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The signless Laplacian spectral radius has emerged as a crucial spectral parameter in network science. This paper establishes new extremal results in spectral graph theory by investigating the signless Laplacian spectral radius ($Q$-index)…

Combinatorics · Mathematics 2026-01-27 Zhe Wei , Zhenzhen Lou , Changxiang He

Consider a semigraph $G=(V,\,E)$; in this paper, we study the eigenvalues of the Laplacian matrix of $G$. We show that the Laplacian of $G$ is positive semi-definite, and $G$ is connected if and only if $\lambda_2 >0.$ Along the similar…

Combinatorics · Mathematics 2023-07-10 Pralhad M. Shinde

In this paper, we introduce a generalization of corona of graphs. This construction generalizes the generalized corona of graphs (consequently, the corona of graphs), the cluster of graphs, the corona-vertex subdivision graph of graphs and…

Combinatorics · Mathematics 2020-08-13 R. Rajkumar , M. Gayathri

This note introduces a result on the location of eigenvalues, i.e., the spectrum, of the Laplacian for a family of undirected graphs with self-loops. We extend on the known results for the spectrum of undirected graphs without self-loops or…

Optimization and Control · Mathematics 2015-06-09 Behcet Acikmese

Classical graph matching aims to find a node correspondence between two unlabeled graphs of known topologies. This problem has a wide range of applications, from matching identities in social networks to identifying similar biological…

Signal Processing · Electrical Eng. & Systems 2024-10-28 Hang Liu , Anna Scaglione , Hoi-To Wai

Signed networks are graphs whose edges are labelled with either a positive or a negative sign, and can be used to capture nuances in interactions that are missed by their unsigned counterparts. The concept of balance in signed graph theory…

Social and Information Networks · Computer Science 2020-02-04 Bruno Ordozgoiti , Antonis Matakos , Aristides Gionis

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…

Combinatorics · Mathematics 2014-08-26 Nathan Reff

Let A be a graph type and B an equivalence relation on a group $G$. Let $[g]$ be the equivalence class of $g$ with respect to the equivalence relation B. The B superA graph of $G$ is an undirected graph whose vertex set is $G$ and two…

Combinatorics · Mathematics 2025-09-24 G. Arunkumar , Peter J. Cameron , R. Ganeshbabu , Rajat Kanti Nath

We give some graph theoretical formulas for the trace $Tr_k(\mathbb {T})$ of a tensor $\mathbb {T}$ which do not involve the differential operators and auxiliary matrix. As applications of these trace formulas in the study of the spectra of…

Spectral Theory · Mathematics 2013-07-23 Jia-Yu Shao , Liqun Qi , Shenglong Hu

Let \Gamma be a signed graph and let A(\Gamma) be the adjacency matrix of \Gamma. The nullity of \Gamma is the multiplicity of eigenvalue zero in the spectrum of A(\Gamma). In this paper we characterize the signed graphs of order n with…

Combinatorics · Mathematics 2014-09-19 Yi-Zheng Fan , Wen-Xue Du , Chun-Long Dong

Spectral geometric methods have brought revolutionary changes to the field of geometry processing. Of particular interest is the study of the Laplacian spectrum as a compact, isometry and permutation-invariant representation of a shape.…

Graphics · Computer Science 2023-03-13 Robin Magnet , Maks Ovsjanikov

The zero-divisor graph $\Gamma(R)$ of a ring $R$ is a graph with nonzero zero-divisors of $R$ as vertices and distinct vertices $x,y$ are adjacent if $xy=0$ or $yx=0$. We provide an equivalence relation on a ring $R$ and express $\Gamma(R)$…

Spectral Theory · Mathematics 2022-04-01 Krishnat D. Masalkar , Anil Khairnar , Anita Lande , Avinash Patil

Signed graphs have their edges labeled either as positive or negative. Here we introduce two types of signed distance matrix for signed graphs. We characterize balance in signed graphs using these matrices and we obtain explicit formulae…

Combinatorics · Mathematics 2021-06-21 Shahul Hameed K , Shijin T , Soorya P , Germina K A , Thomas Zaslavsky

A signed graph $\Gamma$ is said to be determined by its spectrum if every signed graph with the same spectrum as $\Gamma$ is switching isomorphic with $\Gamma$. Here it is proved that the path $P_n$, interpreted as a signed graph, is…

Combinatorics · Mathematics 2018-05-11 Saieed Akbari , Willem H. Haemers , Hamid Reza Maimani , Leila Parsaei Majd

It is reported that dynamical systems over digraphs have superior performance in terms of system damping and tolerance to time delays if the underlying graph Laplacian has a purely real spectrum. This paper investigates the topological…

Optimization and Control · Mathematics 2025-08-08 Tianhao Yu , Shenglu Wang , Mengqi Xue , Yue Song , David J. Hill

A graph $\Gamma$ is called $G$-symmetric if it admits $G$ as a group of automorphisms acting transitively on the set of ordered pairs of adjacent vertices. We give a classification of $G$-symmetric graphs $\Gamma$ with $V(\Gamma)$ admitting…

Group Theory · Mathematics 2017-06-19 Teng Fang , Xin Gui Fang , Binzhou Xia , Sanming Zhou

In this paper, we completely classify the connected non-bipartite graphs with integral signless Laplacian eigenvalues at most 6.

Combinatorics · Mathematics 2025-03-20 Semin Oh , Jeong Rye Park , Jongyook Park , Yoshio Sano

A signed graph is one that features two types of edges: positive and negative. Balanced signed graphs are those in which all cycles contain an even number of positive edges. In the adjacency matrix of a signed graph, entries can be $0$,…

Combinatorics · Mathematics 2024-08-15 Cristian M. Conde , Ezequiel Dratman , Luciano N. Grippo

For a given hypergraph, an orientation can be assigned to the vertex-edge incidences. This orientation is used to define the adjacency and Laplacian matrices. In addition to studying these matrices, several related structures are…

Combinatorics · Mathematics 2015-09-08 Nathan Reff

In this paper, we present some spectral sufficient conditions for a graph to be Hamilton-connected in terms of the spectral radius or signless Laplacian spectral radius of the graph. Our results improve some previous work.

Combinatorics · Mathematics 2017-11-09 Qiannan Zhou , Ligong Wang , Yong Lu
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