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This survey is two-fold. We first report new progress on the spectral extremal results on the Tur\'{a}n type problems in graph theory. More precisely, we shall summarize the spectral Tur\'{a}n function in terms of the adjacency spectral…

Combinatorics · Mathematics 2022-05-13 Yongtao Li , Weijun Liu , Lihua Feng

In this article we consider the spectrum of a Laplacian matrix, also known as the Markov matrix, under the independence assumption. We assume that the entries have a variance profile. Motivated by recent works on generalized Wigner matrices…

Probability · Mathematics 2021-07-13 Anirban Chatterjee , Rajat Subhra Hazra

A finite discrete graph is turned into a quantum (metric) graph once a finite length is assigned to each edge and the one-dimensional Laplacian is taken to be the operator. We study the dependence of the spectral gap (the first positive…

Mathematical Physics · Physics 2018-03-28 Ram Band , Guillaume Lévy

Laplace operators on finite compact metric graphs are considered under the assumption that matching conditions at graph vertices are of $\delta$ and $\delta'$ types. Assuming rational independence of edge lengths, necessary and sufficient…

Spectral Theory · Mathematics 2015-12-09 Yulia Ershova , Irina I. Karpenko , Alexander V. Kiselev

A graph's spectral wavelet signature determines a filtration, and consequently an associated set of extended persistence diagrams. We propose a framework that optimises the choice of wavelet for a dataset of graphs, such that their…

Signal Processing · Electrical Eng. & Systems 2023-06-28 Ka Man Yim , Jacob Leygonie

This paper investigates spectral properties of the deformed Laplacian matrix, which merges the Laplacian and signless Laplacian matrices of a graph through a one-parameter family of matrices. We present general results on the eigenvalues of…

Combinatorics · Mathematics 2025-12-04 Roberto C. Díaz , Elismar R. Oliveira , Vilmar Trevisan

A propeller graph is obtained from an $\infty$-graph by attaching a path to the vertex of degree four, where an $\infty$-graph consists of two cycles with precisely one common vertex. In this paper, we prove that all propeller graphs are…

Combinatorics · Mathematics 2014-02-18 Xiaogang Liu , Sanming Zhou

In this paper, we introduce a matrix for a mixed graph, called the integrated adjacency matrix. This matrix uniquely determines a mixed graph, as long as the indices of the matrix are specified. Additionally, we associate an (undirected)…

Combinatorics · Mathematics 2025-11-27 G. Kalaivani , R. Rajkumar

We characterize the spectrum of the Laplacian of graphs composed of one or two finite or infinite chains connected to a complete graph. We show the existence of localized eigenvectors of two types, eigenvectors that vanish exactly outside…

Spectral Theory · Mathematics 2020-02-21 J. -G. Caputo , G. Cruz-Pacheco , A. Knippel , P. Panayotaros

In this article, we develop a perturbative technique to construct families of non-isomorphic discrete graphs which are isospectral for the standard (also called normalised) Laplacian and its signless version. We use vertex contractions as a…

Combinatorics · Mathematics 2022-07-11 Fernando Lledó , John S. Fabila-Carrasco , Olaf Post

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

A metrized graph is a compact singular 1-manifold endowed with a metric. A given metrized graph can be modelled by a family of weighted combinatorial graphs. If one chooses a sequence of models from this family such that the vertices become…

Classical Analysis and ODEs · Mathematics 2007-05-23 X. W. C. Faber

Two signed graphs are called switching isomorphic if one of them is isomorphic to a switching equivalent of the other. To determine the number of switching non-isomorphic signed graphs on a specific graph, we will establish a method based…

Combinatorics · Mathematics 2019-09-17 Yousef Bagheri , Alireza Moghadamfar , Farzaneh Ramezani

A sign is introduced in the usual Laplacian on graphs and the corresponding analogue of the isoperimetric constant for this Laplacian is presented, i.e. a geometric quantity which enables to bound from above and below the first eigenvalue.…

Differential Geometry · Mathematics 2019-10-22 Antoine Gournay

We give a construction of a family of (weighted) graphs that are pairwise cospectral with respect to the normalized Laplacian matrix, or equivalently probability transition matrix. This construction can be used to form pairs of cospectral…

Combinatorics · Mathematics 2015-07-08 Steve Butler , Kristin Heysse

The index of a signed graph is the largest eigenvalue of its adjacency matrix. For positive integers $n$ and $m\le n^2/4$, we determine the maximal index of complete signed graphs with $n$ vertices and $m$ negative edges. This settles (the…

Combinatorics · Mathematics 2021-05-04 Ebrahim Ghorbani , Arezoo Majidi

The line graph of a graph with signed edges carries vertex signs. A vertex-signed graph is consistent if every circle (cycle, circuit) has positive vertex-sign product. Acharya, Acharya, and Sinha recently characterized line-consistent…

Combinatorics · Mathematics 2021-06-21 Daniel C. Slilaty , Thomas Zaslavsky

We study two different types of gluing for graphs: interface (obtained by choosing a common subgraph as the gluing component) and bridge gluing (obtained by adding a set of edges to the given subgraphs). We introduce formulae for computing…

Mathematical Physics · Physics 2018-05-07 Ivan Contreras , Michael Toriyama , Chengzheng Yu

The spectra of signed matrices have played a fundamental role in social sciences, graph theory, and control theory. In this work, we investigate the computational problems of identifying symmetric signings of matrices with natural spectral…

Discrete Mathematics · Computer Science 2017-07-25 Charles Carlson , Karthekeyan Chandrasekaran , Hsien-Chih Chang , Alexandra Kolla

In this article, we generate large families of non-isomorphic and signless Lalacian cospectral graphs using partial transpose on graphs. Our constructions are significantly powerful. More than $70\%$ of non-isomorphic signless-Laplacian…

Combinatorics · Mathematics 2018-08-14 Supriyo Dutta