Mathematical background
The Normalized Laplacian of the graph G is the matrix L(G) defined as:
L(G) (u, v) = - (du+ dv) -1/2 if u and v are adjacent
The Normalized Laplacian Spectrum is the set of eigenvalues of L(G), i.e., all values ? such that
L(G) × u = ? × u for some u ? Rn, u ? 0.
Multiplicity of eigenvalue a is the number of eigenvalues that are equal to a.