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A consistent treatment of intrinsic and collective coordinates is applied to the calculation of matrix elements describing nuclear double beta decay transitions. The method, which was developed for the case of nuclear rotations, is adapted to include isospin and number of particles degrees of freedom. It is shown that the uncertainties found in most models, in dealing with these decay modes, are largely due to the mixing of physical and spurious effects in the treatment of isospin dependent interactions.

The hadronic decays of non-strange negative parity baryons are analyzed in the framework of the 1/Nc expansion. A complete basis of spin-flavor operators for the pseudoscalar meson S and D partial wave amplitudes is established to order 1/Nc and the unknown effective coefficients are determined by fitting to the empirically known widths. A set of relations between widths that result at the leading order, i.e. order Nc^0, is given and tested with the available data., Comment: 8 pages. Contribution to Large Nc QCD 2004 workshop, July 2004, ECT*, Trento, Italy

We study the parity violating hyperon non-leptonic weak decays in the three flavor Skyrme model. We follow the approach in which the symmetry breaking terms in the action are diagonalized exactly within the collective coordinate approximation. We show that although this method introduces some configuration mixing, the $\Delta I =1/2$ rule is numerically well satisfied. In addition, and in contrast to previous calculations, we show that not only the relative amplitudes are in good agreement with the empirical values but also their absolute values. The issue of whether the strong interaction enhancement factors should be included in soliton calculations is also addressed., Comment: 8 pages, LaTeX, no figures

A study is made of the electromagnetic decay of the 208Pb giant quadrupole resonance excited by inelastic scattering of 17O at 380 MeV. Due to the instability of the giant quadrupole resonance with respect to compound-nucleus formation and to neutron emission, the time over which the radiation is produced is not much greater than the time in which the direct reaction occurs. Angular distributions of the γ-rays produced in transitions to several low-lying states of the residual nucleus are calculated and their dependence on effects due to the proximity of the interacting nuclei is discussed.

The shape of the specific heat peak corresponding to finite and superconductive systems is studied for very simple models. It is shown that both types of peaks have a similar behavior.

We analyze experiments on the electromagnetic decay of the GQR from the point of view of the microscopic theory of the nuclear structure. The calculations are made systematically in the lowest contributing order of perturbation theory within the NFT formalism. Care is taken in order to prevent spurious mixing of the isoscalar and isovector parts of dipole operators. As in previous theoretical calculations, the results are consistent with the experimental limit of the ratio between the transition populating the 2.62 MeV 3 − state and the g.s. However they fail to reproduce the strong dipole transition to the 4.97 MeV 3 − state.

Previous NFT calculations of the four-particle spectrum reached different conclusions concerning the applicability of the lowest-order Rayleigh-Schroedinger perturbation expansion. In the present paper, we show that the inclusion of second-order diagrams and/or diagonalization procedures yields satisfactory results both for the energies and for the transfer matrix elements even for j-shells as small as the j = 7 2 and j = 11 2 shells.

International audience; Theoretical prediction of nuclear masses is analyzed as a pattern recognition problem on the N-Z plane. A global pattern is observed by plotting the differences between measured masses and Liquid Drop Model (LDM) predictions. After unfolding the data by removing the smooth LDM mass contributions, the remaining microscopic effects have proved difficult to model, although they display a striking pattern. These deviations carry information related to shell closures, nuclear deformation and the residual nuclear interactions. In the present work the more than 2000 known nuclear masses are studied as an array in the N-Z plane viewed through a mask, behind which the approximately 7000 unknown unstable nuclei that can exist between the proton and neutron drip lines are hidden. Employing a Fourier transform deconvolution method these masses can be predicted. Measured masses are reconstructed with and r.m.s. error of less than 200 keV. The existence of an island of stability around (Z\approx$ 116, N\approx 194) is strongly suggested. Other potential applications of the present approach are outlined.

International audience; Recent experimental data showing the interplay between fusion hindrance effects and the onset of the quasi-fission mechanism are presented. The aim of such investigations is understanding the role of entrance channel properties on the competing fusion-fission and quasi-fission processes, also in connection with the possible implications for superheavy element production. In this context, the role of mass asymmetry, nuclear deformation and shell effects is discussed.