132 research outputs found
Generalized Richardson-Gaudin Nuclear Models
The exact solvability of several nuclear models with non-degenerate
single-particle energies is outlined and leads to a generalization of
integrable Richardson-Gaudin models, like the -based fermion pairing, to
any simple Lie algebra. As an example, the model of T=1
pairing is discussed and illustrated for the case of Ge with
non-degenerate single-particle energies
Criticality in the configuration-mixed interacting boson model : (1) mixing
The case of U(5)-- mixing in the
configuration-mixed Interacting Boson Model is studied in its mean-field
approximation. Phase diagrams with analytical and numerical solutions are
constructed and discussed. Indications for first-order and second-order shape
phase transitions can be obtained from binding energies and from critical
exponents, respectively
Effective three-body interactions in nuclei
It is shown that the three-body forces in the shell, for which
recently evidence was found on the basis of spectroscopic properties of the Ca
isotopes and isotones, can be most naturally explained as an effective
interaction due to excluded higher-lying shells, in particular the
orbit.}Comment: 5 pages, 1 tables, accepted for publication in Europhysics Letter
Excitation of multiple giant dipole resonances: from spherical to deformed nuclei
The effect of deformation on the excitation of multiple giant dipole resonances is studied. Analytical expressions are derived in the framework of the interacting boson model for the energies and E1 properties of giant dipole resonances in spherical and deformed nuclei, and a numerical treatment of transitional nuclei is proposed. Coulomb-excitation cross sections are calculated in U and in the samarium isotopes
Garvey-Kelson relations and the new nuclear mass tables
Accepted for publication in Physical Review CWe discuss the Garvey-Kelson mass relations in an extended formalism and show how they can be used to test and improve the consistency of the most commonly used mass formulae, in order to achieve more accurate predictions
O(12) limit and complete classification of symmetry schemes in proton-neutron interacting boson model
It is shown that the proton-neutron interacting boson model (pnIBM) admits
new symmetry limits with O(12) algebra which break F-spin but preserves the
quantum number M_F. The generators of O(12) are derived and the quantum number
`v' of O(12) for a given boson number N is determined by identifying the
corresponding quasi-spin algebra. The O(12) algebra generates two symmetry
schemes and for both of them, complete classification of the basis states and
typical spectra are given. With the O(12) algebra identified, complete
classification of pnIBM symmetry limits with good M_F is established.Comment: 22 pages, 1 figur
Exact Solution of the Isovector Proton Neutron Pairing Hamiltonian
The complete exact solution of the T=1 neutron-proton pairing Hamiltonian is
presented in the context of the SO(5) Richardson-Gaudin model with
non-degenerate single-particle levels and including isospin-symmetry breaking
terms. The power of the method is illustrated with a numerical calculation for
Ge for a model space which is out of reach of modern
shell-model codes.Comment: To be published by Physical Review Letter
SU(3) realization of the rigid asymmetric rotor within the IBM
It is shown that the spectrum of the asymmetric rotor can be realized quantum
mechanically in terms of a system of interacting bosons. This is achieved in
the SU(3) limit of the interacting boson model by considering higher-order
interactions between the bosons. The spectrum corresponds to that of a rigid
asymmetric rotor in the limit of infinite boson number.Comment: 9 pages, 2 figures, LaTeX, epsfi
Boson-conserving one-nucleon transfer operator in the interacting boson model
The boson-conserving one-nucleon transfer operator in the interacting boson
model (IBA) is reanalyzed. Extra terms are added to the usual form used for
that operator. These new terms change generalized seniority by one unit, as the
ones considered up to now. The results obtained using the new form for the
transfer operator are compared with those obtained with the traditional form in
a simple case involving the pseudo-spin Bose-Fermi symmetry in its limit. Sizeable differences are
found. These results are of relevance in the study of transfer reactions to
check nuclear supersymmetry and in the description of (\beta)-decay within IBA.Comment: 13 pages, 1 table, 0 figures. To be published in Phys. Rev.
Nuclear masses and the number of valence nucleons
An improved version of the liquid drop model is presented. The addition of two terms, linear and quadratic in the total number of valence nucleons (particles or holes), improves the description of atomic masses, which can be fitted with an r.m.s. error of 1.2 MeV. Predictions are analysed an compared with those of established models. (c) 2007 Elsevier B.V. All rights reserved
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