[en] The existence of collective vibrations in the spectrum implies that the description of the ground state in an independent particle model must be corrected. This is because of the zero point fluctuations induced by the collective vibrations, so that ground state correlations have to be included. These are taken into account via the diagrammatic expansion of the Nuclear Field Theory, giving place to a renormalization in the different properties of the ground state. As far as the density distribution is concerned, in a NFT consistent calculation, the largest contributions arise from diagrams that cannot be expressed in terms of backward going amplitudes of the phonon RPA wave function. For a given multipolarity the main correction comes from the low lying state. The giant resonance is of smaller relevance since it lies at larger energies in the response function. The octupole modes give the dominant contribution, and the effect in average becomes smaller as the multipolarity increases. These results agree quite well with those obtained taking into account the zero point fluctuations of the nuclear surface in the collective model with the Esbensen and Bertsch prescription, which the authors use to explain the anomalous behaviour of the mean square radii of the Calcium isotopes

[en] The charge and mass mean square radii of the Ca isotopes display an anomalous A-dependence. It is found that it can be correlated with the zero-point fluctuations associated with the low-lying collective states of the different isotopes. (orig.)

[en] The change of the nuclear density due to the zero point fluctuations associated with surface modes are calculated making use of field theoretical many-body techniques. For medium heavy nuclei the density renormalizations (vertex corrections) are much smaller than the potential renormalizations (self-energy contributions). The microscopic results agree well with the results of the collective model. Zero point fluctuations associated with pairing vibrations renormalize the properties of strongly rotating nuclei around the critical frequency at which the pairing phase transition takes place. Fluctuations of the pairing field play also an important role in the sub-barrier fusion cross section associated with the ⁵⁸Ni+⁶⁴Ni reaction. (orig.)

[en] We investigate the role the interweaving of surface vibrations and nucleon motion has on Cooper pair formation in spherical superfluid nuclei. This is done solving self-consistently the Dyson equation with the normal and anomalous density Green functions. Effective and realistic nucleon-nucleon interactions are used. It is found, that the pairing gap receives about equal contributions from the bare and from the induced interaction. It is furthermore found that the self-energy processes reduce the pairing gap by about 20%. The extreme cases of the ¹¹Li and ¹²Be nuclei are also discussed

[en] We perform a detailed calculation of the pairing properties of the inner crust of a neutron star. We focus on a specific density, and take into account the coexistence of a nuclear lattice with a superfluid gas of neutrons. The Hartree-Fock-Bogoliubov (HFB) equations are solved adding the matrix elements of the direct nucleon-nucleon interaction and those of the interaction induced by medium-polarization effects. The latter are obtained after a detailed calculation of the excited states of the system, within the random phase approximation. It is concluded that for the density considered, polarization processes reduce the pairing gap of about a factor of 2

[en] We investigate the role the interweaving of surface vibrations and nucleon motion has on Cooper pair formation in spherical superfluid nuclei. 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 and of the associated poles. This is done solving self-consistently the Dyson equation, including both a bare nucleon-nucleon interaction (which for simplicity we choose as a monopole-pairing force of constant matrix elements g) and an induced interaction arising from the exchange of vibrations (calculated microscopically in QRPA) between pairs of nucleons moving in time reversal states. Both the normal and anomalous density Green functions are included, thus treating self-energy and pairing processes on equal footing. We apply the formalism to the superfluid nucleus ¹²⁰Sn. Adjusting the value of g so as to reproduce, for levels close to the Fermi level, the empirical odd-even mass difference (Δ∼1.4 MeV), it is found that the pairing gap receives about equal contributions from the monopole-pairing force and from the induced interaction. This result is also reflected in the fact that if one were to reproduce the observed Δ allowing the nucleons to interact only through the bare monopole-pairing force, a value of g∼0.233 MeV (∼28/A MeV) is needed, 50% larger than the value g∼0.166 MeV (∼20/A MeV) needed in the full calculation. To keep in mind that the bare and the induced pairing contributions to Δ enter the corresponding equations in a very nonlinear fashion. It is furthermore found that self-energy processes reduce the contribution of the phonon induced interaction to the pairing gap by ∼20% as compared to the value obtained by only phonon exchange without taking into account the breaking of the single-particle strength

[en] An analysis is presented of the effect of the long-range residual interaction (LRRI) on the root mean square radius of charge (RMS radius) over a large range of nuclear masses. The implications of a consistent treatment of that effect on single-particle potentials and energies are also investigated. (author)

[en] Changes in the nuclear density arising from shape fluctuations are calculated in the case of the closed-shell nucleus /sup 40/Ca. The main contributions come from self-energy processes which renormalize the single-particle potential. Those due to ground-state correlations are much smaller. Processes involving the coupling to isoscalar vibrations are the most important, the role of isovector modes being small. Changes in the radius and in the diffusivity, of the order of 5% and 20%, respectively, are found

[en] For the first time, the Gogny force, a finite range interaction, is used to calculate self-consistently low-lying vibrational states and giant resonances in superfluid nuclei. The theoretical framework is based on the quasiparticle random phase approximation, starting from ground state wave functions obtained according to the Hartree-Fock-Bogoliubov theory. We study the isotopic chains of oxygen, nickel and tin isotopes, extending from the valley of stability towards the drip lines. It is found that the comparison with the experimental data is not very satisfactory. A critical analysis is attempted

[en] The absolute lifetimes of the four decay modes of /sup 234/U, namely α, Ne, and Mg decay, and spontaneous fission, are calculated within the superfluid tunneling model. It is found that a number of particles, of the order of twice the reduced mass of the two residual nuclei are moved around in the different processes. These particles belong to the condensed phase of the system and display, in their coherent motion, an inertia that is controlled by the pairing gap of the system, as well as by the number of nucleons participating. The model gives an overall account of the data, reproducing the observed lifetimes within two to three orders of magnitude