Characterization on graphs which achieve a Das’ upper bound for Laplacian spectral radius Original Research Article

Let G = (V, E) be a graph on vertex set V = {v1,v2, … ,vn}. For any vertex vi, we denote by N(vi) the set of the vertices adjacent to vi in G. Das got the following upper bound for Laplacian spectral radius:λ1(G)less-than-or-equals, slantmax{N(vi)union or logical sumN(vj):1less-than-or-equals, slanti