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We develop terminology and methods for working with maximally oriented partially directed acyclic graphs (maximal PDAGs). Maximal PDAGs arise from imposing restrictions on a Markov equivalence class of directed acyclic graphs, or…

Statistics Theory · Mathematics 2018-06-20 Emilija Perković , Markus Kalisch , Maloes H. Maathuis

We call a graph $G$ an $(r,t)$-Ruzsa-Szemer\'edi graph if its edge set can be partitioned into $t$ edge-disjoint induced matchings, each of size $r$. These graphs were introduced in 1978 and has been extensively studied since then. In this…

Combinatorics · Mathematics 2015-12-25 Jacob Fox , Hao Huang , Benny Sudakov

Graph representation learning has rapidly emerged as a pivotal field of study. Despite its growing popularity, the majority of research has been confined to embedding single-layer graphs, which fall short in representing complex systems…

Machine Learning · Computer Science 2024-03-29 Marco Bongiovanni , Luca Gallo , Roberto Grasso , Alfredo Pulvirenti

The past decade has seen a flourishing of advances in harmonic analysis of graphs. They lie at the crossroads of graph theory and such analytical tools as graph Laplacians, Markov processes and associated boundaries, analysis of path-space,…

Dynamical Systems · Mathematics 2020-07-31 Sergey Bezuglyi , Palle E. T. Jorgensen

An interval graph is the intersection graph of a finite set of intervals on a line and a circular-arc graph is the intersection graph of a finite set of arcs on a circle. While a forbidden induced subgraph characterization of interval…

Discrete Mathematics · Computer Science 2014-02-12 Luciano N. Grippo , Martín D. Safe

In this paper we study the class of bi-arc digraphs, important from two seemingly unrelated perspectives. On the one hand, they are precisely the digraphs that admit certain polymorphisms of interest in the study of constraint satisfaction…

Data Structures and Algorithms · Computer Science 2020-03-03 Pavol Hell , Akbar Rafiey , Arash Rafiey

An $H$-graph is one representable as the intersection graph of connected subgraphs of a suitable subdivision of a fixed graph $H$, introduced by Bir\'{o}, Hujter and Tuza (1992). An $H$-graph is proper if the representing subgraphs of $H$…

Data Structures and Algorithms · Computer Science 2022-03-24 Deniz Ağaoğlu Çağırıcı , Petr Hliněný

Sparse-dense partitions was introduced by Feder, Hell, Klein, and Motwani [STOC 1999, SIDMA 2003] as a tool to solve partitioning problems. In this paper, the following result concerning independent sets in graphs having sparse-dense…

Discrete Mathematics · Computer Science 2022-08-10 Uéverton S. Souza

The neighborhood complex of a graph was introduced by Lov\'asz to provide topological lower bounds on chromatic number. More general homomorphism complexes of graphs were further studied by Babson and Kozlov. Such `Hom complexes' are also…

Combinatorics · Mathematics 2023-08-16 Anton Dochtermann , Anurag Singh

Proximity maps and regions are defined based on the relative allocation of points from two or more classes in an area of interest and are used to construct random graphs called proximity catch digraphs (PCDs) which have applications in…

Metric Geometry · Mathematics 2009-02-10 Elvan Ceyhan

Difference-in-Differences (DiD) is a widely used research design that often relies on a conditional parallel trends (CPT) assumption. In contrast to settings with unconfoundedness, where causal graphs provide powerful frameworks for…

Econometrics · Economics 2026-04-15 Michael C. Knaus , Henri Pfleiderer

A digraph consisting of a set of vertices $V$ and a set of arcs $E$ is called an interval digraph if there exists a family of closed intervals $\{I_u,J_u\}_{u \in V}$ such that $uv$ is an arc if and only if the intersection of $I_u$ and…

Combinatorics · Mathematics 2026-03-10 Ayelén Alcantar , Flavia Bonomo , Guillermo Durán , Nina Pardal

Let $G$ be a simple finite connected graph of order $n$ greater than or equal to $3$. We obtain the following results: (1). We apply a result of Hamada and Yoshimura from 1976 and some recent results of Alikhani and Soltani (2020) and…

Combinatorics · Mathematics 2026-04-09 Amitayu Banerjee , Alexa Gopaulsingh , Zalán Molnár

A matchstick graph is a crossing-free unit-distance graph in the plane. Harborth (1981) proposed the problem of determining whether there exists a matchstick graph in which every vertex has degree exactly $5$. In 1982, Blokhuis gave a proof…

Combinatorics · Mathematics 2022-11-02 Jérémy Lavollée , Konrad J. Swanepoel

We focus on strongly connected, strong for short, digraphs since in this setting distance is defined for every pair of vertices. Distance ideals generalize the spectrum and Smith normal form of several distance matrices associated with…

In graph-theoretical terms, an edge in a graph connects two vertices while a hyperedge of a hypergraph connects any more than one vertices. If the hypergraph's hyperedges further connect the same number of vertices, it is said to be…

Systems and Control · Electrical Eng. & Systems 2024-11-05 Shaoxuan Cui , Guofeng Zhang , Hildeberto Jardón-Kojakhmetov , Ming Cao

Let $G$ be a simple finite connected graph. The line graph $L(G)$ of graph $G$ is the graph whose vertices are the edges of $G$, where $ef \in E(L(G))$ when $e \cap f \neq \emptyset$. Iteratively, the higher order line graphs are defined…

Combinatorics · Mathematics 2024-10-08 Aryan Sanghi , Devsi Bantva , Sudebkumar Prasant Pal

With the explosive growth of information technology, multi-view graph data have become increasingly prevalent and valuable. Most existing multi-view clustering techniques either focus on the scenario of multiple graphs or multi-view…

Machine Learning · Computer Science 2021-10-25 Erlin Pan , Zhao Kang

In 1987 Hiroshi Maehara conjectured that a graph can be represented by vectors considered adjacent when not orthogonal (a faithful orthogonal representation) in codimension the minimum degree of the graph. Without settling the conjecture,…

Combinatorics · Mathematics 2026-01-06 H. Tracy Hall

A matchstick graph is a plane graph with edges drawn as unit distance line segments. This class of graphs was introduced by Harborth who conjectured that a matchstick graph on $n$ vertices can have at most $\lfloor 3n - \sqrt{12n -…

Combinatorics · Mathematics 2025-06-04 Panna Gehér , Géza Tóth