Le Xu

collaborators

3 papers

math.CO2026

Extremal $Q$ -index problem in outerplanar graphs

Jin Cai, Leyou Xu, Bo Zhou

Outerplanar Turán problem has received considerable attention recently. We study the spectral version via $Q$ -index. We determine the unique graph that maximizes the $Q$ -index amon…

math.CO2025

Girth and Laplacian eigenvalue distribution

Leyou Xu, Bo Zhou

Let $G$ be a connected graph of order $n$ with girth $g$ . For $k = 1, \dots, min {g - 1, n - g}$ , let $n (G, k)$ be the number of Laplacian eigenvalues (counting multiplicities) of $G$ tha…

math.CO2025

Cycles and paths through specified vertices in graphs with a given clique number

Chengli Li, Leyou Xu

B. Bollobás and G. Brightwell and independently R. Shi proved the existence of a cycle through all vertices whose degrees at least $\frac{n}{2}$ in any $2$ -connected graph of order…

Extremal Q-index problem in outerplanar graphs

Girth and Laplacian eigenvalue distribution

Cycles and paths through specified vertices in graphs with a given clique number

Extremal $Q$ -index problem in outerplanar graphs