Deqiong Li

activity

20182023

collaborators

3 papers

math.CO2023

The signed graphs with symmetric spectra

Deqiong Li, Qiongxiang Huang

It is well known that a graph $G$ has a symmetric spectrum if and only if it is bipartite, a signed graph $Γ = (G, σ)$ has a symmetric spectrum if $G$ is bipartite. However, there exi…

math.CO2022

Extremed signed graphs for triangle

Dijian Wang, Yaoping Hou, Deqiong Li

In this paper, we study the Turán problem of signed graphs version. Suppose that $G ˙$ is a connected unbalanced signed graph of order $n$ with $e (G ˙)$ edges and $e^-(\dot…

math.CO2018

The graphs with all but two eigenvalues equal to $2$ or $- 1$

Jing Li, Deqiong Li, Yaoping Hou

In this paper, all graphs whose adjacency matrix has at most two eigenvalues (multiplicities included) different from $2$ and $- 1$ are determined. These graphs conclude a class of…

The signed graphs with symmetric spectra

Extremed signed graphs for triangle

The graphs with all but two eigenvalues equal to 2 or −1

The graphs with all but two eigenvalues equal to $2$ or $- 1$