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We study the minimum rank of a (simple, undirected) graph, which is the minimum rank among all matrices in a space determined by the graph. We determine the exact set of graphs on eight vertices for which the nullity of a minimum rank…

Combinatorics · Mathematics 2025-06-13 Wayne Barrett , Mark Hunnell , John Hutchens , John Sinkovic

The power graph $\mathcal{P}(G)$ of a group $G$ is the simple graph with vertex set $G$ and two vertices are adjacent whenever one of them is a positive power of the other. In this paper, for a finite noncyclic nilpotent group $G$, we study…

Combinatorics · Mathematics 2021-08-16 Ramesh Prasad Panda , Kamal Lochan Patra , Binod Kumar Sahoo

In this paper, we study a dynamic coloring of the vertices of a graph $G$ that starts with an initial subset $S$ of colored vertices, with all remaining vertices being non-colored. At each discrete time interval, a colored vertex with…

Combinatorics · Mathematics 2016-10-27 Randy Davila , Michael Henning

In this paper we compare the brushing number of a graph with the zero-forcing number of its line graph. We prove that the zero-forcing number of the line graph is an upper bound for the brushing number by constructing a brush configuration…

Combinatorics · Mathematics 2020-08-25 Aras Erzurumluoglu , David Pike , Karen Meagher

The undirected power graph (or simply power graph) of a group $G$, denoted by $P(G)$, is a graph whose vertices are the elements of the group $G$, in which two vertices $u$ and $v$ are adjacent if and only if either $u=v^m$ or $v=u^n$ for…

Combinatorics · Mathematics 2023-09-04 Santanu Mandal , Pallabi Manna

Recently, there have been found new relations between the zero forcing number and the minimum rank of a graph with the algebraic co-rank. We continue on this direction by giving a characterization of the graphs with real algebraic co-rank…

Combinatorics · Mathematics 2020-05-06 Carlos A. Alfaro

Let G be a simple finite graph such that each vertex has an integer value and different vertices have different values. Let S be a finite non-empty set of primes. We call G an S-graph if any two vertices are connected by an edge if and only…

Combinatorics · Mathematics 2014-08-26 K. Győry , L. Hajdu , R. Tijdeman

A graph $G$ is $H$-free if any subset of $V(G)$ does not induce a subgraph of $G$ that is isomorphic to $H$. Given a graph $H$, we present sufficient and necessary conditions for a graph $G$ such that $G/e$ is $H$-free for any edge $e$ in…

Combinatorics · Mathematics 2022-12-20 Hany Ibrahim , Peter Tittmann

In a graph G, a dominating set Df subset of V (G) is called a dom-forcing set if the sub-graph induced by Df must form a zero forcing set. The minimum cardinality of such a set is known as the dom-forcing number of the graph G, denoted by…

Combinatorics · Mathematics 2025-05-19 Susanth P , Charles Dominic , Premodkumar K P

Zero forcing is an iterative graph coloring process studied for its wide array of applications. In this process, the vertices of the graph are initially designated as blue or white, and a zero forcing set is a set of initially blue vertices…

Combinatorics · Mathematics 2026-03-23 Asher Brown , Mark Hunnell , Za'Kiyah Toomer-Sanders , Sarah Weber

The \emph{power graph} $P(G)$ of a group $G$ is the graph whose vertex set is $G$, with $x$ and $y$ joined if one is a power of the other; the \emph{directed power graph} $\vec{P}(G)$ has the same vertex set, with an arc from $x$ to $y$ if…

Group Theory · Mathematics 2019-05-31 Peter J. Cameron , Horacio Guerra , Šimon Jurina

Let $G$ be a graph, and $Z$ a subset of its vertices, which we color black, while the remaining are colored white. We define the skew color change rule as follows: if $u$ is a vertex of $G$, and exactly one of its neighbors $v$, is white,…

Combinatorics · Mathematics 2014-05-16 Luz M. DeAlba

A near-factor of a finite simple graph $G$ is a matching that saturates all vertices except one. A graph $G$ is said to be near-factor-critical if the deletion of any vertex from $G$ results in a subgraph that has a near-factor. We prove…

Combinatorics · Mathematics 2014-05-19 Kuo-Ching Huang , Ko-Wei Lih

Let $\Gamma_G$ denote a graph associated with a group $G$. A compelling question about finite groups asks whether or not a finite group $H$ must be nilpotent provided $\Gamma_H$ is isomorphic to $\Gamma_G$ for a finite nilpotent group $G$.…

Group Theory · Mathematics 2023-09-22 Valentina Grazian , Andrea Lucchini , Carmine Monetta

A class $\mathcal G$ of graphs is $\chi$-bounded if there is a function $f$ such that for every graph $G\in \mathcal G$ and every induced subgraph $H$ of $G$, $\chi(H)\le f(\omega(H))$. In addition, we say that $\mathcal G$ is polynomially…

Combinatorics · Mathematics 2019-06-17 Ringi Kim , O-joung Kwon , Sang-il Oum , Vaidy Sivaraman

The prime graph $\Gamma(G)$ of a finite group $G$ (also known as the Gruenberg-Kegel graph) has as its vertices the prime divisors of $|G|$, and $p\text-q$ is an edge in $\Gamma(G)$ if and only if $G$ has an element of order $pq$. Since…

Group Theory · Mathematics 2022-11-30 Ziyu Huang , Thomas Michael Keller , Shane Kissinger , Wen Plotnick , Maya Roma , Yong Yang

Zero forcing is a binary coloring game on a graph where a set of filled vertices can force non-filled vertices to become filled following a color change rule. In 2008, the zero forcing number of a graph was shown to be an upper bound on its…

Combinatorics · Mathematics 2025-08-12 Thomas R. Cameron , Jonad Pulaj

Let $G$ be a finite group. The co-prime order graph of $G$ is the graph whose vertex set is $G$, and two distinct vertices $x,y$ are adjacent if gcd$(o(x),o(y))$ is either $1$ or a prime, where $o(x)$ and $o(y)$ are the orders of $x$ and…

Combinatorics · Mathematics 2021-09-28 Xuanlong Ma , Zhonghua Wang

In this paper, we study minimal (with respect to inclusion) zero forcing sets. We first investigate when a graph can have polynomially or exponentially many distinct minimal zero forcing sets. We also study the maximum size of a minimal…

Combinatorics · Mathematics 2022-04-18 Boris Brimkov , Joshua Carlson

A sequence $D=(d_1,d_2,\ldots,d_n)$ of non-negative integers is called a graphic sequence if there is a simple graph with vertices $v_1,v_2,\ldots,v_n$ such that the degree of $v_i$ is $d_i$ for $1\leq i\leq n$. Given a graph theoretical…

Combinatorics · Mathematics 2025-04-23 Peiyi Duan , Yingzhi Tian