Isoinvariant linearization and analog splitting

It is shown that the conventional linearization scheme, used to reduce the dimensionality of many-fermion–nucleon operators (e.g. in deriving RPA equations), is inadequate for the neutronrich nuclei, i.e., it is non-isoinvariant. A similar but isoinvariant scheme is introduced and applied successfully in obtaining the analog energy splitting of a single-proton state in a neutronrich nucleus.