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Determining the crossing numbers of Cartesian products of small graphs with arbitrarily large paths has been an ongoing topic of research since the 1970s. Doing so requires the establishment of coincident upper and lower bounds; the former…

Combinatorics · Mathematics 2024-09-12 Zayed Asiri , Ryan Burdett , Markus Chimani , Michael Haythorpe , Alex Newcombe , Mirko H. Wagner

It is known that the number of directions formed by a Cartesian product $A \times B \subset AG(2,p)$ is at least $|A||B| - \min\{|A|,|B|\} + 2$, provided $p$ is prime and $|A||B|<p$. This implies the best known upper bound on the clique…

Combinatorics · Mathematics 2021-05-07 Chi Hoi Yip

An identifying code in a graph $G$ is a dominating set $C$ such that the closed neighborhood of each vertex in $G$ has a distinct intersection with $C$. In 2008, Gravier et al. determined the minimum cardinality of an identifying code of…

Combinatorics · Mathematics 2014-12-09 Yingnan Zhang , Min Feng , Kaishun Wang

The bandwidth of a graph is the labeling of vertices with minimum maximum edge difference. For many graph families this is NP-complete. A classic result computes the bandwidth for the hypercube. We generalize this result to give sharp lower…

Discrete Mathematics · Computer Science 2007-05-23 Tanya Y. Berger-Wolf , Mitchell A. Harris

In this paper, anti-van der Waerden numbers on Cartesian products of graphs are investigated and a conjecture made by Schulte, et al (see arXiv:1802.01509) is answered. In particular, the anti-van der Waerden number of the Cartesian product…

Combinatorics · Mathematics 2018-05-09 Hunter Rehm , Alex Schulte , Nathan Warnberg

Clique-width is a well-studied graph parameter owing to its use in understanding algorithmic tractability: if the clique-width of a graph class ${\cal G}$ is bounded by a constant, a wide range of problems that are NP-complete in general…

Combinatorics · Mathematics 2021-12-23 Konrad K. Dabrowski , Matthew Johnson , Daniël Paulusma

Gravier et al. investigated the identifying codes of Cartesian product of two graphs. In this paper we consider the identifying codes of lexicographic product G[H] of a connected graph G and an arbitrary graph H, and obtain the minimum…

Combinatorics · Mathematics 2013-12-20 Min Feng , Min Xu , Kaishun Wang

There has been significant research dedicated towards computing the crossing numbers of families of graphs resulting from the Cartesian products of small graphs with arbitrarily large paths, cycles and stars. For graphs with four or fewer…

Combinatorics · Mathematics 2021-06-08 Kieran Clancy , Michael Haythorpe , Alex Newcombe

A "clique minor" in a graph G can be thought of as a set of connected subgraphs in G that are pairwise disjoint and pairwise adjacent. The "Hadwiger number" h(G) is the maximum cardinality of a clique minor in G. This paper studies clique…

Combinatorics · Mathematics 2011-10-05 David R. Wood

The following theorem is proved: For all $k$-connected graphs $G$ and $H$ each with at least $n$ vertices, the treewidth of the cartesian product of $G$ and $H$ is at least $k(n -2k+2)-1$. For $n\gg k$ this lower bound is asymptotically…

Combinatorics · Mathematics 2013-10-02 David R. Wood

In this work, we study the $\delta$-chromatic number of a graph which is the chromatic number of the $\delta$-complement of a graph. We give a structure of the $\delta$-complements and sharp bounds on the $\delta$-chromatic numbers of the…

Combinatorics · Mathematics 2024-01-02 Wipawee Tangjai , Witsarut Pho-on , Panupong Vichitkunakorn

In this article we present the idea of clique ceiling numbers of the vertices of a given graph that has a universal vertex. We follow up with a polynomial-time algorithm to compute an upper bound for the clique number of such a graph using…

Combinatorics · Mathematics 2019-06-04 R. Dharmarajan , D. Ramachandran

Clique-width is a well-studied graph parameter. For graphs of bounded clique-width, many problems that are NP-hard in general can be polynomial-time solvable. The fact motivates several studies to investigate whether the clique-width of…

Data Structures and Algorithms · Computer Science 2022-02-01 Yu Nakahata

A bound on consecutive clique numbers of graphs is established. This bound is evaluated and shown to often be much better than the bound of the Kruskal-Katona theorem. A bound on non-consecutive clique numbers is also proven.

Combinatorics · Mathematics 2007-10-23 Andy Frohmader

The kernel of the natural projection of a graph product of groups onto their direct product is called the Cartesian subgroup of the graph product. This construction generalises commutator subgroups of right-angled Coxeter and Artin groups.…

Group Theory · Mathematics 2025-07-30 Fedor Vylegzhanin

In this paper we present a lower bound for the domination number of the Cartesian product of a path and a cycle, that is tight if the length of the cycle is a multiple of five. This bound improves the natural lower bound obtained by using…

Combinatorics · Mathematics 2024-09-25 José Juan Carreño , José Antonio Martínez , María Luz Puertas

The bandwidth of a graph G is the minimum of the maximum difference between adjacent labels when the vertices have distinct integer labels. We provide a polynomial algorithm to produce an optimal bandwidth labeling for graphs in a special…

Combinatorics · Mathematics 2007-05-23 Le Tu Quoc Hung , Maciej M. Syslo , Margaret L. Weaver , Douglas B. West

An identifying code in a graph is a dominating set that also has the property that the closed neighborhood of each vertex in the graph has a distinct intersection with the set. It was recently shown by Gravier, Moncel and Semri that the…

Combinatorics · Mathematics 2012-06-19 Douglas F. Rall , Kirsti Wash

The palette of a vertex v in a graph G is the set of colors assigned to the edges incident to v. The palette index of G is the minimum number of distinct palettes among the vertices, taken over all proper edge colorings of G. This paper…

Combinatorics · Mathematics 2025-01-14 Aleksander Vesel

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
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