Structure of exotic nuclei around double shell closures

In this paper, we first give a brief review of the theoretical framework for microscopic shell-model calculations starting from the free nucleon-nucleon potential. In this context, we discuss the use of the low-momentum nucleon-nucleon interaction V-low-k in the derivation of the shell-model effective interaction and emphasize its practical value as an alternative to the Brueckner G-matrix method. Then, we present some results of our current study of exotic nuclei around doubly magic 132Sn, which have been obtained starting from the CD-Bonn potential renormalized by use of the V-low-k approach. Attention is focused on the nuclei 134Te, 134Sn, and 136Te, in particular on the latter which is a direct source of information on the proton-neutron effective interaction in the 132Sn region. Comparison shows that our results are in very good agreement with the available experimental data.Comment: 8 pages, 3 figures, to be published in Prog. Part. Nucl. Phy

Realistic shell-model calculations for neutron-rich calcium isotopes

We study the neutron-rich calcium isotopes performing shell-model calculations with a realistic effective interaction. This is derived from the CD-Bonn nucleon-nucleon potential renormalized by way of the V-low-k approach, considering 48Ca as an inert core and including the neutron 0g9/2 orbital. We compare our results with experiment and with the results of a previous study where 40Ca was assumed as a closed core and the standard 1p0f model space was employed. The calculated spectroscopic properties are in both cases in very good agreement with the available experimental data and enable a discussion on the role of the g9/2 single-particle state in the heavy-mass Ca isotopes.Comment: 7 pages, 1 figure, 4 tables, talk presented at 10th International Spring Seminar on Nuclear Physics "New Quests in Nuclear Structure", Vietri sul Mare, may 21-25, 2010. To be published on Journal of Physics Conference Serie

Self-Consistent Nuclear Shell-Model Calculation Starting from a Realistic NN Potential

First self-consistent realistic shell-model calculation for the light p-shell nuclei is performed, starting from the high-precision nucleon-nucleon (NN) CD-Bonn potential. This realistic potential is renormalized deriving a low-momentum NN potential V-low-k that preserves exactly the two-nucleon low-energy physics. This V-low-k is suitable to derive a self-consistent Hartree-Fock basis that is employed to derive both effective single-particle energies and residual two-body matrix elements for the shell-model hamiltonian. Results obtained show the reliability of such a fundamental microscopic approach.Comment: 4 pages, 1 figure, 8 tables, to be published on Physics Letters

Realistic Shell-Model Calculations for Nuclei in the Region of Shell Closures off Stability

We have performed realistic shell-model calculations for nuclei around doubly magic 100Sn and 132Sn using an effective interaction derived from the Bonn A nucleon-nucleon potential. The results are in remarkably good agreement with the experimental data showing the ability of our effective interaction to provide an accurate description of nuclear structure properties.Comment: 6 pages, 6 figures, Proceedings of the SNEC98 Conference, to be published on Nuovo Cimento

Observer design for piecewise smooth and switched systems via contraction theory

The aim of this paper is to present the application of an approach to study contraction theory recently developed for piecewise smooth and switched systems. The approach that can be used to analyze incremental stability properties of so-called Filippov systems (or variable structure systems) is based on the use of regularization, a procedure to make the vector field of interest differentiable before analyzing its properties. We show that by using this extension of contraction theory to nondifferentiable vector fields, it is possible to design observers for a large class of piecewise smooth systems using not only Euclidean norms, as also done in previous literature, but also non-Euclidean norms. This allows greater flexibility in the design and encompasses the case of both piecewise-linear and piecewise-smooth (nonlinear) systems. The theoretical methodology is illustrated via a set of representative examples.Comment: Preprint accepted to IFAC World Congress 201

g9/2 nuclei and neutron-proton interaction

We have performed shell-model calculations for nuclei below 100Sn, focusing attention on the two N=Z nuclei 96Cd and 92Pd, the latter having been recently the subject of great experimental and theoretical interest. We have considered nuclei for which the 0g9/2 orbit plays a dominant role and employed a realistic low-momentum two-body effective interaction derived from the CD-Bonn nucleon-nucleon potential. This implies that no phenomenological input enters our effective Hamiltonian. The calculated results for 92Pd are in very good agreement with the available experimental data, which gives confidence in our predictions for 96Cd. An analysis of the wave functions of both 96Cd and 92Pd is performed to investigate the role of the isoscalar spin-aligned coupling.Comment: 7 pages, 6 figures, 4 tables, to be published in Physical Review

Proton-neutron multiplets in exotic 134Sb: testing the shell-model effective interaction

The experimental level structure of 134Sb is compared with the results of a shell-model calculation in which the two-body matrix elements of the effective interaction have been derived from the CD-Bonn nucleon-nucleon potential. The experimental data, including the very low-lying first-excited 1- state, are remarkably well reproduced by the theory. The results of this paper complement those of our previous studies on 135Sb and 134Sn, showing that our effective interaction is well suited to describe 132Sn neighbors beyond N=82. The various terms which contribute to the matrix elements of the proton-neutron effective interaction are examined and their relative importance is evidenced.Comment: 4 pages, 3 figures, published on Physical Review