At the end of the spectrum: Chromatic bounds for the largest eigenvalue of the normalized Laplacian

Fuente: arXiv
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Auteurs principaux: Beers, Lies, Mulas, Raffaella
Format: Preprint
Publié: 2024
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author Beers, Lies
Mulas, Raffaella
author_facet Beers, Lies
Mulas, Raffaella
contents For a graph with largest normalized Laplacian eigenvalue $λ_N$ and (vertex) coloring number $χ$, it is known that $λ_N\geq χ/(χ-1)$. Here we prove properties of graphs for which this bound is sharp, and we study the multiplicity of $χ/(χ-1)$. We then describe a family of graphs with largest eigenvalue $χ/(χ-1)$. We also study the spectrum of the $1$-sum of two graphs (also known as graph joining or coalescing), with a focus on the maximal eigenvalue. Finally, we give upper bounds on $λ_N$ in terms of $χ$.
format Preprint
id arxiv_https___arxiv_org_abs_2402_09160
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle At the end of the spectrum: Chromatic bounds for the largest eigenvalue of the normalized Laplacian
Beers, Lies
Mulas, Raffaella
Combinatorics
Spectral Theory
For a graph with largest normalized Laplacian eigenvalue $λ_N$ and (vertex) coloring number $χ$, it is known that $λ_N\geq χ/(χ-1)$. Here we prove properties of graphs for which this bound is sharp, and we study the multiplicity of $χ/(χ-1)$. We then describe a family of graphs with largest eigenvalue $χ/(χ-1)$. We also study the spectrum of the $1$-sum of two graphs (also known as graph joining or coalescing), with a focus on the maximal eigenvalue. Finally, we give upper bounds on $λ_N$ in terms of $χ$.
title At the end of the spectrum: Chromatic bounds for the largest eigenvalue of the normalized Laplacian
topic Combinatorics
Spectral Theory
url https://arxiv.org/abs/2402.09160