摘要：The Kirchhoff index of is the sum of resistance distances between all pairs of vertices of in electrical networks. is the Laplacian-Energy-Like Invariant of in chemistry. In this paper, we define two classes of join graphs: the subdivision-vertex-vertex join and the subdivision-edge-edge join . We determine the generalized characteristic polynomial of them. We deduce the adjacency (Laplacian and signless Laplacian, resp.) characteristic polynomials of and when is -regular graph and is -regular graph. As applications, the Laplacian spectra enable us to get the formulas of the number of spanning trees, Kirchhoff index, and of and in terms of the Laplacian spectra of and .
