Title
Graphs determined by their Aα-spectra.
Abstract
Let G be a graph with n vertices, and let A(G) and D(G) denote respectively the adjacency matrix and the degree matrix of G. Define Aα(G)=αD(G)+(1−α)A(G)for any real α∈[0,1]. The collection of eigenvalues of Aα(G) together with multiplicities are called the Aα-spectrum of G. A graph G is said to be determined by its Aα-spectrum if all graphs having the same Aα-spectrum as G are isomorphic to G. We first prove that some graphs are determined by their Aα-spectra for 0≤α<1, including the complete graph Kn, the union of cycles, the complement of the union of cycles, the union of copies of K2 and K1, the complement of the union of copies of K2 and K1, the path Pn, and the complement of Pn. Setting α=0 or 12, those graphs are determined by A- or Q-spectra. Secondly, when G is regular, we show that G is determined by its Aα-spectrum if and only if the join G∨Km (m≥2) is determined by its Aα-spectrum for 12<α<1. Furthermore, we also show that the join Km∨Pn (m,n≥2) is determined by its Aα-spectrum for 12<α<1. In the end, we pose some related open problems for future study.
Year
DOI
Venue
2019
10.1016/j.disc.2018.10.006
Discrete Mathematics
Keywords
Field
DocType
Aα-spectrum,Determined by the Aα-spectrum,Join
Adjacency matrix,Complete graph,Discrete mathematics,Combinatorics,Vertex (geometry),Multiplicity (mathematics),Spectral line,Isomorphism,Degree matrix,Eigenvalues and eigenvectors,Mathematics
Journal
Volume
Issue
ISSN
342
2
0012-365X
Citations 
PageRank 
References 
0
0.34
8
Authors
3
Name
Order
Citations
PageRank
Huiqiu Lin13411.56
Xiaogang Liu211.40
Jie Xue32512.59