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Nuclear Theory·nucl-th

Friday·July 10, 2015

6 papers—3 primary·3 cross-listed

All6Primary3Cross-lists3
  1. 01

    General transformation of alpha cluster model wave function to jj-coupling shell model in various 4N nuclei

    N. Itagaki · H. Matsuno · T. Suhara

    The antisymmetrized quasi-cluster model (AQCM) is a method to describe a transition from the alpha-cluster wave function to the jj-coupling shell model wave function. In this model, the cluster-shell transition is characterized by only two parameters; R representing the distance between alpha clusters and Lambda describing the breaking of alpha clusters, and the contribution of the spin-orbit interaction, very important in the jj-coupling shell model, can be taken into account starting with the alpha cluster model wave function. In this article we show the generality of AQCM by extending the application to heavier region; various 4N nuclei from 4He to 52Fe. We show and compare the energy curves for the alpha+40Ca cluster configuration calculated with and without alpha breaking effect in 44Ti.

    nucl-thnucl-exPTEP(2016)·21 citations
  2. 02

    The BCS pairing gap in the on-shell limit of the Similarity Renormalization Group

    E. Ruiz Arriola · S. Szpigel · V.S. Timoteo

    The pairing gap plays a fundamental role in the nuclear many-body problem and many large scale and accurate mass formula fits suggest the smooth nuclear mass dependence in the liquid drop model which lacks a theoretical motivation. Within the BCS theory we analyze the impact of phase equivalent interactions on the pairing gap for a translational invariant many-fermion system such as nuclear and neutron matter. To that end we use explicitly the Similarity Renormalization Group (SRG) transformations. We show that in the on-shell and continuum limits the pairing gap vanishes. For finite size systems the pairing gap can be computed directly from the scattering phase-shifts by the formula where is the Fermi momentum and the level spacing at the Fermi energy which for the harmonic oscillator shell model becomes , so that The comparison with double differences from binding energies of stable nuclei is satisfactory and the discrepancy with the large scale analysis may be attributed to the lack of three-body forces. Nevertheless, the on-shell two-body interaction provides a basis for the dependency and accounts for 75\% of the coefficient .

    nucl-th2 citations
  3. 03

    Beyond the mean field in the particle-vibration coupling scheme

    M. Baldo (1) · P.F. Bortignon (2,3) · G. Colo' (2,3) · D. Rizzo (2) · L. Sciacchitano (2) ((1) INFN, Sezione di Catania, via S. Sofia 64, I-95123, Catania, Italy, (2) Dipartimento di Fisica, Universita' degli Studi di Milano, via Celoria 16, I-20133 Milano, Italy, (3) INFN, sezione di Milano, via Celoria 16, via Celoria 16, I-20133 Milano, Italy)

    The Energy Density Functional theory is one of the most used methods developed in nuclear structure. It is based on the assumption that the energy of the ground state is a functional only of the density profile. The method is extremely successful within the effective force approach, noticeably the Skyrme or Gogny forces, in reproducing the nuclear binding energies and other bulk properties along the whole mass table. Although the Density Functional is in this case represented formally as the Hartree-Fock mean field of an effective force, the corresponding single-particle states in general do not reproduce the phenomenology particularly well. To overcome this difficulty, a strategy has been developed where the effective force is adjusted to reproduce directly the single particle energies, trying to keep the ground state energy sufficiently well reproduced. An alternative route, that has been developed along several years, for solving this problem is to introduce the mean field fluctuations, as represented by the collective vibrations of the nuclear system, and their influence on the single particle dynamics and structure. This is the basis of the particle-vibration coupling model. In this paper we present a formal theory of the particle-vibration coupling model based on the Green' s function method. The theory extends to realistic effective forces the macroscopic particle-vibration coupling models and the (microscopic) Nuclear Field Theory. It is formalized within the functional derivative approach to many-body theory. An expansion in diagrams is devised for the single particle self-energy and the phonon propagator. Critical aspects of the particle-vibration coupling model are analysed in general. Applications at the lowest order of the expansion are presented and discussed.

    nucl-thJ.Phys.G(2015)·25 citations

Affiliations

first authorsco-authorsvia INSPIRE