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Jord\'an and Tanigawa recently introduced the $d$-dimensional algebraic connectivity $a_d(G)$ of a graph $G$. This is a quantitative measure of the $d$-dimensional rigidity of $G$ which generalizes the well-studied notion of spectral…

Combinatorics · Mathematics 2023-04-05 Alan Lew , Eran Nevo , Yuval Peled , Orit E. Raz

We apply eigenvalue interlacing techniques for obtaining lower and upper bounds for the sums of Laplacian eigenvalues of graphs, and characterize equality. This leads to generalizations of, and variations on theorems by Grone, and Grone and…

Spectral Theory · Mathematics 2013-11-20 A. Abiad , M. A. Fiol , W. H. Haemers , G. Perarnau

Recently, it has been proposed that the natural connectivity can be used to efficiently characterise the robustness of complex networks. Natural connectivity quantifies the redundancy of alternative routes in a network by evaluating the…

Statistical Mechanics · Physics 2010-09-20 Jun Wu , Mauricio Barahona , Yuejin Tan , Hongzhong Deng

For minimally $k$-connected graphs on $n$ vertices, Mader proved a tight lower bound for the number $|V_k|$ of vertices of degree $k$ in dependence on $n$ and $k$. Oxley observed 1981 that in many cases a considerably better bound can be…

Combinatorics · Mathematics 2016-03-31 Jens M. Schmidt

In this paper, we obtain lower bounds for the domination numbers of connected graphs with girth at least $7$. We show that the domination number of a connected graph with girth at least $7$ is either $1$ or at least…

Discrete Mathematics · Computer Science 2016-01-05 Yinglei Song

The Cheeger constant of a graph is the smallest possible ratio between the size of a subgraph and the size of its boundary. It is well known that this constant must be at least $\frac{\lambda_1}{2}$, where $\lambda_1$ is the smallest…

Combinatorics · Mathematics 2019-09-19 Jack Koolen , Greg Markowsky , Zhi Qiao

Let $\alpha'$ and $\mu_i$ denote the matching number of a non-empty simple graph $G$ with $n$ vertices and the $i$-th smallest eigenvalue of its Laplacian matrix, respectively. In this paper, we prove a tight lower bound $$\alpha' \ge…

Combinatorics · Mathematics 2021-11-16 Xiaofeng Gu , Muhuo Liu

Recently, the stability of graph filters has been studied as one of the key theoretical properties driving the highly successful graph convolutional neural networks (GCNs). The stability of a graph filter characterizes the effect of…

Signal Processing · Electrical Eng. & Systems 2021-10-15 Hoang-Son Nguyen , Yiran He , Hoi-To Wai

In this paper a relationship is established between the domination game and minimal edge cuts. It is proved that the game domination number of a connected graph can be bounded above in terms of the size of minimal edge cuts. In particular,…

Combinatorics · Mathematics 2018-10-25 Sandi Klavžar , Douglas F. Rall

The $\ell$-component connectivity (or $\ell$-connectivity for short) of a graph $G$, denoted by $\kappa_\ell(G)$, is the minimum number of vertices whose removal from $G$ results in a disconnected graph with at least $\ell$ components or a…

Discrete Mathematics · Computer Science 2021-05-25 Jou-Ming Chang , Kung-Jui Pai , Ro-Yu Wu , Jinn-Shyong Yang

The conditional diagnosability and the 2-extra connectivity are two important parameters to measure ability of diagnosing faulty processors and fault-tolerance in a multiprocessor system. The conditional diagnosability $t_c(G)$ of $G$ is…

Combinatorics · Mathematics 2015-08-11 Rong-Xia Hao , Zeng-Xian Tian , Jun-Ming Xu

This paper provides a construction method of the nearest graph Laplacian to a matrix identified from measurement data of graph Laplacian dynamics that include biochemical systems, synchronization systems, and multi-agent systems. We…

Optimization and Control · Mathematics 2018-06-20 Kazuhiro Sato

The Erd\H{o}s-Gallai Theorem states that every graph of average degree more than $l-2$ contains a path of order $l$ for $l\ge 2$. In this paper, we obtain a stability version of the Erd\H{o}s-Gallai Theorem in terms of minimum degree. Let…

Combinatorics · Mathematics 2019-08-05 Ming-Zhu Chen , Xiao-Dong Zhang

For any real $\alpha \in [0,1]$, Nikiforov defined the $A_\alpha$-matrix of a graph $G$ as $A_\alpha(G)=\alpha D(G)+(1-\alpha)A(G)$, where $A(G)$ and $D(G)$ are the adjacency matrix and the diagonal matrix of vertex degrees of $G$,…

Combinatorics · Mathematics 2023-01-10 Jiayu Lou , Ligong Wang , Ming Yuan

Over the past half century, the rigidity of graphs in $R^2$ has aroused a great deal of interest. Lov\'{a}sz and Yemini (1982) proved that every $6$-connected graph is rigid in $R^2$. Jackson and Jord\'{a}n (2005) provided a similar…

Combinatorics · Mathematics 2022-05-27 Dandan Fan , Xueyi Huang , Huiqiu Lin

Let $G$ be an edge-colored connected graph. A path $P$ in $G$ is called a distance $\ell$-proper path if no two edges of the same color appear with fewer than $\ell$ edges in between on $P$. The graph $G$ is called $(k,\ell)$-proper…

Combinatorics · Mathematics 2016-06-22 Xueliang Li , Colton Magnant , Meiqin Wei , Xiaoyu Zhu

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

The Laplacian energy of a graph is the sum of the distances of the eigenvalues of the Laplacian matrix of the graph to the graph's average degree. The maximum Laplacian energy over all graphs on $n$ nodes and $m$ edges is conjectured to be…

Combinatorics · Mathematics 2017-04-05 Christoph Helmberg , Vilmar Trevisan

We establish a strong, geometric lower bound on the (sequential) topological complexity of the unordered configuration spaces of a general graph. As an application, we show that, for most graphs, the topological complexity eventually…

Algebraic Topology · Mathematics 2026-02-05 Ben Knudsen

We introduce and study a generalization of conformal rigidity for graphs. A graph is $k$-conformally rigid if the uniform edge weights simultaneously maximize the sum of the $k$ smallest nontrivial Laplacian eigenvalues and minimize the sum…

Combinatorics · Mathematics 2026-05-12 Henrique Assumpção , Gabriel Coutinho , Chris Godsil