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A connected 1-factorisation is a 1-factorisation of a hypergraph for which the union of each pair of distinct 1-factors is a connected hypergraph. A uniform 1-factorisation is a 1-factorisation of a hypergraph for which the union of each…

Combinatorics · Mathematics 2023-07-26 Barbara Maenhaut , Jeremy Mitchell , Anna Puskas

We introduce and study, for a process P delivering edges on the Cartesian product of the vertex sets of a given set of graphs, the P-product of these graphs, thereby generalizing many types of product graph. Analogous to the notion of a…

Combinatorics · Mathematics 2017-02-10 Izak Broere , Johannes Heidema

If each minimal dominating set in a graph is a minimum dominating set, then the graph is called well-dominated. Since the seminal paper on well-dominated graphs appeared in 1988, the structure of well-dominated graphs from several…

Combinatorics · Mathematics 2021-05-21 Douglas F. Rall

This paper is concerned with the recognition of approximate graph products with respect to the Cartesian product. Most graphs are prime, although they can have a rich product-like structure. The proposed algorithms are based on a local…

Discrete Mathematics · Computer Science 2014-07-14 Marc Hellmuth , Wilfried Imrich , Tomas Kupka

The 'boxicity' ('cubicity') of a graph G is the minimum natural number k such that G can be represented as an intersection graph of axis-parallel rectangular boxes (axis-parallel unit cubes) in $R^k$. In this article, we give estimates on…

Combinatorics · Mathematics 2013-05-23 L. Sunil Chandran , Wilfried Imrich , Rogers Mathew , Deepak Rajendraprasad

This paper is concerned with the linkedness of Cartesian products of complete graphs. A graph with at least $2k$ vertices is {\it $k$-linked} if, for every set of $2k$ distinct vertices organised in arbitrary $k$ pairs of vertices, there…

Combinatorics · Mathematics 2020-12-11 Leif K. Jorgensen , Guillermo Pineda-Villavicencio , Julien Ugon

Let $F$ be a strictly $1$-balanced $k$-graph on $s$ vertices with $t$ edges and $\delta_{F,d}^T$ be the infimum of $\delta>0$ such that for every $\alpha>0$ and sufficiently large $n\in \mathbb{N}$, every $k$-graph system $\mathbf…

Combinatorics · Mathematics 2025-07-18 Jie Han , Jie Hu , Shunan Wei , Donglei Yang

In this paper, we explore the concept of the ``matrix product of graphs," initially introduced by Prasad, Sudhakara, Sujatha, and M. Vinay. This operation involves the multiplication of adjacency matrices of two graphs with assigned labels,…

Combinatorics · Mathematics 2023-12-15 Farzad Maghsoudi , Babak Miraftab , Sho Suda

We provide a deterministic algorithm that finds, in $\epsilon^{-O(1)} n^2$ time, an $\epsilon$-regular Frieze-Kannan partition of a graph on $n$ vertices. The algorithm outputs an approximation of a given graph as a weighted sum of…

Combinatorics · Mathematics 2019-08-21 Jacob Fox , László Miklós Lovász , Yufei Zhao

Let $F$ be a graph on $r$ vertices and let $G$ be a graph on $n$ vertices. Then an $F$-factor in $G$ is a subgraph of $G$ composed of $n/r$ vertex-disjoint copies of $F$, if $r$ divides $n$. In other words, an $F$-factor yields a partition…

Combinatorics · Mathematics 2025-08-13 Fabian Burghart , Annika Heckel , Marc Kaufmann , Noela Müller , Matija Pasch

While graphs and abstract data structures can be large and complex, practical instances are often regular or highly structured. If the instance has sufficient structure, we might hope to compress the object into a more succinct…

Computational Complexity · Computer Science 2024-12-02 Shreya Gupta , Boyang Huang , Russell Impagliazzo , Stanley Woo , Christopher Ye

A graph $G$ factors into graphs $H$ and $K$ via a matrix product if $A = BC$, where $A$, $B$, and $C$ are the adjacency matrices of $G$, $H$, and $K$, respectively. The graph $G$ is prime if, in every such factorization, one of the factors…

Combinatorics · Mathematics 2026-01-01 Saieed Akbari , Mohamad Parsa Elahimanes , Bobby Miraftab

In this note, we extend results about unique $n^{\textrm{th}}$ roots and cancellation of finite disconnected graphs with respect to the Cartesian, the strong and the direct product, to the rooted hierarchical products, and to a modified…

Combinatorics · Mathematics 2026-01-13 Wilfried Imrich , Igor Klep , Daniel Smertnig

The hardcore model is a model of lattice gas systems which has received much attention in statistical physics, probability theory and theoretical computer science. It is the probability distribution over independent sets $I$ of a graph…

Computational Complexity · Computer Science 2010-06-01 Allan Sly

We study the exact learnability of real valued graph parameters $f$ which are known to be representable as partition functions which count the number of weighted homomorphisms into a graph $H$ with vertex weights $\alpha$ and edge weights…

Machine Learning · Computer Science 2016-06-14 Nadia Labai , Johann A. Makowsky

Let $D=(V,A)$ be a digraph of order $n$, $S$ a subset of $V$ of size $k$ and $2\le k\leq n$. A strong subgraph $H$ of $D$ is called an $S$-strong subgraph if $S\subseteq V(H)$. A pair of $S$-strong subgraphs $D_1$ and $D_2$ are said to be…

Combinatorics · Mathematics 2022-04-05 Yiling Dong , Gregory Gutin , Yuefang Sun

We investigate the computational complexity of the graph primality testing problem with respect to the direct product (also known as Kronecker, cardinal or tensor product). In [1] Imrich proves that both primality testing and a unique prime…

Computational Complexity · Computer Science 2025-11-06 Luca Calderoni , Luciano Margara , Moreno Marzolla

Given a class of graphs $\mathcal{H}$, the problem $\oplus\mathsf{Sub}(\mathcal{H})$ is defined as follows. The input is a graph $H\in \mathcal{H}$ together with an arbitrary graph $G$. The problem is to compute, modulo $2$, the number of…

Computational Complexity · Computer Science 2023-10-12 Leslie Ann Goldberg , Marc Roth

The practical application of graph prime factorization algorithms is limited in practice by unavoidable noise in the data. A first step towards error-tolerant "approximate" prime factorization, is the development of local approaches that…

Discrete Mathematics · Computer Science 2017-05-11 Marc Hellmuth , Wilfried Imrich , Werner Klöckl , Peter F. Stadler

This article investigates the isomorphism problem for graphs derived from the four standard graph products: Cartesian, Kronecker (direct), strong, and lexicographic product. We provide a complete characterization of all simple connected…

Combinatorics · Mathematics 2025-08-07 Priti Prasanna Mondal , M. Rajesh Kannan , Fouzul Atik