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Grid intersection graphs are the intersection graphs of vertical and horizontal segments in the plane. When the bottom and respectively left endpoints of the vertical and horizontals segments belong to a line with negative slope, the graph…

Discrete Mathematics · Computer Science 2022-01-27 Irena Rusu

Each hereditary property can be characterized by its set of minimal obstructions; these sets are often unknown, or known but infinite. By allowing extra structure it is sometimes possible to describe such properties by a finite set of…

Combinatorics · Mathematics 2021-12-02 Santiago Guzmán-Pro , Pavol Hell , César Hernández-Cruz

We define the crossing graph of a given embedded graph (such as a road network) to be a graph with a vertex for each edge of the embedding, with two crossing graph vertices adjacent when the corresponding two edges of the embedding cross…

Data Structures and Algorithms · Computer Science 2017-09-20 David Eppstein , Siddharth Gupta

In descending generality I survey: five partial orderings of graphs, the induced-subgraph ordering, and examples like perfect, threshold, and mock threshold graphs. The emphasis is on how the induced subgraph ordering differs from other…

Combinatorics · Mathematics 2021-06-21 Thomas Zaslavsky

In the theory of line graphs of undirected graphs there exists an important theorem linking the incidence matrix of the root graph to the adjacency matrix of its line graph. For directed or mixed graphs, however, the exists no analogous…

Combinatorics · Mathematics 2022-05-12 Mohammad Abudayah , Omar Alomari , Torsten Sander

For a given hypergraph, an orientation can be assigned to the vertex-edge incidences. This orientation is used to define the adjacency and Laplacian matrices. In addition to studying these matrices, several related structures are…

Combinatorics · Mathematics 2015-09-08 Nathan Reff

A normal Helly circular-arc graph is the intersection graph of arcs on a circle of which no three or less arcs cover the whole circle. Lin, Soulignac, and Szwarcfiter [Discrete Appl. Math. 2013] characterized circular-arc graphs that are…

Discrete Mathematics · Computer Science 2014-05-05 Yixin Cao , Luciano N. Grippo , Martín D. Safe

In this article we introduce and study the intersection graph of graded ideals of graded rings. The intersection graph of $G-$graded ideals of a graded ring $(R,G)$ is a simple graph, denoted by $Gr_G(R)$, whose vertices are the nontrivial…

Rings and Algebras · Mathematics 2020-08-11 T. Alraqad , H. Saber , R. Abu-Dawwas

We study the complexity of the Graph Isomorphism problem on graph classes that are characterized by a finite number of forbidden induced subgraphs, focusing mostly on the case of two forbidden subgraphs. We show hardness results and develop…

Data Structures and Algorithms · Computer Science 2015-03-20 Stefan Kratsch , Pascal Schweitzer

Consider two horizontal lines in the plane. A pair of a point on the top line and an interval on the bottom line defines a triangle between two lines. The intersection graph of such triangles is called a simple-triangle graph. This paper…

Discrete Mathematics · Computer Science 2016-11-29 Asahi Takaoka

The undirected power graph (or simply power graph) of a group $G$, denoted by $P(G)$, is a graph whose vertices are the elements of the group $G$, in which two vertices $u$ and $v$ are connected by an edge between if and only if either…

Combinatorics · Mathematics 2023-05-09 Pallabi Manna , Peter J. Cameron , Ranjit Mehatari

The L-intersection graphs are the graphs that have a representation as intersection graphs of axis parallel shapes in the plane. A subfamily of these graphs are {L, |, --}-contact graphs which are the contact graphs of axis parallel L, |,…

Computational Geometry · Computer Science 2017-07-31 Daniel Gonçalves , Lucas Isenmann , Claire Pennarun

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

In an $\mathsf{L}$-embedding of a graph, each vertex is represented by an $\mathsf{L}$-segment, and two segments intersect each other if and only if the corresponding vertices are adjacent in the graph. If the corner of each…

Computational Geometry · Computer Science 2017-03-07 Abu Reyan Ahmed , Felice De Luca , Sabin Devkota , Alon Efrat , Md Iqbal Hossain , Stephen Kobourov , Jixian Li , Sammi Abida Salma , Eric Welch

A unit disk graph is the intersection graph of disks of equal radii in the plane. The class of unit disk graphs is hereditary, and therefore admits a characterization in terms of minimal forbidden induced subgraphs. In spite of quite active…

Combinatorics · Mathematics 2016-02-29 Aistis Atminas , Viktor Zamaraev

We introduce the class of circular-arc H-graphs, which generalizes circular-arc graphs, particularly circular-arc bigraphs. We investigate two types of ordering-based characterizations of circular-arc r-graphs. Finally, we provide forbidden…

Discrete Mathematics · Computer Science 2025-09-23 Indrajit Paul , Ashok Kumar Das

Intersection graphs are very important in both theoretical as well as application point of view. Depending on the geometrical representation, different type of intersection graphs are defined. Among them interval, circular-arc, permutation,…

Discrete Mathematics · Computer Science 2014-04-23 Madhumangal Pal

In a paired threshold graph, each vertex has a weight, and two vertices are adjacent if their weight sum is large enough and their weight difference is small enough. It generalizes threshold graphs and unit interval graphs, both very well…

Data Structures and Algorithms · Computer Science 2019-10-01 Guozhen Rong , Yixin Cao , Jianxin Wang

It has been known since 1991 that the problem of recognizing grid intersection graphs is NP-complete. Here we use a modified argument of the above result to show that even if we restrict to the class of unit grid intersection graphs…

Combinatorics · Mathematics 2013-06-11 Irina Mustaţă , Martin Pergel

We introduce a new subclass of chordal graphs that generalizes split graphs, which we call well-partitioned chordal graphs. Split graphs are graphs that admit a partition of the vertex set into cliques that can be arranged in a star…

Combinatorics · Mathematics 2020-02-26 Jungho Ahn , Lars Jaffke , O-joung Kwon , Paloma T. Lima