Corrigendum to the equivalent statement of the Laplacian Spread Conjecture

Abstract

For a graph $G,$ let $α(G)$ denote its second smallest Laplacian eigenvalue. The Laplacian Spread Conjecture states that $α(G)+α(\overline{G}) \geq 1,$ where $\overline{G}$ is the complement of $G.$ In this paper, we have corrected two conclusions: First, the necessary and sufficient condition for $α(G) + α(\overline{G}) \geq 1$ is $\parallel \bigtriangledown_{x} - \bigtriangledown_{y} \parallel^{2} \geq 1$ rather than $\parallel \bigtriangledown_{x} - \bigtriangledown_{y} \parallel^{2} \geq 2$ which has been proved in \cite{BS} as demonstrated in our study. Second, we show that the Laplacian spread of balanced digraph $Γ$ satisfies $LS(Γ) \leq n - \frac{1}{2}$ but not $LS(Γ) \leq n - 1$ in \cite{BCEHK}, since inequality $\parallel \bigtriangledown_{x} - \bigtriangledown_{y} \parallel^{2} \geq 2$ does not hold.