Toughness and distance spectral radius in graphs

School of Mathematics and Statistics, Lanzhou University, Lanzhou, Gansu, P.R. China

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Received: 6 October 2025
Accepted: 30 June 2026

Abstract

Let G be a connected graph with vertex set V(G). A variation τ(G) of toughness of G, proposed by Enomoto in 1988, is defined as τ (G) = min S⊂V (G){|S|/c(G − S) − 1 : c(G − S) > 1}, where c(G−S) is the number of components of G−S for a subset S of V(G). For a positive real number τ, G is called τ-tough if τ(G)≥τ Chen et al. [Discrete Math. 347 (2024) 114191] gave sufficient spectral radius conditions for a graph G to be τ-tough, where the spectral radius is the maximum eigenvalue of the adjacent matrix of G and τ or 1/τ is a positive integer. Analogously, in this paper, we investigate the case of the distance spectral radius of G and present three tight distance spectral radius conditions, respectively, and analyze the extreme cases, which are similar to Chen et al.’s results.