1,721,155 research outputs found
Perturbative Approach to Effective Shell-Model Hamiltonians and Operators
No full textThis article presents an overview of the derivation of effective shell-model Hamiltonian and decay operators within the framework of many-body perturbation theory, and discusses the results of selected shell-model studies based on these operators. More precisely, we give technical details that non-experts will need in order to derive shell-model Hamiltonians and operators starting from realistic nuclear potentials, and provide some guidance for shell-model calculations where the single-particle energies, two-body matrix elements of the residual interaction, effective charges, and decay matrix elements are all obtained without resorting to empirical adjustments. We report results of studies of double-β decay of heavy-mass nuclei where the shell-model ingredients are derived from theory, so as to assess the reliability of such an approach to shell-model investigations. Attention will be also focused on aspects relating to the behavior of the perturbative expansion, knowledge of which is needed for establishing limits and applying this approach to nuclear structure calculations
Gamow-Teller decays: Probing nuclear structure and weak interactions
Full text linkWe describe the Gamow-Teller decays for nuclear systems outside the 40 Ca and 56 Ni closed cores in the framework of the realistic shell model, starting from a nuclear Hamiltonian and electroweak currents as consistently obtained by means of chiral perturbation theory. The effective shell-model Hamiltonians and decay operators are derived using many-body perturbation theory, allowing the role of both electroweak currents and many-body correlations to be taken into account as the origin of the problem of the quenching of the axial coupling constant g A
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
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