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

Abstract

Let $\alpha\in[0,1)$, and let $G$ be a connected graph of order $n$ with $n\geq f(\alpha)$, where $f(\alpha)=14$ for $\alpha\in[0,\frac{1}{2}]$, $f(\alpha)=17$ for $\alpha\in(\frac{1}{2},\frac{2}{3}]$, $f(\alpha)=20$ for $\alpha\in(\frac{2}{3},\frac{3}{4}]$ and $f(\alpha)=\frac{5}{1-\alpha}+1$ for $\alpha\in(\frac{3}{4},1)$. A path factor is a spanning subgraph $F$ of $G$ such that every component of $F$ is a path with at least two vertices. Let $k\geq2$ be an integer. A $P_{\geq k}$-factor means a path-factor with each component being a path of order at least $k$. A graph $G$ is called a $P_{\geq k}$-factor covered graph if $G$ has a $P_{\geq k}$-factor containing $e$ for any $e\in E(G)$. Let $A_{\alpha}(G)=\alpha D(G)+(1-\alpha)A(G)$, where $D(G)$ denotes the diagonal matrix of vertex degrees of $G$ and $A(G)$ denotes the adjacency matrix of $G$. The largest eigenvalue of $A_{\alpha}(G)$ is called the $A_{\alpha}$-spectral radius of $G$, which is denoted by $\rho_{\alpha}(G)$. In this paper, it is proved that $G$ is a $P_{\geq2}$-factor covered graph if $\rho_{\alpha}(G)>\eta(n)$, where $\eta(n)$ is the largest root of $x^{3}-((\alpha+1)n+\alpha-4)x^{2}+(\alpha n^{2}+(\alpha^{2}-2\alpha-1)n-2\alpha+1)x-\alpha^{2}n^{2}+(5\alpha^{2}-3\alpha+2)n-10\alpha^{2}+15\alpha-8=0$. Furthermore, we provide a graph to show that the bound on $A_{\alpha}$-spectral radius is optimal.