ABSTRACT
This chapter deals with the Schrödinger eigenproblem in global spectral analysis. One can solve two eigenvalue problems in succession, since diagonalization of S precedes that of U. Each of these two diagonalizations customarily leads to spurious eigenvalues. This problem could be considerably mitigated if an orthogonal basis set is used from the onset, which deals only with ordinary eigenvalue problems where the matrix S is not present at all. Such a basis has been thoroughly analysed using the Lanczos recursive algorithm of wave packet propagations.
