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We investigate generalized inverses of matrices associated with two classes of digraphs: double star digraphs and D-linked stars digraphs. For double star digraphs, we determine the Drazin index and derive explicit formulas for the Drazin…

组合数学 · 数学 2025-10-28 Cláudia M. Araújo , Faustino A. Maciala , Pedro Patrício

In this paper a new graph invariant based on the minimal hitting set problem is introduced. It is shown that it represents a tight lower bound for the doubly metric dimension of a graph. Exact values of new invariant for paths, stars,…

组合数学 · 数学 2023-10-11 Jozef Kratica , Vera Kovačević-Vujčić , Mirjana Čangalović

Let $T$ be a tree with $n$ vertices. To each edge of $T$, we assign a weight which is a positive definite matrix of some fixed order, say, $s$. Let $D_{ij}$ denote the sum of all the weights lying in the path connecting the vertices $i$ and…

组合数学 · 数学 2019-12-12 Balaji Ramamurthy , Ravindra Bapat , Shivani Goel

A complex unit gain graph is a graph where each orientation of an edge is given a complex unit, which is the inverse of the complex unit assigned to the opposite orientation. We extend some fundamental concepts from spectral graph theory to…

组合数学 · 数学 2014-08-26 Nathan Reff

M. Aouchiche and P. Hansen proposed the distance Laplacian and the distance signless Laplacian of a connected graph [Two Laplacians for the distance matrix of a graph, LAA 439 (2013) 21{33]. In this paper, we obtain three theorems on the…

组合数学 · 数学 2013-08-16 Wenxi Hong , Lihua You

Let $\Gamma$ be a locally finite graph, $L$ the normalized Laplacian of $\Gamma$. If $\Gamma$ is uniformy locally finite, i.e. if each vertex has no more than $d$ adjacent vertices, then the matrix of $L$ (with respect to the standard…

组合数学 · 数学 2018-08-14 Vladimir Manuilov

The enhanced power graph of a group $G$ is a simple undirected graph with vertex set $G$ and two vertices are adjacent if they belong to same cyclic subgroup. In this paper, we study distant properties and detour distant properties such as…

群论 · 数学 2021-08-31 Parveen , Sandeep Dalal , Jitender Kumar

We study the properties of several proximity measures for the vertices of weighted multigraphs and multidigraphs. Unlike the classical distance for the vertices of connected graphs, these proximity measures are applicable to weighted…

组合数学 · 数学 2007-05-23 Pavel Chebotarev , Elena Shamis

We consider a distance-regular graph $\Gamma=(X, \mathcal R)$ called the bilinear forms graph $H_q(D,N-D)$; we assume $N>2D\geq 6$ and $q \not=2$. We show that $\Gamma$ satisfies the following strengthened version of the balanced set…

组合数学 · 数学 2026-01-28 Paul Terwilliger , Jason Williford

Manifold submetries of the round sphere are a class of partitions of the round sphere that generalizes both singular Riemannian foliations, and the orbit decompositions by the orthogonal representations of compact groups. We exhibit a…

微分几何 · 数学 2020-02-10 Ricardo A. E. Mendes , Marco Radeschi

We extend the concept of the m-weak group MP inverse of a square matrix to a rectangular matrix, called the W-weighted m-weak group MP inverse, which also unifies the W-weighted weak core inverse and W-weighted DMP inverse. Some properties,…

泛函分析 · 数学 2024-11-05 Jiale Gao , Kezheng Zuo , Qing-Wen Wang

In graph signal processing, data samples are associated to vertices on a graph, while edge weights represent similarities between those samples. We propose a convex optimization problem to learn sparse well connected graphs from data. We…

信号处理 · 电气工程与系统科学 2020-04-21 Eduardo Pavez , Antonio Ortega

The Laplacian spread of a graph is the difference between the largest eigenvalue and the second-smallest eigenvalue of the Laplacian matrix of the graph. We find that the class of strongly regular graphs attains the maximum of largest…

组合数学 · 数学 2014-11-25 Fan-Hsuan Lin , Chih-wen Weng

The edit distance between two graphs is a widely used measure of similarity that evaluates the smallest number of vertex and edge deletions/insertions required to transform one graph to another. It is NP-hard to compute in general, and a…

数据结构与算法 · 计算机科学 2019-04-22 Utkan Onur Candogan , Venkat Chandrasekaran

We demonstrate how the inverse scattering problem of a quantum star graph can be solved by means of diagonalization of Hermitian unitary matrix when the vertex coupling is of the scale invariant (or F\"ul\H{o}p-Tsutsui) form. This enables…

量子物理 · 物理学 2011-09-22 Taksu Cheon , Pavel Exner , Ondrej Turek

We provide a complete description of important geometric invariants of the Laplacian lattice of a multigraph under the distance function induced by a regular simplex, namely Voronoi Diagram, Delaunay Triangulation, Delaunay Polytope and its…

组合数学 · 数学 2011-12-01 Madhusudan Manjunath

How to draw the vertices of a complete multipartite graph $G$ on different points of a bounded $d$-dimensional integer grid, such that the sum of squared distances between vertices of $G$ is (i) minimized or (ii) maximized? For both…

离散数学 · 计算机科学 2018-08-29 Ruy Fabila-Monroy , Carlos Hidalgo-Toscano , Clemens Huemer , Dolores Lara , Dieter Mitsche

Acyclic digraphs are the underlying representation of Bayesian networks, a widely used class of probabilistic graphical models. Learning the underlying graph from data is a way of gaining insights about the structural properties of a…

机器学习 · 统计学 2022-05-06 Jack Kuipers , Giusi Moffa

The characterization of distance-regular Cayley graphs originated from the problem of identifying strongly regular Cayley graphs, or equivalently, regular partial difference sets. In this paper, a classification of distance-regular Cayley…

组合数学 · 数学 2022-03-25 Xueyi Huang , Kinkar Chandra Das , Lu Lu

Stress models are a promising approach for graph drawing. They minimize the weighted sum of the squared errors of the Euclidean and desired distances for each node pair. The desired distance typically uses the graph-theoretic distances…

数据结构与算法 · 计算机科学 2024-03-26 Yosuke Onoue