Spectra and Laplacian spectra of arbitrary powers of lexicographic products of graphs

Fuente: arXiv
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Autores principales: Abreu, Nair, Cardoso, Domingos M., Carvalho, Paula, Vinagre, Cybele T. M.
Formato: Preprint
Publicado: 2015
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author Abreu, Nair
Cardoso, Domingos M.
Carvalho, Paula
Vinagre, Cybele T. M.
author_facet Abreu, Nair
Cardoso, Domingos M.
Carvalho, Paula
Vinagre, Cybele T. M.
contents Consider two graphs $G$ and $H$. Let $H^k[G]$ be the lexicographic product of $H^k$ and $G$, where $H^k$ is the lexicographic product of the graph $H$ by itself $k$ times. In this paper, we determine the spectrum of $H^k[G]$ and $H^k$ when $G$ and $H$ are regular and the Laplacian spectrum of $H^k[G]$ and $H^k$ for $G$ and $H$ arbitrary. Particular emphasis is given to the least eigenvalue of the adjacency matrix in the case of lexicographic powers of regular graphs, and to the algebraic connectivity and the largest Laplacian eigenvalues in the case of lexicographic powers of arbitrary graphs. This approach allows the determination of the spectrum (in case of regular graphs) and Laplacian spectrum (for arbitrary graphs) of huge graphs. As an example, the spectrum of the lexicographic power of the Petersen graph with the googol number (that is, $10^{100}$) of vertices is determined. The paper finish with the extension of some well known spectral and combinatorial invariant properties of graphs to its lexicographic powers.
format Preprint
id arxiv_https___arxiv_org_abs_1511_02391
institution arXiv
publishDate 2015
record_format arxiv
spellingShingle Spectra and Laplacian spectra of arbitrary powers of lexicographic products of graphs
Abreu, Nair
Cardoso, Domingos M.
Carvalho, Paula
Vinagre, Cybele T. M.
Combinatorics
05C50, 05C76, 15A18
Consider two graphs $G$ and $H$. Let $H^k[G]$ be the lexicographic product of $H^k$ and $G$, where $H^k$ is the lexicographic product of the graph $H$ by itself $k$ times. In this paper, we determine the spectrum of $H^k[G]$ and $H^k$ when $G$ and $H$ are regular and the Laplacian spectrum of $H^k[G]$ and $H^k$ for $G$ and $H$ arbitrary. Particular emphasis is given to the least eigenvalue of the adjacency matrix in the case of lexicographic powers of regular graphs, and to the algebraic connectivity and the largest Laplacian eigenvalues in the case of lexicographic powers of arbitrary graphs. This approach allows the determination of the spectrum (in case of regular graphs) and Laplacian spectrum (for arbitrary graphs) of huge graphs. As an example, the spectrum of the lexicographic power of the Petersen graph with the googol number (that is, $10^{100}$) of vertices is determined. The paper finish with the extension of some well known spectral and combinatorial invariant properties of graphs to its lexicographic powers.
title Spectra and Laplacian spectra of arbitrary powers of lexicographic products of graphs
topic Combinatorics
05C50, 05C76, 15A18
url https://arxiv.org/abs/1511.02391