Spectral extremal problems for $(a,b,k)$-critical and fractional $(a,b,k)$-critical graphs

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Autori principali: Xu, Zengzhao, Wang, Ligong, Xi, Weige
Natura: Preprint
Pubblicazione: 2025
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author Xu, Zengzhao
Wang, Ligong
Xi, Weige
author_facet Xu, Zengzhao
Wang, Ligong
Xi, Weige
contents A factor of a graph is essentially a specific type spanning subgraph. The study of characterizing the existence of $[a, b]$-factors based on eigenvalue conditions can be traced back to the work of Brouwer and Haemers (2005) on perfect matchings. With the advancement of graphs factor theory, the related spectral extremal problems, particularly the study of $[a,b]$-factors and fractional $[a,b]$-factors, have been widely studied by scholars. Our work is motivated by research related to the $[a,b]$-factors and fractional $[a,b]$-factors, and explores their generalizations: $(a,b,k)$-critical graphs and fractional $(a,b,k)$-critical graphs. A graph $G$ is called an $(a,b,k)$-critical (a fractional $(a,b,k)$-critical) graph if after deleting any $k$ vertices of $G$ the remaining graph of $G$ has an $[a,b]$-factor (a fractional $[a,b]$-factor). In this paper, we establish spectral radius conditions for a graph to be $(a,b,k)$-critical or fractional $(a,b,k)$-critical. When $k=0$, our results also resolve some open problems concerning $[a, b]$-factors and fractional $[a, b]$-factors.
format Preprint
id arxiv_https___arxiv_org_abs_2512_20971
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Spectral extremal problems for $(a,b,k)$-critical and fractional $(a,b,k)$-critical graphs
Xu, Zengzhao
Wang, Ligong
Xi, Weige
Combinatorics
A factor of a graph is essentially a specific type spanning subgraph. The study of characterizing the existence of $[a, b]$-factors based on eigenvalue conditions can be traced back to the work of Brouwer and Haemers (2005) on perfect matchings. With the advancement of graphs factor theory, the related spectral extremal problems, particularly the study of $[a,b]$-factors and fractional $[a,b]$-factors, have been widely studied by scholars. Our work is motivated by research related to the $[a,b]$-factors and fractional $[a,b]$-factors, and explores their generalizations: $(a,b,k)$-critical graphs and fractional $(a,b,k)$-critical graphs. A graph $G$ is called an $(a,b,k)$-critical (a fractional $(a,b,k)$-critical) graph if after deleting any $k$ vertices of $G$ the remaining graph of $G$ has an $[a,b]$-factor (a fractional $[a,b]$-factor). In this paper, we establish spectral radius conditions for a graph to be $(a,b,k)$-critical or fractional $(a,b,k)$-critical. When $k=0$, our results also resolve some open problems concerning $[a, b]$-factors and fractional $[a, b]$-factors.
title Spectral extremal problems for $(a,b,k)$-critical and fractional $(a,b,k)$-critical graphs
topic Combinatorics
url https://arxiv.org/abs/2512.20971