Ruifang Liu

activity

20152022

most citedOn the second largest distance eigenvalue of a graph

1 citations · 1 across the 6 of their papers we have counts for

collaborators

8 papers

math.CO2022

An improvement of sufficient condition for $k$ -leaf-connected graphs

Tingyan Ma, Guoyan Ao, Ruifang Liu +2

For integer $k \geq 2,$ a graph $G$ is called $k$ -leaf-connected if $∣ V (G) ∣ \geq k + 1$ and given any subset $S \subseteq V (G)$ with $∣ S ∣ = k,$ $G$ always has a spanning tree $T$ such that…

math.CO2022

Maxima of spectral radius of irregular graphs with given maximum degree

Jie Xue, Ruifang Liu

Let $λ^{*}$ be the maximum spectral radius of connected irregular graphs on $n$ vertices with maximum degree $Δ$ . Liu, Shen and Wang (2007) conjectured that $\lim_{n\rightarrow \in…

math.CO2020

A spectral extremal problem on graphs with given size and matching number

Mingqing Zhai, Jie Xue, Ruifang Liu

Brualdi and Hoffman (1985) proposed the problem of determining the maximal spectral radius of graphs with given size. In this paper, we consider the Brualdi-Hoffman type problem of…

math.CO2020

Fractional matching number and spectral radius of nonnegative matrix of graphs

Ruifang Liu, Hong-Jian Lai, Litao Guo +1

A fractional matching of a graph $G$ is a function $f : E (G) \to [0, 1]$ such that for any $v \in V (G)$ , $\sum_{e \in E_{G} (v)} f (e) \leq 1$ where $E_{G} (v) = {e \in E (G) : e$ is incident wit…

math.CO2019

Vertex-connectivity and $Q$ -index of graphs with fixed girth

Huicai Jia, Hong-Jian Lai, Ruifang Liu +1

Let $q (G)$ denote the $Q$ -index of a graph $G$ , which is the largest signless Laplacian eigenvalue of $G$ . We prove best possible upper bounds of $q (G)$ and best possible lower bou…

math.CO2018

A note on eigenvalues and Hamiltoinan properties of $k$ -connected graphs

Huicai Jia, Ruifang Liu, Hong-Jian Lai

Let $λ_{1} (G)$ and $μ_{1} (G)$ denote the spectral radius and the Laplacian spectral radius of a graph $G$ , respectively. Li in [Electronic J. Linear Algebra 34 (2018) 389-392] prov…

An improvement of sufficient condition for k-leaf-connected graphs