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A complex unit gain graph ($ \mathbb{T} $-gain graph), $ \Phi=(G, \varphi) $ is a graph where the gain function $ \varphi $ assigns a unit complex number to each orientation of an edge of $ G $ and its inverse is assigned to the opposite…

Combinatorics · Mathematics 2023-12-29 Aniruddha Samanta , M. Rajesh Kannan

We introduce a hypergraph matrix, named the unified matrix, and use it to represent the hypergraph as a graph. We show that the unified matrix of a hypergraph is identical to the adjacency matrix of the associated graph. This enables us to…

Combinatorics · Mathematics 2024-11-12 R. Vishnupriya , R. Rajkumar

We investigate spectral properties of quantum graphs in the form of a periodic chain of rings with a connecting link between each adjacent pair, assuming that wave functions at the vertices are matched through conditions manifestly…

Mathematical Physics · Physics 2022-07-12 Marzieh Baradaran , Pavel Exner , Milos Tater

Let $G$ be a connected graph with vertex set $V(G)=\{v_{1},v_{2},...,v_{n}\}$. The distance matrix $D(G)=(d_{ij})_{n\times n}$ is the matrix indexed by the vertices of $G,$ where $d_{ij}$ denotes the distance between the vertices $v_{i}$…

Combinatorics · Mathematics 2018-01-30 Ruifang Liu , Jie Xue

Graph operations or products play an important role in complex networks. In this paper, we study the properties of $q$-subdivision graphs, which have been applied to model complex networks. For a simple connected graph $G$, its…

Combinatorics · Mathematics 2020-02-25 Yibo Zeng , Zhongzhi Zhang

A knot $K$ is called $n$-adjacent to a knot $K'$ if there is a set of $n$ crossing circles $\mathcal C$ in $K$ so that a generalized crossing change at any nonempty subset of crossings in $\mathcal C$ yields $K'$. In this paper, the authors…

Geometric Topology · Mathematics 2026-05-11 Marion Campisi , Brandy Doleshal , Eric Staron

A graph $G$ is said to be determined by the spectrum of its Laplacian matrix (DLS) if every graph with the same spectrum is isomorphic to $G$. van Dam and Haemers (2003) conjectured that almost all graphs have this property, but that is…

Combinatorics · Mathematics 2019-03-28 A. Z. Abdian , A. R. Ashrafi , L. W. Beineke , M. R. Oboudi

A $\mathbb{T}$-gain graph, $\Phi = (G, \varphi)$, is a graph in which the function $\varphi$ assigns a unit complex number to each orientation of an edge, and its inverse is assigned to the opposite orientation. The associated adjacency…

Combinatorics · Mathematics 2020-05-19 Aniruddha Samanta , M. Rajesh Kannan

The main aim of this study is to characterize new classes of multicone graphs which are determined by their signless Laplacian spectra, their Laplacian spectra and their adjacency spectra. A multicone graph is defined to be the join of a…

Combinatorics · Mathematics 2018-03-02 Ali Zeydi Abdian

Let $G$ be a connected graph on $n$ vertices and $D(G)$ its distance matrix. The formula for computing the determinant of this matrix in terms of the number of vertices is known when the graph is either a tree or {a} unicyclic graph. In…

A map graph is a graph admitting a representation in which vertices are nations on a spherical map and edges are shared curve segments or points between nations. We present an explicit fixed-parameter tractable algorithm for recognizing map…

Data Structures and Algorithms · Computer Science 2022-07-01 Patrizio Angelini , Michael A. Bekos , Giordano Da Lozzo , Martin Gronemann , Fabrizio Montecchiani , Alessandra Tappini

We consider quantum walks on a finite graphs to which infinite tails are attached. We explore how the propagating and bound states depend on the structure of the finite graph. The S-matrix for such graphs is defined. Its unitarity is proved…

Quantum Physics · Physics 2010-02-11 Martin Varbanov , Todd A. Brun

Two graphs are co-spectral if their respective adjacency matrices have the same multi-set of eigenvalues. A graph is said to be determined by its spectrum if all graphs that are co-spectral with it are isomorphic to it. We consider these…

Logic in Computer Science · Computer Science 2016-09-15 Anuj Dawar , Simone Severini , Octavio Zapata

Let $P$ be a set of $n$ points in the plane where each point $p$ of $P$ is associated with a radius $r_p>0$.The transmission graph $G=(P,E)$ of $P$ is defined as the directed graph such that $E$ contains an edge from $p$ to $q$ if and only…

Computational Geometry · Computer Science 2021-06-10 Shinwoo An , Eunjin Oh

In finite group theory, studying the prime graph of a group has been an important topic for almost the past half-century. Recently, prime graphs of solvable groups have been characterized in graph theoretical terms only. This now allows the…

Combinatorics · Mathematics 2020-11-19 Chris Florez , Jonathan Higgins , Kyle Huang , Thomas Michael Keller , Dawei Shen

Treewidth is an important and well-known graph parameter that measures the complexity of a graph. The Kneser graph Kneser(n,k) is the graph with vertex set $\binom{[n]}{k}$, such that two vertices are adjacent if they are disjoint. We…

Combinatorics · Mathematics 2015-06-08 Daniel J. Harvey , David R. Wood

It is well known that, in general, part of the spectrum of a graph can be obtained from the adjacency matrix of its quotient graph given by a regular partition. In this paper, we propose a method to obtain all the spectrum, and also the…

Combinatorics · Mathematics 2019-01-24 C. Dalfó , M. A. Fiol

Properties of graphs that can be characterized by the spectrum of the adjacency matrix of the graph have been studied systematically recently. Motivated by the complexity of these properties, we show that there are such properties for which…

Combinatorics · Mathematics 2020-01-28 Omid Etesami , Willem H. Haemers

We give the characteristic polynomial of the distance or adjacency matrix of the strong power graph of a finite group, and compute its distance and adjacency spectrum.

Combinatorics · Mathematics 2015-06-26 Xuanlong Ma

Let P be a finite set of points in general position in the plane. The structure of the complete graph K(P) as a geometric graph includes, for any pair [a,b],[c,d] of vertex-disjoint edges, the information whether they cross or not. The…

Combinatorics · Mathematics 2014-12-30 Chaya Keller , Micha A. Perles