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Nuclear Theory·nucl-th

Friday·May 15, 2020

10 papers—3 primary·7 cross-listed

All10Primary3Cross-lists7
  1. 01

    [Submitted on 13 May 2020]

    Limitations of the Geiger-Nuttall Law in heavy cluster decay

    Omar Nagib · Ahmed M. Hamed

    Geiger-Nuttall Law is the simplest relation in radioactive decay relating the half-life and the decay energy. Initially restricted to decay of individual isotopes, generalizations unifying different isotopes and decay modes under a single set of constant coefficients were subsequently achieved. This motivates investigating to what extent such generalizations are possible. We also examine whether there exists a universal Geiger-Nuttall Law that can simultaneously describe all decay modes and nuclei including heavy clusters. We show that the validity of Geiger-Nuttall Law and its generalizations hinges on the assumption that half-life can be approximated linearly as a function of the square root of the ratio of the decay energy to the Coulomb barrier height. Systematic calculation of the ratio across the nuclear chart for 12 decay modes reveals that it varies over its whole range between 0 and 1. Consequently, no linear approximation can unify all the nuclei and decay modes under a single set of coefficients, and thus no universal Geiger-Nuttall Law is possible in contrast to previous claims. In cluster decay, the ratio varies within 0.6-1 where non-linearity becomes significant such that no generalized Geiger-Nuttall description of heavy clusters is possible. In the ongoing attempts of unification, it might be necessary to go beyond the Geiger-Nuttall Law and incorporate additional terms proportional to the decay energy and/or its square root.

    Comments:
    12 pages, 8 figures. Same as the published version. Title changed in v3 and v4 (this version)
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2005.06578 [pdf]
    PRC(2021)·3 citations
  2. 02

    [Submitted on 14 May 2020]

    Framework for Polarized Superfluid Fermion Systems

    Aurel Bulgac

    I discuss the advantages and disadvantages of several procedures, some known and some new, for constructing stationary states within the mean field approximation for a system with pairing correlations and unequal numbers spin-up and spin-down fermions, using the two chemical potentials framework. One procedure in particular appears to have significant physics advantages over previously suggested in the literature computational frameworks. Moreover, this framework is applicable to study strongly polarized superfluid fermion systems with arbitrarily large polarizations and with arbitrary total particle numbers. These methods are equally applicable to normal systems.

    Comments:
    13 pages, 5 figures, fix typos, inconsistent notations, figure labels, and a couple of numerical errors in Figs. 4b and 5a, added to additional panels to Fig. 5, extended text and references
    Subjects:
    Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas)
    arXiv:
    2005.06763 [pdf]
    1 citation
  3. 03

    [Submitted on 13 May 2020]

    Exploring the partonic phase at finite chemical potential in and out-of equilibrium

    O. Soloveva🇩🇪 · P. Moreau🇺🇸 · L. Oliva🇩🇪 · T. Song🇩🇪 · W. Cassing🇩🇪 · E.Bratkovskaya🇩🇪

    We study the influence of the baryon chemical potential on the properties of the Quark-Gluon-Plasma (QGP) in and out-of equilibrium. The description of the QGP in equilibrium is based on the effective propagators and couplings from the Dynamical QuasiParticle Model (DQPM) that is matched to reproduce the equation-of-state of the partonic system above the deconfinement temperature from lattice Quantum Chromodynamics (QCD). We calculate the transport coefficients such as the ratio of shear viscosity and bulk viscosity over entropy density , i.e., and in the plane and compare to other model results available at . The out-of equilibrium study of the QGP is performed within the Parton-Hadron-String Dynamics (PHSD) transport approach extended in the partonic sector by explicitly calculating the total and differential partonic scattering cross sections (based on the DQPM propagators and couplings) evaluated at the actual temperature and baryon chemical potential in each individual space-time cell of the partonic scattering. The traces of their dependences are investigated in different observables for relativistic heavy-ion collisions with a focus on the directed and elliptic flow coefficients in the energy range 7.7 GeV GeV.

    Comments:
    11 pages, 4 figures, contribution to the Proceedings of the 36th Winter Workshop on Nuclear Dynamics, 1-7 March 2020, Puerto Vallarta, Maxico. arXiv admin note: substantial text overlap with arXiv:2001.05395
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2005.07028 [pdf]
    J.Phys.Conf.Ser.(2020)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE