设G是阶为n边数为m的简单图,λ1,λ2,…,λn是G的邻接矩阵的特征值,u1,u2,…,un是G的拉普拉斯矩阵的特征值.图G的能量定义为E(G)=∑i=1^n |λi|,拉普拉斯能量LE(G)=∑i=1^n |ui-2m/n|. 利用代数和图论的方法,得到了k-正则图的最大和最小能量,以及最大、最小拉普拉斯能量,并刻划了能量取到最值时对应的图的结构.
Let G be a graph with n vertices and m edges. Let λ1 ,λ2 ,…,λn be the eigenvalues of the adjacency matrix of G,and let u1,u2, …,un be the Laplacian matrix of G. The energy of G is defined as E (G)=∑i=1^n |λi| , the Laplacian energy LE (G) =∑i=1^n |ui-2m/n|. In this paper, by algebra and graph methods, we obtain the maximum and minimum energy and Laplacian energy of k-regular graph G of order n when it form a strongly regular graph, and character the corresponding graph respectively.