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Twin-width is a graph width parameter recently introduced by Bonnet, Kim, Thomass\'{e} & Watrigant. Given two graphs $G$ and $H$ and a graph product $\star$, we address the question: is the twin-width of $G\star H$ bounded by a function of…

Combinatorics · Mathematics 2024-02-14 William Pettersson , John Sylvester

The packing number of a graph $G$ is the maximum number of closed neighborhoods of vertices in $G$ with pairwise empty intersections. Similarly, the open packing number of $G$ is the maximum number of open neighborhoods in $G$ with pairwise…

Combinatorics · Mathematics 2023-06-22 Doost Ali Mojdeh , Iztok Peterin , Babak Samadi , Ismael G. Yero

A graph is strongly perfect if every induced subgraph H has a stable set that meets every maximal clique of H. A graph is claw-free if no vertex has three pairwise non-adjacent neighbors. The characterization of claw-free graphs that are…

Combinatorics · Mathematics 2020-11-10 Maria Chudnovsky , Cemil Dibek

A set $S$ of vertices in a graph is an open packing if (open) neighborhoods of any two distinct vertices in $S$ are disjoint. In this paper, we consider the graphs that have a unique maximum open packing. We characterize the trees with this…

Combinatorics · Mathematics 2019-01-29 Boštjan Brešar , Kirsti Kuenzel , Douglas F. Rall

We give an affirmative answer to a long-standing conjecture of Thomassen, stating that every sufficiently highly connected graph has a $k$-vertex-connected orientation. We prove that a connectivity of order $O(k^2)$ suffices. As a key tool,…

Combinatorics · Mathematics 2025-03-12 Dániel Garamvölgyi , Tibor Jordán , Csaba Király , Soma Villányi

A graph is {\em perfect} if, in all its induced subgraphs, the size of a largest clique is equal to the chromatic number. Examples of perfect graphs include bipartite graphs, line graphs of bipartite graphs and the complements of such…

Combinatorics · Mathematics 2007-05-23 Gérard Cornuéjols

A graph is perfectly divisible if for each of its induced subgraph $H$, $V(H)$ can be partitioned into $A$ and $B$ such that $H[A]$ is perfect and $\omega(H[B]) < \omega(H)$, and a graph $G$ is perfectly weight divisible if for every…

Combinatorics · Mathematics 2026-03-06 Qiming Hu , Baogang Xu , Miaoxia Zhuang

We say that a graph $G$ on $n$ vertices is $\{H,F\}$-$o$-heavy if every induced subgraph of $G$ isomorphic to $H$ or $F$ contains two nonadjacent vertices with degree sum at least $n$. Generalizing earlier sufficient forbidden subgraph…

Combinatorics · Mathematics 2024-09-23 Wangyi Shang , Hajo Broersma , Shenggui Zhang , Binlong Li

Let $G$ be a graph and let Pm$(G)$ denote the number of perfect matchings of $G$. We denote the path with $m$ vertices by $P_m$ and the Cartesian product of graphs $G$ and $H$ by $G\times H$. In this paper, as the continuance of our paper…

Combinatorics · Mathematics 2007-05-23 Weigen Yan , Fuji Zhang

A connected graph $G$ with at least two vertices is matching covered if each of its edges lies in a perfect matching. A matching covered graph is minimal if the removal of any edge results in a graph that is no longer matching covered. An…

Combinatorics · Mathematics 2026-04-02 Xiaoling He , Fuliang Lu , Heping Zhang

Inspired by the definition of generalized wreath product of permutation groups, we define the generalized wreath product of graphs, containing the classical Cartesian and wreath product of graphs as particular cases. We prove that the…

Combinatorics · Mathematics 2016-02-16 Alfredo Donno

A pairing of a graph $G$ is a perfect matching of the complete graph having the same vertex set as $G$. If every pairing of $G$ can be extended to a Hamiltonian cycle of the underlying complete graph using only edges from $G$, then $G$ has…

Combinatorics · Mathematics 2022-03-22 John Baptist Gauci , Jean Paul Zerafa

The main focus of this thesis is a generalization of covering arrays, covering arrays on graphs. Two vectors v,w in Z_k^n are qualitatively independent if for all ordered pairs (a,b) in Z_k x Z_k there is a position i in the vectors where…

Combinatorics · Mathematics 2007-05-23 Karen Meagher

Let $G$ be an undirected graph of order $n$ and let $C_i$ be an $i$-cycle graph. $G$ is called pancyclic if $G$ contains a $C_i$ for any $i\in \{3,4,\ldots,n\}$. We show that the pancyclicity of specific Cayley graphs and the Cartesian…

Combinatorics · Mathematics 2023-09-06 Yusaku Nishimura

Given a graph $H$, a graph $G$ is $H$-free if $G$ does not contain $H$ as an induced subgraph. For a positive real number $t$, a non-complete graph $G$ is said to be $t$-tough if for every vertex cut $S$ of $G$, the ratio of $|S|$ to the…

Combinatorics · Mathematics 2023-03-21 Leyou Xu , Chengli Li , Bo Zhou

Graph products are characterized by the existence of non-trivial equivalence relations on the edge set of a graph that satisfy a so-called square property. We investigate here a generalization, termed RSP-relations. The class of graphs with…

Discrete Mathematics · Computer Science 2014-07-14 Marc Hellmuth , Tilen Marc , Lydia Ostermeier , Peter F. Stadler

Cartesian product networks are always regarded as a tool for ``combining'' two given networks with established properties to obtain a new one that inherits properties from both. For a graph $F=(V,E)$ and a set $S\subseteq V(F)$ of at least…

Combinatorics · Mathematics 2024-05-07 Rui Li , Gregory Gutin , He Zhang , Zhao Wang , Xiaoyan Zhang , Yaping Mao

A platypus graph is a non-hamiltonian graph for which every vertex-deleted subgraph is traceable. They are closely related to families of graphs satisfying interesting conditions regarding longest paths and longest cycles, for instance…

Combinatorics · Mathematics 2017-12-15 Jan Goedgebeur , Addie Neyt , Carol T. Zamfirescu

A $biased\ graph$ is a pair $(G,\mathcal{B})$, where $G$ is a graph and $\mathcal{B}$ is a collection of `balanced' circuits of $G$ such that no $\Theta$-subgraph of $G$ contains precisely two balanced circuits. We prove a Ramsey-type…

Combinatorics · Mathematics 2018-03-28 Peter Nelson , Sophia Park

For any hereditary graph class $F$, we construct optimal adjacency labeling schemes for the classes of subgraphs and induced subgraphs of Cartesian products of graphs in $F$. As a consequence, we show that, if $F$ admits efficient adjacency…

Data Structures and Algorithms · Computer Science 2024-09-13 Louis Esperet , Nathaniel Harms , Viktor Zamaraev
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