English

A{\alpha}-spectral radius and path-factor covered graphs

Combinatorics 2024-03-06 v1

Abstract

Let α[0,1)\alpha\in[0,1), and let GG be a connected graph of order nn with nf(α)n\geq f(\alpha), where f(α)=14f(\alpha)=14 for α[0,12]\alpha\in[0,\frac{1}{2}], f(α)=17f(\alpha)=17 for α(12,23]\alpha\in(\frac{1}{2},\frac{2}{3}], f(α)=20f(\alpha)=20 for α(23,34]\alpha\in(\frac{2}{3},\frac{3}{4}] and f(α)=51α+1f(\alpha)=\frac{5}{1-\alpha}+1 for α(34,1)\alpha\in(\frac{3}{4},1). A path factor is a spanning subgraph FF of GG such that every component of FF is a path with at least two vertices. Let k2k\geq2 be an integer. A PkP_{\geq k}-factor means a path-factor with each component being a path of order at least kk. A graph GG is called a PkP_{\geq k}-factor covered graph if GG has a PkP_{\geq k}-factor containing ee for any eE(G)e\in E(G). Let Aα(G)=αD(G)+(1α)A(G)A_{\alpha}(G)=\alpha D(G)+(1-\alpha)A(G), where D(G)D(G) denotes the diagonal matrix of vertex degrees of GG and A(G)A(G) denotes the adjacency matrix of GG. The largest eigenvalue of Aα(G)A_{\alpha}(G) is called the AαA_{\alpha}-spectral radius of GG, which is denoted by ρα(G)\rho_{\alpha}(G). In this paper, it is proved that GG is a P2P_{\geq2}-factor covered graph if ρα(G)>η(n)\rho_{\alpha}(G)>\eta(n), where η(n)\eta(n) is the largest root of x3((α+1)n+α4)x2+(αn2+(α22α1)n2α+1)xα2n2+(5α23α+2)n10α2+15α8=0x^{3}-((\alpha+1)n+\alpha-4)x^{2}+(\alpha n^{2}+(\alpha^{2}-2\alpha-1)n-2\alpha+1)x-\alpha^{2}n^{2}+(5\alpha^{2}-3\alpha+2)n-10\alpha^{2}+15\alpha-8=0. Furthermore, we provide a graph to show that the bound on AαA_{\alpha}-spectral radius is optimal.

Keywords

Cite

@article{arxiv.2403.02896,
  title  = {A{\alpha}-spectral radius and path-factor covered graphs},
  author = {Sizhong Zhou and Hongxia Liu and Qiuxiang Bian},
  journal= {arXiv preprint arXiv:2403.02896},
  year   = {2024}
}

Comments

18 pages

R2 v1 2026-06-28T15:09:41.288Z