NEW RESULTS IN THE STUDY OF SUPERFLUID NUCLEI: MANY-BODY EFFECTS, SPECTROSCOPIC FACTORS

A quantitative calculation of the state-dependent pairing gap requires to go beyond the quasiparticle approximation, treating in detail the breaking of the single-particle strength (self-energy processes), and the induced interaction arising from the exchange of (QRPA) collective vibrations between pairs of nucleons, not to mention the vertex-corrections. Different Skyrme forces have been used for the HF basis to obtain different level densities at the Fermi energy, and special attention has been paid to the calculation of spectroscopic factors with the comparison with the (rather old) existing data. The agreement is encouraging, but the need of new data will be discussed.

Mention will be done of two other important works, discussing the relation of the typical induced-interaction matrix elements with those of the Gogny force and of the v_low-k nucleon-nucleon potential, and pointing-out also in finite nuclei the (relatively small) screening effect of the exchange of spin modes in the induced interaction.