RENORMALIZATION EFFECTS IN NUCLEI

Renormalization effects in nuclei, namely the calculation of the field theoretical processes which dress single-particle and collective degrees of freedom, lead to observable quantal states which constitute the main manifestation of the nuclear structure to external fields, among them inelastic and one- and two- particle transfer reactions, aside from decay processes. They result from the (nuclear) Field Theory (NFT) orthogonalization of the associated product basis states, and are thus intimately connected not only with a static, but also with a dynamic requirement of selfconsistency between mean field and density, allowing also for scattering processes (vertices). Such requirements are fulfilled through the diagonalization of the particle-vibration coupling Hamiltonian, properly supplemented by four point vertices, leading, among other things, to a single, unified source of ground state correlations (quantal zero point fluctuations). Through them, single-particle and collective degrees of freedom melt together into the physical states which display both features, emphasizing their common, complementary origin, closely related to the fact that nuclei respond elastically to rapid solicitations (shell model) and plastically over longer periods of time (liquid drop). It is found that renormalization effects are important in the description of both superfluid and normal nuclei. In particular, they contribute to 50% of the value of the pairing gap of 120Sn, and reduce by 40% the single-particle content of specific valence states of the exotic, closed shell nucleus 132Sn.