Symmetry under the discrete transformation CPT is a general theoretical condition holding for local relativistic field theories of point particles [1]-[7]. This symmetry has been investigated experimentally under different circumstances and to a high degree of precision [8]. The broad theoretical validity of CPT symmetry for particles and the availability of high-precision tests makes CPT viola...

For a large class of linear neutral type systems the problem of eigenvalues and eigenvectors assignment is investigated, i.e. finding the system which has the given spectrum and almost all, in some sense, eigenvectors.