Structure of the vacuum states in the presence of isovector and isoscalar pairing correlations - art. no. 024315

The long standing problem of proton-neutron pairing and, in particular, the Limitations imposed on the solutions by the available symmetries, is revis ited. We look for solutions with nonvanishing expectation values of the pro ton Delta(p), the neutron Delta(n), and the isoscalar Delta(o) gaps. For an equal number of protons and neutrons we find two solutions with Delta(p) = +/- Delta(n), respectively. The behavior and structure of these solutions differ for spin saturated (single l shell) and spin unsaturated systems (si ngle j shell). In the former case the BCS results are checked against an ex act calculation.