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Nuclear Theory·nucl-th

Friday·March 4, 2016

12 papers—5 primary·7 cross-listed

All12Primary5Cross-lists7
  1. 01

    [Submitted on 3 Mar 2016]

    Multidimensionally-constrained relativistic mean-field study of spontaneous fission: coupling between shape and pairing degrees of freedom

    Jie Zhao · Bing-Nan Lu · Tamara Niksic · Dario Vretenar · Shan-Gui Zhou

    Studies of fission dynamics, based on nuclear energy density functionals, have shown that the coupling between shape and pairing degrees of freedom has a pronounced effect on the nonperturbative collective inertia and, therefore, on dynamic (least-action) spontaneous fission paths and half-lives. Collective potentials and nonperturbative cranking collective inertia tensors are calculated using the multidimensionally-constrained relativistic mean-field (MDC-RMF) model. Pairing correlations are treated in the BCS approximation using a separable pairing force of finite range. Pairing fluctuations are included as a collective variable using a constraint on particle-number dispersion. Fission paths are determined with the dynamic programming method by minimizing the action in multidimensional collective spaces. The dynamics of spontaneous fission of Fm and Fm are explored. Fission paths, action integrals and corresponding half-lives computed in the three-dimensional collective space of shape and pairing coordinates, using the relativistic functional DD-PC1 and a separable pairing force of finite range, are compared with results obtained without pairing fluctuations. Results for Fm are also discussed in relation with those recently obtained using the HFB model. The inclusion of pairing correlations in the space of collective coordinates favors axially symmetric shapes along the dynamic path of the fissioning system, amplifies pairing as the path traverses the fission barriers, significantly reduces the action integral and shortens the corresponding SF half-life.

    Comments:
    10 pages, 8 figures. arXiv admin note: text overlap with arXiv:1511.05689
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1603.00992 [pdf]
    PRC(2016)·83 citations
  2. 02

    [Submitted on 3 Mar 2016]

    Power counting for nuclear forces in chiral effective field theory

    Bingwei Long

    The present note summarizes the discourse on power counting issues of chiral nuclear forces, with an emphasis on renormalization-group invariance. Given its introductory nature, I will lean toward narrating a coherent point of view on the concepts, rather than covering comprehensively the development of chiral nuclear forces in different approaches.

    Comments:
    To appear in the special issue of the International Journal of Modern Physics E on "Effective Field Theory in Nuclear Physics", published version, added references
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1603.01002 [pdf]
    IJMPE(2016)·14 citations
  3. 03

    [Submitted on 3 Mar 2016]

    Isotopic yield in cold binary fission of even-even Cf isotopes

    K. P. Santhosh · Annu Cyriac · Sreejith Krishnan

    The cold binary fission of even-even 244-258Cf isotopes has been studied by taking the interacting barrier as the sum of Coulomb and proximity potential. The favorable fragment combinations are obtained from the cold valley plot (plot of driving potential vs. mass number of fragments) and by calculating the yield for charge minimized fragments. It is found that highest yield for 244,246,248Cf isotopes are for the fragments with isotope of Pb (Z=82) as one fragment, whereas for 250Cf and 252Cf isotopes the highest yield is for the fragments with isotope of Hg (Z=80) as one fragment. In the case of 254,256,258Cf isotopes the highest yield is for the fragments with Sn (Z=50) as one fragment. Thus, the fragment combinations with maximum yield reveal the role of doubly magic and near doubly magic nuclei in binary fission. It is found that asymmetric splitting is favoured for Cf isotopes with mass number A < 250 and symmetric splitting is favoured for Cf isotopes with A > 252. In the case of Cf isotope with A=252, there is an equal probability for asymmetric and symmetric splitting. The individual yields obtained for the cold fission of 252Cf isotope are compared with the experimental data taken from the {\gamma}- {\gamma}- {\gamma} coincidences technique using Gammasphere.

    Comments:
    18 pages, 9 figures in Nuclear Physics A (2016)
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1603.01162 [pdf]
    NPA(2016)·13 citations
  4. 04

    [Submitted on 3 Mar 2016]

    Neutron stars: from the inner crust to the core with the (Extended) Nambu-Jona-Lasinio model

    Helena Pais🇵🇹 · Débora P. Menezes🇧🇷 · Constança Providência🇵🇹

    Nucleonic matter is described within a su(2) extended Nambu-Jona-Lasinio model. Several parametrizations with different nuclear matter saturation properties are proposed. At subsaturation, nuclear pasta phases are calculated within two methods: the coexistence-phases approximation and the compressible liquid drop model, with the surface tension coefficient determined using a geometrical approach at zero temperature. An unified equation of state of stellar matter for the inner crust, with the nuclear pasta phases, and the core is calculated. The mass and radius of neutron stars within this framework are obtained for several families of hadronic and hybrid stars. The quark phase of hybrid stars is described within the su(3) NJL model including a vector term. Stellar macroscopic properties are in accordance with some of the recent results in the literature.

    Comments:
    13 pages, 10 figures, published version
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1603.01239 [pdf]
    PRC(2016)·27 citations
  5. 05

    [Submitted on 3 Mar 2016]

    Chiral Electroweak Currents in Nuclei

    D.O. Riska🇫🇮 · R. Schiavilla🇺🇸

    The development of the chiral dynamics based description of nuclear electroweak currents is reviewed. Gerald E. (Gerry) Brown's role in basing theoretical nuclear physics on chiral Lagrangians is emphasized. Illustrative examples of the successful description of electroweak observables of light nuclei obtained from chiral effective field theory are presented.

    Comments:
    34 pages, chapter for Gerry Brown memorial book
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1603.01253 [pdf]
    IJMPE(2017)·5 citations

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first authorsco-authorsvia INSPIRE