186 research outputs found
Neutrinoless Double-Beta Decay and Realistic Shell Model
No full textWe report on the calculation of the neutrinoless double-ß decay nuclear matrix element for 76Ge within the framework of the realistic shell model. The effective shell-model Hamiltonian and the two-body transition operator describing the decay are derived by way of many-body perturbation theory. Particular attention is focused on the role played by the so-called Pauli blocking effect in the derivation of the effective operator
Double-step truncation procedure for large-scale shell-model calculations
No full textWe present a procedure that is helpful to reduce the computational
complexity of large-scale shell-model calculations, by preserving as
much as possible the role of the rejected degrees of freedom in an
effective approach. Our truncation is driven first by the analysis of
the effective single-particle energies of the original large-scale
shell-model Hamiltonian, in order to locate the relevant degrees of
freedom to describe a class of isotopes or isotones, namely the
single-particle orbitals that will constitute a new truncated model
space. The second step is to perform a unitary transformation of the
original Hamiltonian from its model space into the truncated one. This
transformation generates a new shell-model Hamiltonian, defined in a
smaller model space, that retains effectively the role of the excluded
single-particle orbitals. As an application of this procedure, we have
chosen a realistic shell-model Hamiltonian defined in a large model
space, set up by seven proton and five neutron single-particle orbitals
outside Sr-88. We study the dependence of shell-model results upon
different truncations of the original model space for the Zr, Mo, Ru,
Pd, Cd, and Sn isotopic chains, showing the reliability of this
truncation procedure
Role of Three-Nucleon Forces in Neutron-Rich Nuclei Beyond 132Sn
No full textThe role of three-nucleon forces (3NF) in the description of nuclear structure properties is nowadays a main topic in the field of microscopic many-nucleon calculations. We investigate the relative weight between effective two- and three-nucleon forces in neutron-rich nuclei beyond the doubly-closed 132Sn core within the realistic shell-model framework, studying the evolution of the spectroscopic properties of N = 82 isotones and heavy tin isotopes. This problem is tackled indirectly without explicitly taking into account effective 3NF through the comparison of the results of shell-model calculations obtained from realistic on-shell-equivalent low-momentum potentials
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