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Given a graph $G$, denote by $\Delta$, $\bar{d}$ and $\chi^\prime$ the maximum degree, the average degree and the chromatic index of $G$, respectively. A simple graph $G$ is called {\it edge-$\Delta$-critical} if $\chi^\prime(G)=\Delta+1$…

Combinatorics · Mathematics 2017-08-07 Yan Cao , Guantao Chen , Suyun Jiang , Huiqing Liu , Fuliang Lu

The Wiener index of a strong digraph $D$ is defined as the sum of the distances between all ordered pairs of vertices. This definition has been extended to digraphs that are not necessarily strong by defining the distance from a vertex $a$…

Combinatorics · Mathematics 2022-09-20 Peter Dankelmann

A graph is $c$-closed when every pair of nonadjacent vertices has at most $c-1$ common neighbors. In $c$-Closed Vertex Deletion, the input is a graph $G$ and an integer $k$ and we ask whether $G$ can be transformed into a $c$-closed graph…

Data Structures and Algorithms · Computer Science 2025-11-18 Lisa Lehner , Christian Komusiewicz , Luca Pascal Staus

A $(0,1)$-labelling of a set is said to be {\em friendly} if approximately one half the elements of the set are labelled 0 and one half labelled 1. Let $g$ be a labelling of the edge set of a graph that is induced by a labelling $f$ of the…

Combinatorics · Mathematics 2024-04-16 Leroy Beasley , David Brown , Jonathan Mousley , Manuel Santana

Let $G=(V,E)$ be a simple graph. A set $S\subseteq V(G)$ is called an outer-connected dominating set (or ocd-set) of $G$, if $S$ is a dominating set of $G$ and either $S=V(G)$ or $V\backslash S$ is a connected graph. In this paper we…

Combinatorics · Mathematics 2024-02-19 Saeid Alikhani , Mohammad H. Akhbari , C. Eslahchi , Roslan Hasni

The conflict-free chromatic index of a graph $G$ is the minimum number of colours in an edge colouring of $G$ such that the neighbourhood of every edge contains a colour appearing exactly once. Its vertex analogue is the conflict-free…

Combinatorics · Mathematics 2026-04-27 Mateusz Kamyczura , Jakub Przybyło

Let $G=(V,E)$ be a connected graph, let $v\in V$ be a vertex and let $e=uw\in E$ be an edge. The distance between the vertex $v$ and the edge $e$ is given by $d_G(e,v)=\min\{d_G(u,v),d_G(w,v)\}$. A vertex $w\in V$ distinguishes two edges…

Combinatorics · Mathematics 2016-02-02 Aleksander Kelenc , Niko Tratnik , Ismael G. Yero

A graph $G=(V,E)$ is a pairwise compatibility graph (PCG) if there exists an edge-weighted tree $T$ and two non-negative real numbers $d_{min}$ and $d_{max}$, $d_{min} \leq d_{max}$, such that each node $u \in V$ is uniquely associated to a…

Discrete Mathematics · Computer Science 2017-07-25 Pierluigi Baiocchi , Tiziana Calamoneri , Angelo Monti , Rossella Petreschi

An undirected graph is said to be cordial if there is a friendly (0,1)-labeling of the vertices that induces a friendly (0,1)-labeling of the edges. An undirected graph $G$ is said to be $(2,3)$-orientable if there exists a friendly…

Combinatorics · Mathematics 2024-08-27 LeRoy b. Beasley

The edges surrounding a face of a map $M$ form a cycle $C$, called the boundary cycle of the face, and $C$ is often not a simple cycle. If the map $M$ is arc-transitive, then there is a cyclic subgroup of automorphisms of $M$ which leaves…

Combinatorics · Mathematics 2021-11-05 Jiyong Chen , Cai Heng Li , Cheryl E. Praeger , Shu-Jiao Song

A strict confluent (SC) graph drawing is a drawing of a graph with vertices as points in the plane, where vertex adjacencies are represented not by individual curves but rather by unique smooth paths through a planar system of junctions and…

Computational Geometry · Computer Science 2019-08-16 Henry Förster , Robert Ganian , Fabian Klute , Martin Nöllenburg

The distinguishing number $D(G)$ of a graph $G$ is the least integer $d$ such that $G$ has a vertex labeling with $d$ labels that is preserved only by a trivial automorphism. The distinguishing chromatic number $\chi_{D}(G)$ of $G$ is…

Combinatorics · Mathematics 2017-09-29 Saeid Alikhani , Samaneh Soltani

The vertex (resp. edge) metric dimension of a graph G is the size of a smallest vertex set in G which distinguishes all pairs of vertices (resp. edges) in G and it is denoted by dim(G) (resp. edim(G)). The upper bounds dim(G) <= 2c(G) - 1…

Combinatorics · Mathematics 2022-03-15 Martin Knor , Jelena Sedlar , Riste Škrekovski

We consider infinite graphs. The distinguishing number $D(G)$ of a graph $G$ is the minimum number of colours in a vertex colouring of $G$ that is preserved only by the trivial automorphism. An analogous invariant for edge colourings is…

Combinatorics · Mathematics 2021-05-18 Wilfried Imrich , Rafał Kalinowski , Monika Pilśniak , Mohammad H. Shekarriz

For any graph~\(G,\) a set of vertices~\({\cal V}\) is said to be dominating if every vertex of~\(G\) contains at least one node of~\(G\) and separating if each vertex~\(v\) contains a unique neighbour~\(u_v \in {\cal V}\) that is adjacent…

Combinatorics · Mathematics 2021-08-17 Ghurumuruhan Ganesan

This article investigates the isomorphism problem for graphs derived from the four standard graph products: Cartesian, Kronecker (direct), strong, and lexicographic product. We provide a complete characterization of all simple connected…

Combinatorics · Mathematics 2025-08-07 Priti Prasanna Mondal , M. Rajesh Kannan , Fouzul Atik

For a class $\mathcal C$ of graphs, we define $\mathcal C$-edge-brittleness of a graph $G$ as the minimum $\ell$ such that the vertex set of $G$ can be partitioned into sets inducing a subgraph in $\mathcal C$ and there are $\ell$ edges…

Combinatorics · Mathematics 2020-11-05 Ringi Kim , Sergey Norin , Sang-il Oum

Say that an edge of a graph G dominates itself and every other edge adjacent to it. An edge dominating set of a graph G = (V,E) is a subset of edges E' of E which dominates all edges of G. In particular, if every edge of G is dominated by…

Discrete Mathematics · Computer Science 2013-03-12 Min Chih Lin , Michel J. Mizrahi , Jayme L. Szwarcfiter

An identifying code of a (di)graph $G$ is a dominating subset $C$ of the vertices of $G$ such that all distinct vertices of $G$ have distinct (in)neighbourhoods within $C$. In this paper, we classify all finite digraphs which only admit…

Discrete Mathematics · Computer Science 2013-10-11 Florent Foucaud , Reza Naserasr , Aline Parreau

Dominating sets and resolving sets have important applications in control theory and computer science. In this paper, we introduce an edge-analog of the classical dominant metric dimension of graphs. By combining the concepts of a…

Combinatorics · Mathematics 2022-11-18 H. M. Ikhlaq , S. Hayat , H. M. A. Siddiqui