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In 2018, the concept of a fort in graph theory was introduced as a non-empty subset of vertices satisfying the condition that no vertex outside the set has exactly one neighbor in the set. Since then, forts have played a significant role in…

组合数学 · 数学 2026-03-12 Thomas R. Cameron , Kelvin Li

In 2018, a fort of a graph was introduced as a non-empty subset of vertices in which no vertex outside of the set has exactly one neighbor in the set. Since then, forts have been used to characterize zero forcing sets, model the zero…

组合数学 · 数学 2024-04-10 Paul Becker , Thomas R. Cameron , Derek Hanely , Boon Ong , Joseph P. Previte

In this paper we begin the study of well-failed graphs, that is, graphs in which every maximal failed zero forcing set is a maximum failed zero forcing set, or equivalently, in which every minimal fort is a minimum fort. We characterize…

组合数学 · 数学 2025-02-03 Bonnie Jacob

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…

离散数学 · 计算机科学 2026-05-12 Samuel German

In 2018, forts were defined as non-empty subsets of vertices in a graph where no vertex outside the set has exactly one neighbor in the set. Forts have since been used to characterize zero forcing sets, model zero forcing as an integer…

组合数学 · 数学 2025-07-16 Boris Brimkov , Thomas R. Cameron , Owen Grubbs

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…

组合数学 · 数学 2023-12-25 Cheryl Grood , Ruth Haas , Bonnie Jacob , Erika King , Shahla Nasserasr

For any simple graph $G$ on $n$ vertices, the (positive semi-definite) minimum rank of $G$ is defined to be the smallest possible rank among all (positive semi-definite) real symmetric $n\times n$ matrices whose entry in position $(i,j)$,…

组合数学 · 数学 2013-12-02 Fatemeh Alinaghipour Taklimi

Given a graph $G$ and a real number $0\le p\le 1$, we define the random set $B_p(G)\subset V(G)$ by including each vertex independently and with probability $p$. We investigate the probability that the random set $B_p(G)$ is a zero forcing…

组合数学 · 数学 2022-08-30 Bryan Curtis , Luyining Gan , Jamie Haddock , Rachel Lawrence , Sam Spiro

A forcing set $S$ in a combinatorial problem is a set of elements such that there is a unique solution that contains all the elements in $S$. An anti-forcing set is the symmetric concept: a set $S$ of elements is called an anti-forcing set…

数据结构与算法 · 计算机科学 2025-12-18 Tatsuya Gima , Yasuaki Kobayashi , Yota Otachi , Takumi Sato

The zero forcing number and the positive zero forcing number of a graph are two graph parameters that arise from two types of graph colourings. The zero forcing number is an upper bound on the minimum number of induced paths in the graph,…

组合数学 · 数学 2013-11-28 Fatemeh Alinaghipour Taklimi , Shaun Fallat , Karen Meagher

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…

组合数学 · 数学 2023-03-13 Emelie Curl , Shaun Fallat , Ryan Moruzzi , Carolyn Reinhart , Derek Young

We give an algorithm that finds a zero forcing set which approximates the optimal size by a factor of $\text{pw}(G)+1$, where $\text{pw}(G)$ is the pathwidth of $G$. Starting from a path decomposition, the algorithm runs in $O(nm)$ time,…

组合数学 · 数学 2024-02-15 Ben Cameron , Jeannette Janssen , Rogers Matthew , Zhiyuan Zhang

We propose the conjecture that every tree with order $n$ at least $2$ and total domination number $\gamma_t$ has at most $\left(\frac{n-\frac{\gamma_t}{2}}{\frac{\gamma_t}{2}}\right)^{\frac{\gamma_t}{2}}$ minimum total dominating sets. As a…

组合数学 · 数学 2023-06-22 Michael A. Henning , Elena Mohr , Dieter Rautenbach

This paper begins the study of reconfiguration of zero forcing sets, and more specifically, the zero forcing graph. Given a base graph $G$, its zero forcing graph, $\mathscr{Z}(G)$, is the graph whose vertices are the minimum zero forcing…

组合数学 · 数学 2020-09-02 Jesse Geneson , Ruth Haas , Leslie Hogben

An algorithm is proposed for constructing directed spanning forests of the minimum weight, in which the maximum possible degree of affinity between the minimum forests is preserved when the number of trees changes. The correctness of the…

组合数学 · 数学 2025-02-18 Vasily Buslov

We introduce a graph partitioning problem motivated by computational topology and propose two algorithms that produce approximate solutions. Specifically, given a weighted, undirected graph $G$ and a positive integer $k$, we desire to find…

组合数学 · 数学 2019-07-04 Abdel-Rahman Madkour , Phillip Nadolny , Matthew Wright

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…

组合数学 · 数学 2022-04-18 Boris Brimkov , Joshua Carlson

The zero forcing number Z(G), which is the minimum number of vertices in a zero forcing set of a graph G, is used to study the maximum nullity / minimum rank of the family of symmetric matrices described by G. It is shown that for a…

The zero forcing number is a graph invariant introduced to study the minimum rank of the graph. In 2008, Aazami proved the NP-hardness of computing the zero forcing number of a simple undirected graph. We complete this NP-hardness result by…

离散数学 · 计算机科学 2015-06-09 Maguy Trefois , Jean-Charles Delvenne

We prove a lower bound on the number of spanning two-forests in a graph, in terms of the number of vertices, edges, and spanning trees. This implies an upper bound on the average cut size of a random two-forest. The main tool is an identity…

组合数学 · 数学 2023-08-09 Harry Richman , Farbod Shokrieh , Chenxi Wu
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