Distance spectral radius and perfect matchings in graphs with given fractional property

Abstract

A matching in a graph $G$ is a set of independent edges in $G$. A perfect matching in a graph $G$ is a matching which saturates all the vertices of $G$. A fractional perfect matching in a graph $G$ is a function $h:E(G)\to [0,1]$ such that $\sum _{e\in E_G(v)}h(e)=1$ for every $v\in V(G)$, where $E_G(v)$ is the set of edges incident to $v$ in $G$. Clearly, the existence of a fractional perfect matching in a graph is a necessary condition for the graph to possess a perfect matching. Let $G$ be a $k$-connected graph of even order $n$ with a fractional perfect matching, where $k$ is a positive integer. We denote by $\mu (G)$ the distance spectral radius of $G$. In this paper, we prove that if $n\ge 8k+6$ and $\mu (G)\le \mu (K_k\vee (k{K}_1\cup K_3\cup K_{n-2k-3}))$, then $G$ contains a perfect matching unless $G=K_k\vee (k{K}_1\cup K_3\cup K_{n-2k-3})$.

9 pages