there is a rainbow path between every pair of vertices. If there is a rainbow shortest…

Computational Complexity · Computer Science 2016-02-18 Juho Lauri

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 $n-1$…

Combinatorics · Mathematics 2023-11-02 Anant Asthana , Shreev Goyal

Let $G$ be a nontrivial connected graph with an edge-coloring $c:E(G)\rightarrow \{1,2,\ldots,q\},$ $q\in \mathbb{N}$, where adjacent edges may be colored the same. A tree $T$ in $G$ is a $rainbow tree$ if no two edges of $T$ receive the…

Combinatorics · Mathematics 2013-08-21 Xueliang Li , Kang Yang , Yan Zhao

An edge-colored graph is rainbow if all its edges are colored with distinct colors. For a fixed graph $H$, the rainbow Tur\'an number $\mathrm{ex}^{\ast}(n,H)$ is defined as the maximum number of edges in a properly edge-colored graph on…

Combinatorics · Mathematics 2012-05-15 Shagnik Das , Choongbum Lee , Benny Sudakov

Computing the maximum size of an independent set in a graph is a famously hard combinatorial problem that has been well-studied for various classes of graphs. When it comes to random graphs, only the classical Erd\H{o}s-R\'enyi-Gilbert…

Combinatorics · Mathematics 2024-07-17 Akshay Gupte , Yiran Zhu

Given a graph $G=(V,E)$ on $n$ vertices and an assignment of colours to its edges, a set of edges $S \subseteq E$ is said to be rainbow if edges from $S$ have pairwise different colours assigned to them. In this paper, we investigate…

Combinatorics · Mathematics 2023-11-02 Deepak Bal , Alan Frieze , Pawel Pralat

A path in an edge-coloured graph is called \emph{rainbow path} if its edges receive pairwise distinct colours. An edge-coloured graph is said to be \emph{rainbow connected} if any two distinct vertices of the graph are connected by a…

Combinatorics · Mathematics 2019-11-05 Trung Duy Doan , Ingo Schiermeyer

An edge-coloured path is \emph{rainbow} if its edges have distinct colours. An edge-coloured connected graph is said to be \emph{rainbow connected} if any two vertices are connected by a rainbow path, and \emph{strongly rainbow connected}…

Combinatorics · Mathematics 2017-07-18 Hui Lei , Shasha Li , Henry Liu , Yongtang Shi

An odd independent set $S$ in a graph $G=(V,E)$ is an independent set of vertices such that, for every vertex $v \in V \setminus S$, either $N(v) \cap S = \emptyset$ or $|N(v) \cap S| \equiv 1$ (mod 2), where $N(v)$ stands for the open…

Combinatorics · Mathematics 2026-02-17 Yair Caro , Mirko Petruševski , Riste Škrekovski , Zsolt Tuza

In this paper we study the following problem proposed by Barrus, Ferrara, Vandenbussche, and Wenger. Given a graph $H$ and an integer $t$, what is $\operatorname{sat}_{t}\left(n, \mathfrak{R}{(H)}\right)$, the minimum number of edges in a…

Combinatorics · Mathematics 2019-10-24 António Girão , David Lewis , Kamil Popielarz

A graph has a locating rainbow coloring if every pair of its vertices can be connected by a path passing through internal vertices with distinct colors and every vertex generates a unique rainbow code. The minimum number of colors needed…

Combinatorics · Mathematics 2024-10-15 Ariestha Widyastuty Bustan , A. N. M Salman , Pritta Etriana Putri

We enumerate the independent sets of several classes of regular and almost regular graphs and compute the corresponding generating functions. We also note the relations between these graphs and other combinatorial objects and, in some…

Combinatorics · Mathematics 2007-05-23 Alexander Burstein , Sergey Kitaev , Toufik Mansour

Rainbow connection number, rc(G), of a connected graph G is the minimum number of colors needed to color its edges so that every pair of vertices is connected by at least one path in which no two edges are colored the same (Note that the…

Combinatorics · Mathematics 2011-07-25 Manu Basavaraju , L. Sunil Chandran , Deepak Rajendraprasad , Arunselvan Ramaswamy

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…

Combinatorics · Mathematics 2023-04-25 Barnabás Janzer , Oliver Janzer

Fix a positive integer $n$ and consider the bipartite graph whose vertices are the $3$-element subsets and the $2$-element subsets of $[n]=\{1,2,\dots,n\}$, and there is an edge between $A$ and $B$ if $A\subset B$. We prove that the…

Combinatorics · Mathematics 2024-06-25 Thomas Kalinowski , Uwe Leck

An independent set in a graph G is a set of vertices no two of which are joined by an edge. A vertex-weighted graph associates a weight with every vertex in the graph. A vertex-weighted graph G is called a unique independence…

Computational Complexity · Computer Science 2009-07-02 Farzad Didehvar , Ali D. Mehrabi , Fatemeh Raee B

An $r$-regular graph is an $r$-graph, if every odd set of vertices is connected to its complement by at least $r$ edges. Let $G$ and $H$ be $r$-graphs. An $H$-coloring of $G$ is a mapping $f\colon E(G) \to E(H)$ such that each $r$ adjacent…

Combinatorics · Mathematics 2023-05-16 Yulai Ma , Davide Mattiolo , Eckhard Steffen , Isaak H. Wolf

An edge-colored graph $G$ is rainbow connected if any two vertices are connected by a path whose edges have distinct colors. The rainbow connection number of a connected graph $G$, denoted by $rc(G)$, is the smallest number of colors that…

Computational Complexity · Computer Science 2011-11-15 Xiaolong Huang , Xueliang Li , Yongtang Shi