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It is known that every multigraph with an even number of edges has an even orientation (i.e., all indegrees are even). We study parity constrained graph orientations under additional constraints. We consider two types of constraints for a…

计算几何 · 计算机科学 2012-03-27 Sarah Cannon , Mashhood Ishaque , Csaba Tóth

The cyclic matching sequenceability of a simple graph $G$, denoted $\mathrm{cms}(G)$, is the largest integer $s$ for which there exists a cyclic ordering of the edges of $G$ so that every set of $s$ consecutive edges forms a matching. In…

组合数学 · 数学 2021-06-23 Daniel Horsley , Adam Mammoliti

Zero forcing is a process on a graph that colors vertices blue by starting with some of the vertices blue and applying a color change rule. Throttling minimizes the sum of the size of the initial blue vertex set and the number of the time…

While a number of bounds are known on the zero forcing number $Z(G)$ of a graph $G$ expressed in terms of the order of a graph and maximum or minimum degree, we present two bounds that are related to the (upper) total domination number…

组合数学 · 数学 2023-10-12 Boštjan Brešar , María Gracia Cornet , Tanja Dravec , Michael Henning

An antimagic labeling of a graph $G$ is an injection from $E(G)$ to $\{1,2,\dots,|E(G)|\}$ such that all vertex sums are pairwise distinct, where the vertex sum at vertex $u$ is the sum of the labels assigned to edges incident to $u$. A…

组合数学 · 数学 2024-05-09 Antoni Lozano , Mercè Mora , Carlos Seara , Joaquín Tey

The concept of antimagic labelings of a graph is to produce distinct vertex sums by labeling edges through consecutive numbers starting from one. A long-standing conjecture is that every connected graph, except a single edge, is antimagic.…

组合数学 · 数学 2019-05-21 Fei-Huang Chang , Hong-Bin Chen , Wei-Tian Li , Zhishi Pan

Let $G$ be a graph and $A$ be its adjacency matrix. A graph $G$ is invertible if its adjacency matrix $A$ is invertible and the inverse of $G$ is a weighted graph with adjacency matrix $A^{-1}$. A signed graph $(G,\sigma)$ is a weighted…

组合数学 · 数学 2023-03-23 Isaiah Osborne , Dong Ye

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

It is shown that for a given infinite graph $G$ on countably many vertices, and a compact, infinite set of real numbers $\Lambda$ there is a real symmetric matrix $A$ whose graph is $G$ and its spectrum is $\Lambda$. Moreover, the set of…

谱理论 · 数学 2016-10-06 Keivan Hassani Monfared , Ehssan Khanmohammadi

It is well known that a graph $G$ has a symmetric spectrum if and only if it is bipartite, a signed graph $\Gamma=(G,\sigma)$ has a symmetric spectrum if $G$ is bipartite. However, there exists a spectrally symmetric signed graph…

组合数学 · 数学 2025-05-02 Deqiong Li , Qiongxiang Huang

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…

组合数学 · 数学 2025-08-12 Thomas R. Cameron , Jonad Pulaj

Given a graph $G=(V,E)$ and a colouring $f:E\mapsto \mathbb N$, the induced colour of a vertex $v$ is the sum of the colours at the edges incident with $v$. If all the induced colours of vertices of $G$ are distinct, the colouring is called…

组合数学 · 数学 2014-09-15 Tom Eccles

We give an upper bound on the number of perfect matchings in an undirected simple graph $G$ with an even number of vertices, in terms of the degrees of all the vertices in $G$. This bound is sharp if $G$ is a union of complete bipartite…

组合数学 · 数学 2008-03-07 Shmuel Friedland

For a graph $G$ with $n$ vertices, let $\nu(G)$ and $A(G)$ denote the matching number and adjacency matrix of $G$, respectively. The permanental polynomial of $G$ is defined as $\pi(G,x)={\rm per}(Ix-A(G))$. The permanental nullity of $G$,…

组合数学 · 数学 2016-03-11 Tingzeng Wu , Hong-Jian Lai

A dynamic coloring of the vertices of a graph $G$ starts with an initial subset $F$ of colored vertices, with all remaining vertices being non-colored. At each time step, a colored vertex with exactly one non-colored neighbor forces this…

组合数学 · 数学 2019-03-21 Meysam Alishahi , Elahe Rezaei-Sani , Elahe Sharifi

The concept of zero forcing is extended from graphs to uniform hypergraphs in analogy with the way zero forcing was defined as an upper bound for the maximum nullity of the family of symmetric matrices whose nonzero pattern of entries is…

组合数学 · 数学 2018-08-30 Leslie Hogben

In a variety of contexts, we prove that singular continuous spectrum is generic in the sense that for certain natural complete metric spaces of operators, those with singular spectrum are a dense $G_\delta$.

A total coloring of a graph $G$ is a coloring of its vertices and edges such that no adjacent vertices, edges, and no incident vertices and edges obtain the same color. An interval total $t$-coloring of a graph $G$ is a total coloring of…

组合数学 · 数学 2014-08-12 Petros A. Petrosyan , Nerses A. Khachatryan

Given a graph $G$, the zero forcing number of $G$, $Z(G)$, is the smallest cardinality of any set $S$ of vertices on which repeated applications of the forcing rule results in all vertices being in $S$. The forcing rule is: if a vertex $v$…

组合数学 · 数学 2022-09-21 Aidan Johnson , Andrew E. Vick , Darren A. Narayan

Let $G=(V(G),E(G))$ be a graph with vertex set $V(G)$ and edge set $E(G)$. The resistance distance $R_G(x,y)$ between two vertices $x,y$ of $G$ is defined to be the effective resistance between the two vertices in the corresponding…

组合数学 · 数学 2024-03-12 Si-Ao Xu , Huan Zhou , Xiang-Feng Pan