132 research outputs found

    Generalized Richardson-Gaudin Nuclear Models

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    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 su(2)su(2)-based fermion pairing, to any simple Lie algebra. As an example, the so(5)sp(4)so(5)\sim sp(4) model of T=1 pairing is discussed and illustrated for the case of 64^{64}Ge with non-degenerate single-particle energies

    Criticality in the configuration-mixed interacting boson model : (1) U(5)Q^(χ)Q^(χ)U(5)-\hat{Q}(\chi)\cdot\hat{Q}(\chi) mixing

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    The case of U(5)--Q^(χ)Q^(χ)\hat{Q}(\chi)\cdot\hat{Q}(\chi) 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

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    It is shown that the three-body forces in the 1f7/21f_{7/2} shell, for which recently evidence was found on the basis of spectroscopic properties of the Ca isotopes and N=28N=28 isotones, can be most naturally explained as an effective interaction due to excluded higher-lying shells, in particular the 2p3/22p_{3/2} orbit.}Comment: 5 pages, 1 tables, accepted for publication in Europhysics Letter

    Excitation of multiple giant dipole resonances: from spherical to deformed nuclei

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    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 238^{238}U and in the samarium isotopes

    Garvey-Kelson relations and the new nuclear mass tables

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    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

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    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

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    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 64^{64}Ge for a pf+g9/2pf+g_{9/2} 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

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    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

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    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 UB(6)UF(12)U^{B}(6) \otimes U^F(12) in its UBF(5)UF(2)U^{BF}(5) \otimes U^F(2) 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

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    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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