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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

A graph $H$ is an induced subgraph of a graph $G$ if a graph isomorphic to $H$ can be obtained from $G$ by deleting vertices. Recently, there has been significant interest in understanding the unavoidable induced subgraphs for graphs of…

Combinatorics · Mathematics 2022-07-01 Robert Hickingbotham

We calculate the intersection ring of three-dimensional graph manifolds with rational coefficients and give an algebraic characterization of these rings when the manifold's underlying graph is a tree. We are able to use this…

Geometric Topology · Mathematics 2015-03-23 Margaret I. Doig , Peter D. Horn

It is well known that directed treewidth does not enjoy the nice algorithmic properties of its undirected counterpart. There exist, however, some positive results that, essentially, present XP algorithms for the problem of finding, in a…

Data Structures and Algorithms · Computer Science 2025-08-20 Raul Lopes , Ignasi Sau

The class of intersection bigraphs of unit intervals of the real line whose ends may be open or closed is called a class of mixed unit interval bigraphs. This class of bigraphs is a strict superclass of the class of unit interval bigraphs.…

Discrete Mathematics · Computer Science 2026-05-27 Ashok Kumar Das , Rajkamal Sahu , Amina Khatun

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

The pathwidth of a graph $G$ is the smallest $w\in \mathbb{N}$ such that $G$ can be constructed from a sequence of graphs, each on at most $w+1$ vertices, by gluing them together in a linear fashion. We provide a full classification of the…

Combinatorics · Mathematics 2024-12-30 Maria Chudnovsky , Sepehr Hajebi , Sophie Spirkl

A path graph is the intersection graph of paths in a tree. A directed path graph is the intersection graph of paths in a directed tree. Even if path graphs and directed path graphs are characterized very similarly, their recognition…

Data Structures and Algorithms · Computer Science 2025-05-07 Lorenzo Balzotti

For a set of non-negative integers $L$, the $L$-intersection number of a graph is the smallest number $l$ for which there is an assignment on the vertices to subsets $A_v \subseteq \{1,\dots, l\}$, such that every two vertices $u,v$ are…

Combinatorics · Mathematics 2013-08-22 Zeinab Maleki , Behnaz Omoomi

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

A vertex whose removal in a graph $G$ increases the number of components of $G$ is called a cut vertex. For all $n,c$, we determine the maximum number of connected induced subgraphs in a connected graph with order $n$ and $c$ cut vertices,…

Combinatorics · Mathematics 2019-10-11 Audace A. V. Dossou-Olory

The subgraph number of a vertex in a graph is defined as the number of connected subgraphs containing that vertex. The graph and its vertex which correspond to the minimum subgraph number among all graphs on $n$ vertices and $k$ cut…

Combinatorics · Mathematics 2025-08-11 Dinesh Pandey , Peruvemba Sundaram Ravi

It was noted already in the 90s that many classic graph classes, such as interval, chordal, and bipartite graphs, can be characterized by the existence of an ordering of the vertices avoiding some ordered subgraphs, called patterns. Very…

Discrete Mathematics · Computer Science 2021-12-07 Laurent Feuilloley , Michel Habib

Graph isomorphism, subgraph isomorphism, and maximum common subgraphs are classical well-investigated objects. Their (parameterized) complexity and efficiently tractable cases have been studied. In the present paper, for a given set of…

Data Structures and Algorithms · Computer Science 2024-03-22 Dieter Rautenbach , Florian Werner

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

Chordal graphs are the graphs in which every cycle of length at least four has a chord. A set $S$ is a vertex separator for vertices $a$ and $b$ if the removal of $S$ of the graph separates $a$ and $b$ into distinct connected components. A…

Discrete Mathematics · Computer Science 2018-03-22 Sérgio H. Nogueira , Vinicius F. dos Santos

The Johnson graph J(n,N) is defined as the graph whose vertices are the n-subsets of the set {1,2,...,N}, where two vertices are adjacent if they share exactly n - 1 elements. Unlike Johnson graphs, induced subgraphs of Johnson graphs (JIS…

Combinatorics · Mathematics 2012-05-23 Ramin Naimi , Jeffrey Shaw

Let $\mathbb{G}_{n,\gamma}$ be the set of simple and connected graphs on $n$ vertices and with domination number $\gamma$. The graph with minimum spectral radius among $\mathbb{G}_{n,\gamma}$ is called the minimizer graph. In this paper, we…

Combinatorics · Mathematics 2022-12-05 Chang Liu , Jianping Li

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

Subgraph detection has recently been one of the most studied problems in the CONGEST model of distributed computing. In this work, we study the distributed complexity of problems closely related to subgraph detection, mainly focusing on…

Distributed, Parallel, and Cluster Computing · Computer Science 2021-12-08 Janne H. Korhonen , Amir Nikabadi