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Let $G$ be a graph. The maximum nullity of $G$, denoted by $M(G)$, is defined to be the largest possible nullity over all real symmetric matrices $A$ whose $a_{ij}\neq 0$ for $i\neq j$, whenever two vertices $u_i$ and $u_j$ of $G$ are…

Combinatorics · Mathematics 2017-05-30 Saieed Akbari , Ebrahim Vatandoost , Yasser Golkhandy Pour

For a positive integer $k$, a $k$-colouring of a graph $G=(V,E)$ is a mapping $c: V\rightarrow\{1,2,...,k\}$ such that $c(u)\neq c(v)$ whenever $uv\in E$. The Colouring problem is to decide, for a given $G$ and $k$, whether a $k$-colouring…

Computational Complexity · Computer Science 2016-02-16 Petr A. Golovach , Matthew Johnson , Daniël Paulusma , Jian Song

In this paper, we initiate the study of the inverse eigenvalue problem for probe graphs. A probe graph is a graph whose vertices are partitioned into probe vertices and non-probe vertices such that the non-probe vertices form an independent…

Combinatorics · Mathematics 2024-03-01 Emelie Curl , Jürgen Kritschgau , Carolyn Reinhart , Hein van der Holst

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

Let ${\rm Z}(G)$ and ${\rm gp}(G)$ be the zero forcing number and the general position number of a graph $G$, respectively. Known results imply that ${\rm gp}(T)\ge {\rm Z}(T) + 1$ holds for every nontrivial tree $T$. It is proved that the…

Combinatorics · Mathematics 2021-12-21 Hongbo Hua , Xinying Hua , Sandi Klavžar

The zero forcing number was introduced as a combinatorial bound on the maximum nullity taken over the set of real symmetric matrices that respect the pattern of an underlying graph. The $Z_q$-forcing game is an analog to the standard zero…

Combinatorics · Mathematics 2023-05-22 Jorge Blanco , Stephanie Einstein , Caleb Hostetler , Jurgen Kritschgau , Daniel Ogbe

Zero forcing is a process on graphs in which a color change rule is used to force vertices to become blue. The amount of time taken for all vertices in the graph to become blue is the propagation time. Throttling minimizes the sum of the…

Combinatorics · Mathematics 2024-05-07 Emily Cairncross , Joshua Carlson , Peter Hollander , Benjamin Kitchen , Emily Lopez , Ashley Zhuang

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

For graph classes $P_1,...,P_k$, Generalized Graph Coloring is the problem of deciding whether the vertex set of a given graph $G$ can be partitioned into subsets $V_1,...,V_k$ so that $V_j$ induces a graph in the class $P_j$…

Combinatorics · Mathematics 2007-05-23 Vladimir E. Alekseev , Alastair Farrugia , Vadim V. Lozin

We study two weighted graph coloring problems, in which one assigns $q$ colors to the vertices of a graph such that adjacent vertices have different colors, with a vertex weighting $w$ that either disfavors or favors a given color. We…

Mathematical Physics · Physics 2015-05-13 Shu-Chiuan Chang , Robert Shrock

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

A total dominator coloring of a graph G is a proper coloring of G in which each vertex of the graph is adjacent to every vertex of some color class. The total dominator chromatic number of a graph is the minimum number of color classes in a…

Combinatorics · Mathematics 2021-04-27 Farshad Kazemnejad , Behnaz Pahlavsay , Elisa Palezzato , Michele Torielli

For an $n$-vertex graph $G$, let $z(G;k)$ denote the number of zero forcing sets of size $k$. A conjecture of Boyer et al. asserts that the path $P_n$ maximizes these numbers coefficientwise among all $n$-vertex graphs; equivalently, the…

Discrete Mathematics · Computer Science 2026-05-12 Samuel German

Let $G=(V,E)$ be a simple connected graph. A perfect matching (or Kekul\'e structure in chemical literature) of $G$ is a set of disjoint edges which covers all vertices of $G$. The anti-forcing number of $G$ is the smallest number of edges…

Combinatorics · Mathematics 2018-07-24 Neda Soltani , Saeid Alikhani

Let $G$ be a simple graph. The dominated coloring of $G$ is a proper coloring of $G$ such that each color class is dominated by at least one vertex. The minimum number of colors needed for a dominated coloring of $G$ is called the dominated…

Combinatorics · Mathematics 2019-10-10 Saeid Alikhani , Mohammad R. Piri

Chung, Graham and Wilson defined a set of graphs $\mathcal{H}$ to be forcing, if any sequence of graphs $\{G_n\}_{n \geq 0}$ with $|G_n| = n$ must be quasirandom, whenever $hom(H, G_n)= (p^{|E(H)|}+o(1))n^{|V(H)|}$ for every $H \in…

Combinatorics · Mathematics 2023-12-12 Nikola Spasić

A $k$-coloring of a graph is an assignment of integers between $1$ and $k$ to vertices in the graph such that the endpoints of each edge receive different numbers. We study a local variation of the coloring problem, which imposes further…

Combinatorics · Mathematics 2018-09-24 Jie You , Yixin Cao , Jianxin Wang

A coloring of a graph is an assignment of colors to its vertices such that adjacent vertices have different colors. Two colorings are equivalent if they induce the same partition of the vertex set into color classes. Let $\mathcal{A}(G)$ be…

Combinatorics · Mathematics 2024-03-11 Alain Hertz , Hadrien Mélot , Sébastien Bonte , Gauvain Devillez , Pierre Hauweele

The forcing number of a perfect matching of a graph was introduced by Harary et al., which originated from Klein and Randi\'{c}'s ideal of innate degree of freedom of Kekul\'{e} structure in molecular graph. On the opposite side in some…

Combinatorics · Mathematics 2020-04-13 Kai Deng , Saihua Liu , Xiangqian Zhou

The foldings of a connected graph $G$ are defined as follows. First, $G$ is a folding of itself. Let $G'$ be a graph obtained from $G$ by identifying two vertices at distance 2 in $G$. Then every folding of $G'$ is a folding of $G$. The…

Combinatorics · Mathematics 2008-02-25 David R. Wood