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For a degree sequence, we define the set of edges that appear in every labeled realization of that sequence as forced, while the edges that appear in none as forbidden. We examine structure of graphs whose degree sequences contain either…

Combinatorics · Mathematics 2019-11-28 Brian Cloteaux

The \emph{zero forcing number}, $Z(G)$, of a graph $G$ is the minimum cardinality of a set $S$ of black vertices (whereas vertices in $V(G) \setminus S$ are colored white) such that $V(G)$ is turned black after finitely many applications of…

Combinatorics · Mathematics 2015-02-19 Linda Eroh , Cong X. Kang , Eunjeong Yi

The domatic number of a graph $G$ is the maximum number of pairwise disjoint dominating sets of $G$. We are interested in the LP-relaxation of this parameter, which is called the fractional domatic number of $G$. We study its extremal value…

Combinatorics · Mathematics 2025-08-28 Quentin Chuet , Hugo Demaret , Hoang La , François Pirot

A set $Z$ of vertices of a graph $G$ is a zero forcing set of $G$ if initially labeling all vertices in $Z$ with $1$ and all remaining vertices of $G$ with $0$, and then, iteratively and as long as possible, changing the label of some…

Combinatorics · Mathematics 2016-08-03 Michael Gentner , Dieter Rautenbach

A subset of vertices in a graph $G$ is considered a maximal dissociation set if it induces a subgraph with vertex degree at most 1 and it is not contained within any other dissociation sets. In this paper, it is shown that for $n\geq 3$,…

Combinatorics · Mathematics 2024-11-06 Junxia Zhang , Xiangyu Ren , Maoqun Wang

A subset $D\subseteq V_G$ is a dominating set of $G$ if every vertex in $V_G-D$ has a~neighbor in $D$, while $D$ is a paired-dominating set of $G$ if $D$ is a~dominating set and the subgraph induced by $D$ contains a perfect matching. A…

Combinatorics · Mathematics 2021-03-05 Michael A. Henning , Jerzy Topp

A graph $G$ is a DTDP-graph if it has a pair $(D,T)$ of disjoint sets of vertices of $G$ such that $D$ is a dominating set and $T$ is a total dominating set of $G$. Such graphs were studied in a number of research papers. In this paper we…

Combinatorics · Mathematics 2021-03-05 Michael A. Henning , Jerzy Topp

We study the $F$-decomposition threshold $\delta_F$ for a given graph $F$. Here an $F$-decomposition of a graph $G$ is a collection of edge-disjoint copies of $F$ in $G$ which together cover every edge of $G$. (Such an $F$-decomposition can…

Combinatorics · Mathematics 2019-03-14 Stefan Glock , Daniela Kühn , Allan Lo , Richard Montgomery , Deryk Osthus

A claw-free graph is a graph that does not contain $K_{1,3}$ as an induced subgraph, and a 2-factor is a 2-regular spanning subgraph of a graph. In 1997, Ryj\'{a}\v{c}ek introduced the closure concept of claw-free graphs, and Hamilton…

Combinatorics · Mathematics 2025-04-14 Masaki Kashima

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

A graph $G$ is called $k$-factor-critical if after deleting any $k$ vertices the remaining subgraph still has a perfect matching. Fan and Lin [Adv. in Appl. Math. 174 (2026) 103019] posed an adjacency spectral condition for a graph with…

Combinatorics · Mathematics 2026-05-27 Jiaxu Zhong , Yong Lu

A graph $G$ is called degree-truncated $k$-choosable if for every list assignment $L$ with $|L(v)| \ge \min\{d_G(v), k\}$ for each vertex $v$, $G$ is $L$-colourable. Richter asked whether every 3-connected non-complete planar graph is…

Combinatorics · Mathematics 2025-07-15 Huan Zhou , Jialu Zhu , Xuding Zhu

A 2-factor of a graph is a 2-regular spanning subgraph. For a graph $G$ and an independent set $I$ of $G$, let $\delta_G(I)$ denote the minimum degree of vertices contained in $I$. We show that (1) if every independent set $I$ of $G$…

Combinatorics · Mathematics 2025-03-25 Masaki Kashima

The degree sequence of a graph is the sequence of the degrees of its vertices. If $\pi$ is a degree sequence of a graph $G$, then $G$ is a realization of $\pi$ and $G$ realizes $\pi$. Determining when a sequence of positive integers is…

Combinatorics · Mathematics 2022-11-28 Jiyun Guo , Miao Fu , Yuqin Zhang , Haiyan Li

A graph $G$ of order $n$ is said to be $k$-factor-critical for integers $1\leq k < n$, if the removal of any $k$ vertices results in a graph with a perfect matching. $1$- and $2$-factor-critical graphs are the well-known factor-critical and…

Combinatorics · Mathematics 2022-07-08 Jing Guo , Heping Zhang

The dominating graph of a graph G is a graph whose vertices correspond to the dominating sets of G and two vertices are adjacent whenever their corresponding dominating sets differ in exactly one vertex. Studying properties of dominating…

Combinatorics · Mathematics 2022-12-12 Alireza Mofidi

Let $G$ be a graph and $\mathcal{F}$ a family of graphs. Define $\alpha_{\mathcal{F}}(G)$ as the maximum order of any induced subgraph of $G$ that belongs to the family $\mathcal{F}$. For the family $\mathcal{F}$ of graphs with…

Combinatorics · Mathematics 2026-05-12 Yair Caro , Randy Davila , Michael A. Henning , Ryan Pepper

A total dominating set of a graph $G$ is a set $D$ of vertices of $G$ such that every vertex of $G$ has a neighbor in $D$. A locating-total dominating set of $G$ is a total dominating set $D$ of $G$ with the additional property that every…

Combinatorics · Mathematics 2016-07-25 Florent Foucaud , Michael A. Henning

A graph $G$ is $k$-vertex-critical if $\chi(G)=k$, but $\chi(G')<k$ for every proper induced subgraph $G'$ of $G$. For a family of graphs $\mathcal{F}$, $G$ is $\mathcal{F}$-free if no graph $F \in \mathcal{F}$ is an induced subgraph of…

Combinatorics · Mathematics 2025-12-24 Yidong Zhou , Jorik Jooken , Baoyuan Shan , Jan Goedgebeur , Shenwei Huang

In this paper, our goal is to characterize two graph classes based on the properties of minimal vertex (edge) separators. We first present a structural characterization of graphs in which every minimal vertex separator is a stable set. We…

Discrete Mathematics · Computer Science 2011-03-16 Mrinal Kumar , Gaurav Maheswari , N. Sadagopan