Nonregular graphs with a given maximum degree attaining maximum spectral radius

Fuente: arXiv
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Autori principali: Huang, Zejun, Liu, Jiahui, Yang, Chenxi
Natura: Preprint
Pubblicazione: 2024
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author Huang, Zejun
Liu, Jiahui
Yang, Chenxi
author_facet Huang, Zejun
Liu, Jiahui
Yang, Chenxi
contents Let $G$ be a connected nonregular graphs of order $n$ with maximum degree $Δ$ that attains the maximum spectral radius. Liu and Li (2008) proposed a conjecture stating that $G$ has a degree sequence $(Δ,\ldots,Δ,δ)$ with $δ<Δ$. For $Δ=3$ and $Δ=4$, Liu (2024) confirmed this conjecture by characterizing the structure of such graphs. Liu also proposed a modified version of the conjecture for fixed $Δ$ and sufficiently large $n$, stating that the above $δ=Δ-1$ if $Δ$ and $n$ are both odd, $δ=1$ if $Δ$ is odd and $n$ is even, and $δ=Δ-2$ if $Δ$ is even. For the cases where $Δ=n-2$ with $n\ge 5$, and $Δ=n-3$ with $n\ge 59$, we fully characterize the structure of $G$.
format Preprint
id arxiv_https___arxiv_org_abs_2411_17371
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Nonregular graphs with a given maximum degree attaining maximum spectral radius
Huang, Zejun
Liu, Jiahui
Yang, Chenxi
Combinatorics
Let $G$ be a connected nonregular graphs of order $n$ with maximum degree $Δ$ that attains the maximum spectral radius. Liu and Li (2008) proposed a conjecture stating that $G$ has a degree sequence $(Δ,\ldots,Δ,δ)$ with $δ<Δ$. For $Δ=3$ and $Δ=4$, Liu (2024) confirmed this conjecture by characterizing the structure of such graphs. Liu also proposed a modified version of the conjecture for fixed $Δ$ and sufficiently large $n$, stating that the above $δ=Δ-1$ if $Δ$ and $n$ are both odd, $δ=1$ if $Δ$ is odd and $n$ is even, and $δ=Δ-2$ if $Δ$ is even. For the cases where $Δ=n-2$ with $n\ge 5$, and $Δ=n-3$ with $n\ge 59$, we fully characterize the structure of $G$.
title Nonregular graphs with a given maximum degree attaining maximum spectral radius
topic Combinatorics
url https://arxiv.org/abs/2411.17371