Adjacency-diametrical matrix of a graph

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Main Authors: Amruthavarshini, S. P. Leka, Rajkumar, R.
Format: Preprint
Published: 2026
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author Amruthavarshini, S. P. Leka
Rajkumar, R.
author_facet Amruthavarshini, S. P. Leka
Rajkumar, R.
contents The adjacency-diametrical matrix (AD matrix) of a connected graph $G$ with diameter $d$, denoted by $AD(G)$, is the matrix indexed by the vertices of $G$ in which the $(i,j)$-entry of $AD(G)$ is $1$ if $d_G(v_i,v_j)=1$, is $d$ if $d_G(v_i,v_j)=d$, and $0$ otherwise, where $d_G(v_i,v_j)$ denotes the distance between the vertices $v_i$ and $v_j$ in $G$. We determine the spectrum of the AD matrix for paths, cycles, and double star graphs and obtain its determinant for a connected graph. We characterize a class of bipartite graphs using the coefficients of the characteristic polynomial and the eigenvalues of the AD matrix. We establish bounds relating the eigenvalues of the AD matrix to various graph invariants, and we determine the spectrum of the AD matrix for graphs formed by the join, lexicographic product, and Cartesian product operations under certain conditions on the constituent graphs.
format Preprint
id arxiv_https___arxiv_org_abs_2601_01193
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Adjacency-diametrical matrix of a graph
Amruthavarshini, S. P. Leka
Rajkumar, R.
Combinatorics
Spectral Theory
05C12, 05C50, 05C69, 05C15, 05C76
The adjacency-diametrical matrix (AD matrix) of a connected graph $G$ with diameter $d$, denoted by $AD(G)$, is the matrix indexed by the vertices of $G$ in which the $(i,j)$-entry of $AD(G)$ is $1$ if $d_G(v_i,v_j)=1$, is $d$ if $d_G(v_i,v_j)=d$, and $0$ otherwise, where $d_G(v_i,v_j)$ denotes the distance between the vertices $v_i$ and $v_j$ in $G$. We determine the spectrum of the AD matrix for paths, cycles, and double star graphs and obtain its determinant for a connected graph. We characterize a class of bipartite graphs using the coefficients of the characteristic polynomial and the eigenvalues of the AD matrix. We establish bounds relating the eigenvalues of the AD matrix to various graph invariants, and we determine the spectrum of the AD matrix for graphs formed by the join, lexicographic product, and Cartesian product operations under certain conditions on the constituent graphs.
title Adjacency-diametrical matrix of a graph
topic Combinatorics
Spectral Theory
05C12, 05C50, 05C69, 05C15, 05C76
url https://arxiv.org/abs/2601.01193