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On eccentricity matrices of wheel graphs

  • I. Jeyaraman,
  • T. Divyadevi

摘要

The eccentricity matrix E(G) of a simple connected graph G is obtained from the distance matrix D(G) of G by retaining the largest distance in each row and column, and by defining the remaining entries to be zero. This paper focuses on the eccentricity matrix \(E(W_n)\) E ( W n ) of the wheel graph \(W_n\) W n with n vertices. By establishing a formula for the determinant of \(E(W_n)\) E ( W n ) , we show that \(E(W_n)\) E ( W n ) is invertible if and only if \(n \not \equiv 1\ (\textrm{mod}\ 3)\) n 1 ( mod 3 ) . We determine the inertia of \(E(W_n)\) E ( W n ) by obtaining the determinant and inertia of the eccentricity matrix of the fan graph. Further, we derive a formula for the inverse of \(E(W_n)\) E ( W n ) by finding a vector \(\textbf{w}\in \mathbb {R}^n\) w R n and an \(n \times n\) n × n symmetric Laplacian-like matrix \(\widetilde{L}\) L ~ of rank \(n-1\) n - 1 such that \(\begin{aligned} E(W_n)^{-1} = -\frac{1}{2}\widetilde{L} + \frac{6}{n-1}\textbf{w}\mathbf {w^{\prime }}. \end{aligned}\) E ( W n ) - 1 = - 1 2 L ~ + 6 n - 1 w w .