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Let $\gamma(G)$ denote the domination number of a graph $G$. A {\it Roman domination function} of a graph $G$ is a function $f: V\to\{0,1,2\}$ such that every vertex with 0 has a neighbor with 2. The {\it Roman domination number}…

Combinatorics · Mathematics 2009-09-22 Yunjian Wu

For a graph $G$, $\chi(G)$ will denote its chromatic number, and $\omega(G)$ its clique number. A graph $G$ is said to be perfectly divisible if for all induced subgraphs $H$ of $G$, $V(H)$ can be partitioned into two sets $A$, $B$ such…

Combinatorics · Mathematics 2021-04-08 T. Karthick , Jenny Kaufmann , Vaidy Sivaraman

For any graph $G$, the First-Fit (or Grundy) chromatic number of $G$, denoted by $\chi_{_{\sf FF}}(G)$, is defined as the maximum number of colors used by the First-Fit (greedy) coloring of the vertices of $G$. We call a family…

Combinatorics · Mathematics 2016-05-16 Manouchehr Zaker

A complete $k$-coloring of a graph $G=(V,E)$ is an assignment $\varphi:V\to\{1,\ldots,k\}$ of colors to the vertices such that no two vertices of the same color are adjacent, and the union of any two color classes contains at least one…

Discrete Mathematics · Computer Science 2013-12-31 Gabor Bacso , Piotr Borowiecki , Mihaly Hujter , Zsolt Tuza

Let G be a graph with a perfect matching. A complete forcing set of G is a subset of edges of G to which the restriction of every perfect matching is a forcing set of it. The complete forcing number of G is the minimum cardinality of…

Combinatorics · Mathematics 2021-02-09 Xin He , Heping Zhang

Zero forcing is a process that models the spread of information throughout a graph as white vertices are forced to turn blue using a color change rule. The idea of throttling, introduced in 2013 by Butler and Young, is to optimize the…

Combinatorics · Mathematics 2022-04-11 Jurgen Kritschgau , Josh Carlson

Zero forcing is an iterative process on a graph used to bound the maximum nullity. The process begins with select vertices as colored, and the remaining vertices can become colored under a specific color change rule. The goal is to find a…

Combinatorics · Mathematics 2017-09-27 Franklin H. J. Kenter , Jephian C. -H. Lin

This paper proves a conjecture generated by the artificial intelligence conjecturing program called \emph{TxGraffiti}. More specifically, we show that if $G$ is a connected, cubic, and claw-free graph, then $Z(G) \le \gamma(G) + 2$, where…

Combinatorics · Mathematics 2024-11-20 Randy R. Davila

Consider a finite and simple graph $G=(V,E)$ with maximum degree $\Delta$. A strong Roman dominating function over the graph $G$ is understood as a map $f : V (G)\rightarrow \{0, 1,\ldots , \left\lceil \frac{\Delta}{2}\right\rceil+ 1\}$…

Combinatorics · Mathematics 2019-12-04 S. Nazari-Moghaddam , M. Soroudi , S. M. Sheikholeslami , I. G. Yero

The cochromatic number $Z(G)$ of a graph $G$ is the fewest number of colors needed to color the vertices of $G$ so that each color class is a clique or an independent set. In a fractional cocoloring of $G$ a non-negative weight is assigned…

Combinatorics · Mathematics 2019-06-14 John Gimbel , André Kündgen , Michael Molloy

A vertex $v$ of a graph $G=(V,E)$ is said to be undefended with respect to a function $f: V \longrightarrow \{0,1,2\}$ if $f(v)=0$ and $f(u)=0$ for every vertex $u$ adjacent to $v$. We call the function $f$ a weak Roman dominating function…

Combinatorics · Mathematics 2018-03-20 Magdalena Valveny , Hebert Pérez-Rosés , Juan A. Rodríguez-Velázquez

The forcing number of a perfect matching $M$ in a graph $G$ is the smallest number of edges inside $M$ that can not be contained in other perfect matchings. The anti-forcing number of $M$ is the smallest number of edges outside $M$ whose…

Combinatorics · Mathematics 2020-12-25 Kai Deng , Huazhong Lü , Tingzeng Wu

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

A Roman dominating function (RD-function) on a graph $G = (V(G), E(G))$ is a labeling $f : V(G) \rightarrow \{0, 1, 2\}$ such that every vertex with label $0$ has a neighbor with label $2$. The weight $f(V(G))$ of a RD-function $f$ on $G$…

Combinatorics · Mathematics 2017-09-18 Vladimir Samodivkin

An automorphism group of a graph $G$ is the set of all permutations of the vertex set of $G$ that preserve adjacency and non adjacency of vertices in a graph. A fixing set of a graph $G$ is a subset of vertices of $G$ such that only the…

Combinatorics · Mathematics 2017-01-04 Hira Benish , Iqra Irshad , Min Feng , Imran Javaid

Motivated in part by an observation that the zero forcing number for the complement of a tree on $n$ vertices is either $n-3$ or $n-1$ in one exceptional case, we consider the zero forcing number for the complement of more general graphs…

Combinatorics · Mathematics 2023-03-13 Emelie Curl , Shaun Fallat , Ryan Moruzzi , Carolyn Reinhart , Derek Young

Given a finite graph $G$, the maximum length of a sequence $(v_1,\ldots,v_k)$ of vertices in $G$ such that each $v_i$ dominates a vertex that is not dominated by any vertex in $\{v_1,\ldots,v_{i-1}\}$ is called the Grundy domination number,…

Combinatorics · Mathematics 2020-10-05 Boštjan Brešar , Simon Brezovnik

The zero locus of a function f on a graph G is defined as the graph with vertex set consisting of all complete subgraphs of G, on which f changes sign and where x,y are connected if one is contained in the other. For d-graphs, finite simple…

Discrete Mathematics · Computer Science 2015-08-25 Oliver Knill

For any graph $G$ of order $p$, a bijection $f: V(G)\to [1,p]$ is called a numbering of the graph $G$ of order $p$. The strength $str_f(G)$ of a numbering $f: V(G)\to [1,p]$ of $G$ is defined by $str_f(G) = \max\{f(u)+f(v)\; |\; uv\in…

Combinatorics · Mathematics 2021-03-02 Zhen-Bin Gao , Gee-Choon Lau , Wai-Chee Shiu

Given a set $\mathcal{F}$ of graphs, a graph $G$ is $\mathcal{F}$-free if $G$ does not contain any member of $\mathcal{F}$ as an induced subgraph. Barrus, Kumbhat, and Hartke [M. D. Barrus, M. Kumbhat, and S. G. Hartke, Graph classes…

Combinatorics · Mathematics 2015-08-04 Michael D. Barrus , Stephen G. Hartke
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