Gary Greaves, Haoran Zhu·2026-05-15·via math.CO updates on arXiv.org
We prove that if $Γ$ is a connected graph with minimum degree $δ$ and Laplacian eigenvalues $0=μ_1<μ_2\leqslant \cdots \leqslant μ_n$, then the toughness of $Γ$ is bounded below by $μ_2/(μ_n-δ)$.