Laplacian Spectra of Regular Graph Transformations

For any given graph G = (V,E) we define in a certain way a new graph G(x,y,z) with the vertex set V\cup E depending on parameters x,y,z from {0,1, +, -} and call graph G(x,y,z) the (x,y,z)-transformation of G. It turns out that if G is an r-regular graph, then the Laplacian polynomial of G(x,y,z) is a function of |V|, r, and the Laplacian spectrum of G. We give a complete description of this function.