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A graph is circle if there is a family of chords in a circle such that two vertices are adjacent if the corresponding chords cross each other. There are diverse characterizations of circle graphs, many of them using the notions of local…

Discrete Mathematics · Computer Science 2020-06-02 Nina Pardal

Interval graphs are intersection graphs of closed intervals of the real-line. The well-known computational problem, called recognition, asks whether an input graph $G$ can be represented by closed intervals, i.e., whether $G$ is an interval…

Discrete Mathematics · Computer Science 2014-05-20 Pavel Klavík , Jan Kratochvíl , Yota Otachi , Toshiki Saitoh , Tomáš Vyskočil

A proper edge-coloring of a graph is an interval coloring if the labels on the edges incident to any vertex form an interval of consecutive integers. Interval thickness s(G) of a graph G is the smallest number of interval colorable graphs…

Combinatorics · Mathematics 2022-05-13 Maria Axenovich , Michael Zheng

Characterisations of interval graphs, comparability graphs, co-comparability graphs, permutation graphs, and split graphs in terms of linear orderings of the vertex set are presented. As an application, it is proved that interval graphs,…

Discrete Mathematics · Computer Science 2011-10-05 David R. Wood

The \emph{thinness} of a graph is a width parameter that generalizes some properties of interval graphs, which are exactly the graphs of thinness one. Graphs with thinness at most two include, for example, bipartite convex graphs. Many…

Discrete Mathematics · Computer Science 2023-10-06 Flavia Bonomo-Braberman , Gastón Abel Brito

We work out the graph limit theory for dense interval graphs. The theory developed departs from the usual description of a graph limit as a symmetric function $W(x,y)$ on the unit square, with $x$ and $y$ uniform on the interval $(0,1)$.…

Combinatorics · Mathematics 2011-02-15 Persi Diaconis , Susan Holmes , Svante Janson

The sets of vertices and edges of an undirected, simple, finite, connected graph $G$ are denoted by $V(G)$ and $E(G)$, respectively. An arbitrary nonempty finite subset of consecutive integers is called an interval. An injective mapping…

Discrete Mathematics · Computer Science 2014-10-30 Narine N. Davtyan , Arpine M. Khachatryan , Rafayel R. Kamalian

In this paper, we study different forbidden subgraph characterizations of the prime-order element graph $\Gamma(G)$ defined on a finite group $G$. Its set of vertices is the group $G$ and two vertices $x,y \in G$ are adjacent if the order…

Combinatorics · Mathematics 2024-12-31 Tapa Manna , Angsuman Das , Baby Bhattacharya

We provide upper bounds on the $L(p,q)$-labeling number of graphs which have interval (or circular-arc) representations via simple greedy algorithms. We prove that there exists an $L(p,q)$-labeling with span at most…

Combinatorics · Mathematics 2023-07-28 Mehmet Akif Yetim

Threshold tolerance graphs and their complement graphs, known as co-TT graphs, were introduced by Monma, Reed, and Trotter[24]. Building on this, Hell et al.[19] introduced the concept of negative interval. Then they proceeded to define…

Discrete Mathematics · Computer Science 2024-11-15 Ashok Kumar Das , Indrajit Paul

We consider the problems of finding optimal identifying codes, (open) locating-dominating sets and resolving sets of an interval or a permutation graph. In these problems, one asks to find a subset of vertices, normally called a…

Discrete Mathematics · Computer Science 2017-07-17 Florent Foucaud , George B. Mertzios , Reza Naserasr , Aline Parreau , Petru Valicov

We introduce a variation of interval graphs, called veto interval (VI) graphs. A VI graph is represented by a set of closed intervals, each containing a point called a veto mark. The edge $ab$ is in the graph if the intervals corresponding…

Erd\H{o}s, Fajtlowicz and Staton asked for the least integer $f(k)$ such that every graph with more than $f(k)$ vertices has an induced regular subgraph with at least $k$ vertices. Here we consider the following relaxed notions. Let $g(k)$…

Combinatorics · Mathematics 2018-11-20 Yair Caro , Raphael Yuster

A graph $G = (\{1, 2, \ldots, n\}, E)$ is $12$-representable if there is a word $w$ over $\{1, 2, \ldots, n\}$ such that two vertices $i$ and $j$ with $i < j$ are adjacent if and only if every $j$ occurs before every $i$ in $w$. These…

Combinatorics · Mathematics 2023-08-31 Asahi Takaoka

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

Min orderings give a vertex ordering characterization, common to some graphs and digraphs such as interval graphs, complements of threshold tolerance graphs (known as co-TT graphs), and two-directional orthogonal ray graphs. An adjusted…

Discrete Mathematics · Computer Science 2018-10-16 Asahi Takaoka

We introduce the concept of link-irregular labelings for graphs, extending the notion of link-irregular graphs through edge labeling with positive integers. A labeling is link-irregular if every vertex has a uniquely labeled subgraph…

Combinatorics · Mathematics 2025-07-01 Alexander Bastien , Omid Khormali

A \emph{mixed interval graph} is an interval graph that has, for every pair of intersecting intervals, either an arc (directed arbitrarily) or an (undirected) edge. We are particularly interested in scenarios where edges and arcs are…

Discrete Mathematics · Computer Science 2024-08-09 Grzegorz Gutowski , Konstanty Junosza-Szaniawski , Felix Klesen , Paweł Rzążewski , Alexander Wolff , Johannes Zink

A self-contained graph is an infinite graph which is isomorphic to one of its proper induced subgraphs. In this paper, these graphs are studied by presenting some examples and defining some of their sub-structures such as removable…

Combinatorics · Mathematics 2016-11-04 Mohammad Hadi Shekarriz , Madjid Mirzavaziri

The series-parallel (SP) graphs are those containing no topological $K_{_4}$ and are considered trivial. We relax the prohibition distinguishing the SP graphs by forbidding only embeddings of $K_{_4}$ whose edges with both ends 3-valent…

Combinatorics · Mathematics 2010-12-30 Elad Aigner-Horev