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Nuclear Theory·nucl-th

Wednesday·June 15, 2016

8 papers—4 primary·4 cross-listed

All8Primary4Cross-lists4
  1. 01

    [Submitted on 14 Jun 2016]

    Density dependence of the nuclear energy-density functional

    Panagiota Papakonstantinou · Tae-Sun Park · Yeunhwan Lim · Chang Ho Hyun

    The explicit density (rho) dependence in the coupling coefficients of the non-relativistic nuclear energy-density functional (EDF) encodes effects of three-nucleon forces and dynamical correlations. The necessity for a coupling coefficient in the form of a small fractional power of rho is empirical and the power often chosen arbitrarily. Consequently, precision-oriented parameterisations risk overfitting and loss of predictive power. Observing that the Fermi momentum kF~rho^1/3 is a key variable in Fermi systems, we examine if a power hierarchy in kF can be inferred from the properties of homogeneous matter in a domain of densities which is relevant for nuclear structure and neutron stars. For later applications we want to determine an EDF that is of good quality but not overtrained. We fit polynomial and other functions of rho^1/3 to existing microscopic calculations of the energy of symmetric and pure neutron matter and analyze the fits. We select a form and parameter set which we found robust and examine the parameters' naturalness and the resulting extrapolations. A statistical analysis confirms that low-order terms like rho^1/3 and rho^2/3 are the most relevant ones. It also hints at a different power hierarchy for symmetric vs. pure neutron matter, supporting the need for more than one rho^a terms in non-relativistic EDFs. The EDF we propose accommodates adopted properties of nuclear matter near saturation. Importantly, its extrapolation to dilute or asymmetric matter reproduces a range of existing microscopic results, to which it has not been fitted. It also predicts neutron-star properties consistent with observations. The coefficients display naturalness. Once determined for homogeneous matter, EDFs of the present form can be mapped onto Skyrme-type ones for use in nuclei. The statistical analysis can be extended to higher orders and for different ab initio calculations.

    Comments:
    14 pages, 4 figures; v2: extended version
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1606.04219 [pdf]
    PRC(2018)·55 citations
  2. 02

    [Submitted on 14 Jun 2016]

    Nuclear in-medium effects on dynamics in proton-nucleus collisions

    Jie Chen🇨🇳 · Zhao-Qing Feng🇨🇳 · Jian-Song Wang🇨🇳

    The dynamics of meson produced in proton-induced nuclear reactions via the decay of N has been investigated within the Lanzhou quantum molecular dynamics transport model (LQMD). The in-medium modifications of the production in dense nuclear matter are included in the model, in which an attractive -nucleon potential is implemented. The impact of the optical potential on the dynamics is investigated. It is found that the attractive potential leads to the reduction of high-momentum (kinetic energy) production from the spectra of momentum distributions and inclusive cross sections and increasing the reabsorption process by surrounding nucleons.

    Comments:
    5 pages, 4 figures. arXiv admin note: text overlap with arXiv:1509.04792
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1606.04379 [pdf]
    Nucl.Sci.Tech.(2016)·14 citations
  3. 03

    [Submitted on 14 Jun 2016]

    Formation of Selfbound States in a One-Dimensional Nuclear Model -- A Renormalization Group based Density Functional Study

    Sandra Kemler · Martin Pospiech · Jens Braun

    In nuclear physics, Density Functional Theory (DFT) provides the basis for state-of-the art studies of ground-state properties of heavy nuclei. However, the direct relation of the density functional underlying these calculations and the microscopic nuclear forces is not yet fully understood. We present a combination of DFT and Renormalization Group (RG) techniques which allows to study selfbound many-body systems from microscopic interactions. We discuss its application with the aid of systems of identical fermions interacting via a long-range attractive and short-range repulsive two-body force in one dimension. We compute ground-state energies, intrinsic densities, and density correlation functions of these systems and compare our results to those obtained from other methods. In particular, we show how energies of excited states as well as the absolute square of the ground-state wave function can be extracted from the correlation functions within our approach. The relation between many-body perturbation theory and our DFT-RG approach is discussed and illustrated with the aid of the calculation of the second-order energy correction for a system of identical fermions interacting via a general two-body interaction. Moreover, we discuss the control of spuriously emerging fermion self-interactions in DFT studies within our framework. In general, our approach may help to guide the development of energy functionals for future quantitative DFT studies of heavy nuclei from microscopic interactions.

    Comments:
    37 pages, 7 figures
    Subjects:
    Nuclear Theory (nucl-th); cond-mat.other (cond-mat.other); Quantum Gases (cond-mat.quant-gas)
    arXiv:
    1606.04388 [pdf]
    J.Phys.G(2017)·25 citations
  4. 04

    [Submitted on 14 Jun 2016]

    Double-step truncation procedure for large-scale shell-model calculations

    L. Coraggio · A. Gargano · N. Itaco

    We 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, so 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 an 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 and five proton and neutron single-particle orbitals outside 88Sr, respectively. 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.

    Comments:
    10 pages, 15 figures, to be published in Physical Review C
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1606.04399 [pdf]
    PRC(2016)·26 citations

Affiliations

first authorsco-authorsvia INSPIRE