Distance signless Laplacian spectral radius and tough graphs involving minimun degree (2504.07501v2)

Abstract: Let $G=(V(G),E(G))$ be a simple graph, where $V(G)$ and $E(G)$ are the vertex set and the edge set of $G$, respectively. The number of components of $G$ is denoted by $c(G)$. Let $t$ be a positive real number, and a connected graph $G$ is $t$-tough if $t c(G-S)\leq|S|$ for every vertex cut $S$ of $V(G)$. The toughness of graph $G$, denoted by $\tau(G)$, is the largest value of $t$ for which $G$ is $t$-tough. Recently, Fan, Lin and Lu [European J. Combin. 110(2023), 103701] presented sufficient conditions based on the spectral radius for graphs to be 1-tough with minimum degree $\delta(G)$ and graphs to be $t$-tough with $t\geq 1$ being an integer, respectively. In this paper, we establish sufficient conditions in terms of the distance signless Laplacian spectral radius for graphs to be 1-tough with minimum degree $\delta(G)$ and graphs to be $t$-tough, where $\frac{1}{t}$ is a positive integer. Moreover, we consider the relationship between the distance signless Laplacian spectral radius and $t$-tough graphs in terms of the order $n$.