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The spectrum of Laplacian and signless Laplacian matrix for a graph product is obtained, where both underlying graphs are regular. As an application of this, we have been able to generate the Kirchhoff Index and Wiener Index and determine…

Combinatorics · Mathematics 2024-10-18 Bishal Sonar , Ravi Srivastava

This paper introduces the concept of $\mu$-signed and duplication signed graphs and shows that both are always structurally balanced. Using the duplication signed graph, we define the corona product of the duplication signed graph…

Combinatorics · Mathematics 2025-10-31 Bishal Sonar , Ravi Srivastava

We characterize when the spectral variation of the signed Laplacian matrices is integral after a new edge is added to a signed graph. As an application, for every fixed signed complete graph, we fully characterize the class of signed graphs…

Combinatorics · Mathematics 2024-01-08 Jungho Ahn , Cheolwon Heo , Sunyo Moon

A signed graph is a graph whose edges are labeled either positive or negative. Corresponding to the two signed distance matrices defined for signed graphs, we define two signed distance laplacian matrices. We characterize balance in signed…

Combinatorics · Mathematics 2020-10-12 Roshni T Roy , K A Germina , K Shahul Hameed , Thomas Zaslavsky

It is well known that a graph $G$ has a symmetric spectrum if and only if it is bipartite, a signed graph $\Gamma=(G,\sigma)$ has a symmetric spectrum if $G$ is bipartite. However, there exists a spectrally symmetric signed graph…

Combinatorics · Mathematics 2025-05-02 Deqiong Li , Qiongxiang Huang

We study the symmetry properties of the spectra of normalized Laplacians on signed graphs. We find a new machinery that generates symmetric spectra for signed graphs, which includes bipartiteness of unsigned graphs as a special case.…

Combinatorics · Mathematics 2016-02-16 Fatihcan M. Atay , Bobo Hua

Let $\Gamma=(G,\sigma)$ be a signed graph, where $\sigma$ is the sign function on the edges of $G$. In this paper, we use the operation of partial transpose to obtain non-isomorphic Laplacian cospectral signed graphs. We will introduce two…

Combinatorics · Mathematics 2022-05-19 Tahir Shamsher , S. Pirzada , Mushtaq A. Bhat

The spectral theory of the normalized Laplacian for chemical hypergraphs is further investigated. The signless normalized Laplacian is introduced and it is shown that its spectrum for classical hypergraphs coincides with the spectrum of the…

Combinatorics · Mathematics 2022-11-09 Eleonora Andreotti , Raffaella Mulas

We obtain new bounds for the Laplacian spectral radius of a signed graph. Most of these new bounds have a dependence on edge sign, unlike previously known bounds, which only depend on the underlying structure of the graph. We then use some…

Combinatorics · Mathematics 2011-03-25 Nathan Reff

We introduce the concept of a $k$-token signed graph and study some of its combinatorial and algebraic properties. We prove that two switching isomorphic signed graphs have switching isomorphic token graphs. Moreover, we show that the…

Combinatorics · Mathematics 2024-03-06 C. Dalfó , M. A. Fiol , E. Steffen

A signed graph is a graph in which each edge has a positive or negative sign. In this article, first we characterize the distance compatibility in the case of a connected signed graph and discussed the distance compatibility criterion for…

Combinatorics · Mathematics 2020-09-21 T. V. Shijin , P. Soorya , K. Shahul Hameed , K. A. Germina

The total graph is built by joining the graph to its line graph by means of the incidences. We introduce a similar construction for signed graphs. Under two similar definitions of the line signed graph, we define the corresponding total…

Combinatorics · Mathematics 2021-06-21 Francesco Belardo , Zoran Stanić , Thomas Zaslavsky

Signed graphs are graphs whose edges get a sign $+1$ or $-1$ (the signature). Signed graphs can be studied by means of graph matrices extended to signed graphs in a natural way. Recently, the spectra of signed graphs have attracted much…

Combinatorics · Mathematics 2019-07-11 Francesco Belardo , Sebastian M. Cioabă , Jack H. Koolen , Jianfeng Wang

In the past decades, graphs that are determined by their spectrum have received more attention, since they have been applied to several fields, such as randomized algorithms, combinatorial optimization problems and machine learning. An…

Combinatorics · Mathematics 2018-06-27 Ali Zeydi Abdian , Afshin Behmaram , Gholam Hossein Fath-Tabar

A signed graph is a graph whose edges are signed. In a vertex-signed graph the vertices are signed. The latter is called consistent if the product of signs in every circle is positive. The line graph of a signed graph is naturally…

Combinatorics · Mathematics 2021-06-21 Thomas Zaslavsky

In this article we examine the adjacency and Laplacian matrices and their eigenvalues and energies of the general product (non-complete extended $p$-sum, or NEPS) of signed graphs. We express the adjacency matrix of the product in terms of…

Combinatorics · Mathematics 2016-10-18 K. A. Germina , Shahul Hameed K , Thomas Zaslavsky

In this paper, we extend our earlier proposal of corona product of signed graphs into generalized corona product of signed graphs inspired by the generalized corona product of unsigned graphs. Then we study structural balance and spectral…

Combinatorics · Mathematics 2023-10-13 Amrik Singh , Ravi Srivastava , Bibhas Adhikari , Sandeep Kumar Yadav

We construct infinitely many signed graphs having symmetric spectrum, by using the NEPS and rooted product of signed graphs. We also present a method for constructing large cospectral signed graphs. Although the obtained family contains…

Combinatorics · Mathematics 2019-09-17 Farzaneh Ramezani

A signed graph is said to be sign-symmetric if it is switching isomorphic to its negation. Bipartite signed graphs are trivially sign-symmetric. We give new constructions of non-bipartite sign-symmetric signed graphs. Sign-symmetric signed…

Combinatorics · Mathematics 2020-03-24 Ebrahim Ghorbani , Willem H. Haemers , Hamid Reza Maimani , Leila Parsaei Majd

The nullity of a graph is the multiplicity of the eigenvalues zero in its spectrum. A signed graph is a graph with a sign attached to each of its edges. In this paper, we obtain the coefficient theorem of the characteristic polynomial of a…

Combinatorics · Mathematics 2016-11-25 Yu Liu , Lhua You
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