确定图的Signless Laplacian谱唯一性的第二个参数

The second parameter that determines uniqueness of Signless Laplacian spectrum of a graph

由图的边与多项式系数之间的关系和参数Π3(G),定义了另一个参数Π4(G),证明了它们的性质并刻画了所有Π4(G)=0,-1,-2,-3的连通图。

By using the coefficients of characteristic polynomials of the adjacency matrix A(G) and ∏3(G),we give a invariants ∏4(G) in this paper.Then some properties of the invariants are given.And we characterize all connected graphs with ∏4(G)=0,-1,-2,-3.