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Let $G$ be a graph with vertex set $V$. Two disjoint sets $V_1, V_2\subseteq V$ are called a total coalition in $G$, if neither $V_1$ and $V_2$ is a total dominating set of $G$ but $V_1\cup V_2$ is a total dominating set. A total coalition…

Combinatorics · Mathematics 2022-12-13 Saeid Alikhani , Davood Bakhshesh , Hamidreza Golmohammadi

A graph is closed when its vertices have a labeling by [n] with a certain property first discovered in the study of binomial edge ideals. In this article, we explore various aspects of closed graphs, including the number of closed labelings…

Combinatorics · Mathematics 2016-03-09 David A. Cox , Andrew Erskine

A graph in which all minimal zero forcing sets are in fact minimum size is called ``well-forced." This paper characterizes well-forced trees and presents an algorithm for determining which trees are well-forced. Additionally, we…

Combinatorics · Mathematics 2023-12-25 Cheryl Grood , Ruth Haas , Bonnie Jacob , Erika King , Shahla Nasserasr

We continue the study of balanceable graphs, defined by Caro, Hansberg, and Montejano in 2021 as graphs $G$ such that any $2$-coloring of the edges of a sufficiently large complete graph containing sufficiently many edges of each color…

Combinatorics · Mathematics 2024-09-17 Milad Ahanjideh , Martin Milanič , Mary Servatius

Clique-width is a well-studied graph parameter. For graphs of bounded clique-width, many problems that are NP-hard in general can be polynomial-time solvable. The fact motivates several studies to investigate whether the clique-width of…

Data Structures and Algorithms · Computer Science 2022-02-01 Yu Nakahata

Given a graph $G(V,E)$, a vertex subset $S$ of $G$ is called an open packing in $G$ if no pair of distinct vertices in $S$ have a common neighbour in $G$. The size of a largest open packing in $G$ is called the open packing number,…

Discrete Mathematics · Computer Science 2024-07-15 M. A. Shalu , V. K. Kirubakaran

A graph is an efficient open (resp.\ closed) domination graph if there exists a subset of vertices whose open (resp.\ closed) neighborhoods partition its vertex set. Graphs that are efficient open as well as efficient closed (shortly EOCD…

Combinatorics · Mathematics 2015-11-09 Sandi Klavzar , Iztok Peterin , Ismael G. Yero

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

A graph $G$ with four or more vertices is called bicritical if the removal of any pair of distinct vertices of $G$ results in a graph with a perfect matching. A bicritical graph is minimal if the deletion of each edge results in a…

Combinatorics · Mathematics 2024-10-15 Jing Guo , Hailun Wu , Heping Zhang

A graph is called t-perfect if its stable set polytope is defined by non-negativity, edge and odd-cycle inequalities. We show that it can be decided in polynomial time whether a given claw-free graph is t-perfect.

Discrete Mathematics · Computer Science 2013-10-31 Henning Bruhn , Oliver Schaudt

Let $G=(V,E)$ be a graph. If $G$ is a K\"onig graph or $G$ is a graph without 3-cycles and 5-cycle, we prove that the following conditions are equivalent: $\Delta_{G}$ is pure shellable, $R/I_{\Delta}$ is Cohen-Macaulay, $G$ is unmixed…

Combinatorics · Mathematics 2015-05-04 Iván Dario Castrillón , Roberto Cruz , Enrique Reyes

A \textit{maximum stable set} in a graph $G$ is a stable set of maximum cardinality. $S$ is a \textit{local maximum stable set} of $G$, and we write $S\in\Psi(G)$, if $S$ is a maximum stable set of the subgraph induced by $S\cup N(S)$,…

Discrete Mathematics · Computer Science 2010-08-18 Vadim E. Levit , Eugen Mandrescu

Let $G$ be a graph embedded in a surface and let $\mathcal F$ be a set of even faces of $G$ (faces bounded by a cycle of even length). The resonance graph of $G$ with respect to $\mathcal F$, denoted by $R(G;\mathcal F)$, is a graph such…

Combinatorics · Mathematics 2023-06-16 Niko Tratnik , Dong Ye

An independent set in a graph G is a set of vertices no two of which are joined by an edge. A vertex-weighted graph associates a weight with every vertex in the graph. A vertex-weighted graph G is called a unique independence…

Computational Complexity · Computer Science 2009-07-02 Farzad Didehvar , Ali D. Mehrabi , Fatemeh Raee B

For a given positive integer t we consider graphs having maximal independent sets of precisely t distinct cardinalities and restrict our attention to those that have no vertices of degree one. In the situation when t is four or larger and…

Combinatorics · Mathematics 2011-10-20 Bert L. Hartnell , Douglas F. Rall

A family of independent $r$-sets of a graph $G$ is an $r$-star if every set in the family contains some fixed vertex $v$. A graph is $r$-EKR if the maximum size of an intersecting family of independent $r$-sets is the size of an $r$-star.…

Combinatorics · Mathematics 2023-04-19 Jessica De Silva , Adam B. Dionne , Aidan Dunkelberg , Pamela E. Harris

\noindent A perfect dominating set in a graph $G=(V,E)$ is a subset $S \subseteq V$ such that each vertex in $V \setminus S$ has exactly one neighbor in $S$. A perfect coalition in $G$ consists of two disjoint sets of vertices $V_i$ and…

Combinatorics · Mathematics 2025-07-22 Doost Ali Mojdeh , Mohammad Reza Samadzadeh

We introduce and study the pinnacle sets of a simple graph $G$ with $n$ vertices. Given a bijective vertex labeling $\lambda\,:\,V(G)\rightarrow [n]$, the label $\lambda(v)$ of vertex $v$ is a pinnacle of $(G, \lambda)$ if…

Combinatorics · Mathematics 2024-07-01 Chassidy Bozeman , Christine Cheng , Pamela E. Harris , Stephen Lasinis , Shanise Walker

The notion of graph covers is a discretization of covering spaces introduced and deeply studied in topology. In discrete mathematics and theoretical computer science, they have attained a lot of attention from both the structural and…

Discrete Mathematics · Computer Science 2023-06-13 Jan Bok , Jiří Fiala , Nikola Jedličková , Jan Kratochvíl , Michaela Seifrtová

A graph $G=(V,E)$ is $\gamma$-excellent if $V$ is a union of all $\gamma$-sets of $G$, where $\gamma$ stands for the domination number. Let $\mathcal{I}$ be a set of all mutually nonisomorphic graphs and $\emptyset \not= \mathcal{H}…

Combinatorics · Mathematics 2020-10-08 Vladimir Samodivkin
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