图的谱理论是图论与组合矩阵论的一个重要研究领域。设图G是一个有n个顶点、m条边的简单图,Q(G)为图G的无符号拉普拉斯矩阵,树图是图论研究的一类重要的图,为了确定一类树的sL谱惟一性,利用图与同谱图之间的关系,运用删边缩边原理,探讨了两组顶点数目的树图。通过比较两组图中子树数目的大小逐项排除和删边删点的方法证明了一类树的SL谱惟一性。
The specrrum theory of graphs is an important area of investigation in the graph theory and Combinatorial matrix theory. Graph G is set as a simple graph with n top points and m edges, and Q(G) as its signless Laplacian (SL) matrix. In this paper, the relation between graphs and its cospectral graph is adopted to confirm the uniqueness of SL spectrum of the first-class tree. The tree graphs with two type numbers were investigated on the basis of comparison of two type graphs.