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Given a directed graph D = (V,A) we define its intersection graph I(D) = (A,E) to be the graph having A as a node-set and two nodes of I(D) are adjacent if their corresponding arcs share a common node that is the tail of at least one of…

Combinatorics · Mathematics 2013-06-19 Mourad Baïou , Laurent Beaudou , Zhentao Li , Vincent Limouzy

We consider several classes of intersection graphs of line segments in the plane and prove new equality and separation results between those classes. In particular, we show that: (1) intersection graphs of grounded segments and intersection…

Discrete Mathematics · Computer Science 2016-12-13 Jean Cardinal , Stefan Felsner , Tillmann Miltzow , Casey Tompkins , Birgit Vogtenhuber

In the Segment Intersection Graph Representation Problem, we want to represent the vertices of a graph as straight line segments in the plane such that two segments cross if and only if there is an edge between the corresponding vertices.…

Computational Geometry · Computer Science 2025-02-25 Simon D. Fink , Matthias Pfretzschner , Peter Stumpf

The most elusive problem around the class of circular-arc graphs is identifying all minimal graphs that are not in this class. The main obstacle is the lack of a systematic way of enumerating these minimal graphs. McConnell [FOCS 2001]…

Combinatorics · Mathematics 2025-03-18 Yixin Cao , Jan Derbisz , Tomasz Krawczyk

Let $\mathcal{A}$ be a set of positive numbers. A graph $G$ is called an $\mathcal{A}$-embeddable graph in $\mathbb{R}^d$ if the vertices of $G$ can be positioned in $\mathbb{R}^d$ so that the distance between endpoints of any edge is an…

Computational Complexity · Computer Science 2017-10-17 Mikhail Tikhomirov

A string graph is an intersection graph of curves in the plane. A $k$-string graph is a graph with a string representation in which every pair of curves intersects in at most $k$ points. We introduce the class of $(=k)$-string graphs as a…

Combinatorics · Mathematics 2023-08-31 Petr Chmel , Vít Jelínek

In this paper, we study arrangements of orthogonal circles, that is, arrangements of circles where every pair of circles must either be disjoint or intersect at a right angle. Using geometric arguments, we show that such arrangements have…

Computational Geometry · Computer Science 2019-08-27 Steven Chaplick , Henry Förster , Myroslav Kryven , Alexander Wolff

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

Unigraphs are graphs uniquely determined by their own degree sequence up to isomorphism. There are many subclasses of unigraphs such as threshold graphs, split matrogenic graphs, matroidal graphs, and matrogenic graphs. Unigraphs and these…

Data Structures and Algorithms · Computer Science 2019-04-23 Takashi Horiyama , Jun Kawahara , Shin-ichi Minato , Yu Nakahata

Grid graphs, and, more generally, $k\times r$ grid graphs, form one of the most basic classes of geometric graphs. Over the past few decades, a large body of works studied the (in)tractability of various computational problems on grid…

Data Structures and Algorithms · Computer Science 2021-07-01 Siddharth Gupta , Guy Sa'ar , Meirav Zehavi

Graph neural networks are promising architecture for learning and inference with graph-structured data. Yet difficulties in modelling the ``parts'' and their ``interactions'' still persist in terms of graph classification, where graph-level…

Machine Learning · Computer Science 2020-06-30 Kai Zhang , Yaokang Zhu , Jun Wang , Jie Zhang , Hongyuan Zha

An $H$-graph is an intersection graph of connected subgraphs of a suitable subdivision of a fixed graph $H$. Many important classes of graphs, including interval graphs, circular-arc graphs, and chordal graphs, can be expressed as…

Data Structures and Algorithms · Computer Science 2022-06-28 Deniz Ağaoğlu Çağırıcı , Peter Zeman

Unigraphs are graphs identifiable up to isomorphism from their degree sequences. Given a class $\mathcal{A}$ of graphs, we define the class of $\mathcal{A}$-unigraphs to be graphs identifiable from degree sequence and membership in…

Combinatorics · Mathematics 2024-06-07 R. Whitman

Golumbic, Lipshteyn, and Stern defined in 2009 the class of EPG graphs, the intersection graph class of edge paths on a grid. An EPG graph $G$ is a graph that admits a representation where its vertices correspond to paths in a grid $Q$,…

We consider the graph class Grounded-L corresponding to graphs that admit an intersection representation by L-shaped curves, where additionally the topmost points of each curve are assumed to belong to a common horizontal line. We prove…

Combinatorics · Mathematics 2019-11-06 Vít Jelínek , Martin Töpfer

We introduce the class of interval $H$-graphs, which is the generalization of interval graphs, particularly interval bigraphs. For a fixed graph $H$ with vertices $a_1,a_2,\dots,a_k$, we say that an input graph $G$ with given partition…

Discrete Mathematics · Computer Science 2025-03-04 Haiko Müller , Arash Rafiey

We collect some general results on graph limits associated to hereditary classes of graphs. As examples, we consider some classes defined by forbidden subgraphs and some classes of intersection graphs, including triangle-free graphs,…

Combinatorics · Mathematics 2013-03-29 Svante Janson

We investigate graphs that can be represented as vertex intersections of horizontal and vertical paths in a grid, the so called $B_0$-VPG graphs. Recognizing this class is an NP-complete problem. Although, there exists a polynomial time…

Combinatorics · Mathematics 2015-11-02 L. Alcón , F. Bonomo , M. P. Mazzoleni

A string graph is the intersection graph of curves in the plane. Kratochv\'il previously showed the existence of infinitely many obstacles: graphs that are not string graphs but for which any edge contraction or vertex deletion produces a…

Combinatorics · Mathematics 2025-09-03 Maria Chudnovsky , David Eppstein , David Fischer

We introduce a new class of intersection graphs, the edge intersection graphs of paths on a triangular grid, called EPGt graphs. We show similarities and differences from this new class to the well-known class of EPG graphs. A turn of a…

Discrete Mathematics · Computer Science 2022-03-09 Vitor T. F. de Luca , María Pía Mazzoleni , Fabiano S. Oliveira , Tanilson D. Santos , Jayme L. Szwarcfiter