A number projected model with generalized pairing interaction
  A mean-field model with a generalized pairing interaction that accounts for neutron-proton pairing is presented. Both the BCS as well as number-projected solutions of the model are presented. For the latter case the Lipkin-Nogami projection technique was extended to encompass the case of non-separable proton-neutron systems. The influence of the projection on various pairing phases is discussed. In particular, it is shown that number-projection allows for mixing of different pairing phases but, simultanously, acts destructively on the proton-neutron correlations. The basic implications of proton-neutron pairing correlations on nuclear masses are discussed. It is shown that these correlations may provide a natural microscopic explanation of the Wigner energy lacking in mean-field models. A possible phase transition from isovector to isoscalar pairing condensate at high angular momenta is also discussed. In particular predictions for the dynamical moments of inertia for the superdeformed band in $^{88}$Ru are given. 
W. Satula and R. Wyss