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Nuclear Theory·nucl-th

Wednesday·May 20, 2015

8 papers—4 primary·4 cross-listed

All8Primary4Cross-lists4
  1. 01

    Spin-polarized neutron matter at different orders of chiral effective field theory

    F. Sammarruca · R. Machleidt · N. Kaiser

    Spin-polarized neutron matter is studied using chiral two- and three-body forces. We focus, in particular, on predictions of the energy per particle in ferromagnetic neutron matter at different orders of chiral effective field theory and for different choices of the resolution scale. We discuss the convergence pattern of the predictions and their cutoff dependence. We explore to which extent fully polarized neutron matter behaves (nearly) like a free Fermi gas. We also consider the more general case of partial polarization in neutron matter as well as the presence of a small proton fraction. In other words, in our calculations, we vary both spin and isospin asymmetries. Confirming the findings of other microscopic calculations performed with different approaches, we report no evidence for a transition to a polarized phase of neutron matter5

    nucl-thPRC(2015)·14 citations
  2. 02

    Single universal curve for Alpha decay derived from semi-microscopic calculations

    M. Ismail · W. M. Seif · A. Y. Ellithi · A. Abdurrahman

    The universal curve is one of the simple ways to get preliminary information about the Alpha-decay half-life times of heavy nuclei. We try to find parameterization for the universal curve of Alpha decay based on semi-microscopic calculations, starting from the realistic M3Y-Reid nucleon-nucleon interaction. Within the deformed density-dependent cluster model, the penetration probability and the assault frequency are calculated using the WKB penetration probability. The deformations of daughter nuclei and the ground-state spin and parity of the involved nuclei are considered. We found that it is accurate enough to express the assault frequency, for all studied decays, either as a function of the mass number of the parent nuclei or as a constant average value. The average preformation probability of the Alpha cluster inside four groups of 166 even(Z)-even(N), 117 odd-even, 141 even-odd, and 72 odd-odd Alpha-emitters are obtained, individually. The effect of participating unpaired nucleons in the involved nuclei, as well as the influence of any differences in their ground-state spin and/or parity, appears in the obtained average values of the preformation probability. Based on the calculated WKB penetration probability, we suggested a single universal curve for Alpha decay, with only one parameter. This parameter varies according to the classified four groups. It includes the preformation probability and the average assault frequency, in addition to the pairing contribution.

    nucl-thPRC(2015)·18 citations
  3. 03

    Spurious finite-size instabilities in nuclear energy density functionals: spin channel

    A. Pastore🇫🇷 · D. Tarpanov🇵🇱 · D. Davesne🇫🇷 · J. Navarro🇪🇸

    It has been recently shown, that some Skyrme functionals can lead to non-converging results in the calculation of some properties of atomic nuclei. A previous study has pointed out a possible link between these convergence problems and the appearance of finite-size instabilities in symmetric nuclear matter (SNM) around saturation density. We show that the finite-size instabilities not only affect the ground state properties of atomic nuclei, but they can also influence the calculations of vibrational excited states in finite nuclei. We perform systematic fully-self consistent Random Phase Approximation (RPA) calculations in spherical doubly-magic nuclei. We employ several Skyrme functionals and vary the isoscalar and isovector coupling constants of the time-odd term . We determine critical values of these coupling constants beyond which the RPA calculations do not converge because RPA the stability matrix becomes non-positive.By comparing the RPA calculations of atomic nuclei with those performed for SNM we establish a correspondence between the critical densities in the infinite system and the critical coupling constants for which the RPA calculations do not converge. We find a quantitative stability criterion to detect finite-size instabilities related to the spin term of a functional. This criterion could be easily implemented into the standard fitting protocols to fix the coupling constants of the Skyrme functional.

    nucl-thPRC(2015)·18 citations
  4. 04

    Crystalline chiral condensates as a component of compact stars

    S. Carignano🇺🇸 · E.J. Ferrer🇺🇸 · V. de la Incera🇺🇸 · L. Paulucci🇧🇷

    We investigate the influence of spatially inhomogeneous chiral symmetry-breaking condensates in a magnetic field background on the equation of state for compact stellar objects. After building a hybrid star composed of nuclear and quark matter using the Maxwell construction, we find, by solving the Tolman-Oppenheimer-Volkoff equations for stellar equilibrium, that our equation of state supports stars with masses around 2 for values of the magnetic field that are in accordance with those inferred from magnetar data. The inclusion of a weak vector interaction term in the quark part allows one to reach 2 solar masses for relatively small central magnetic fields, making this composition a viable possibility for describing the internal degrees of freedom of this class of astrophysical objects.

    nucl-thastro-ph.HEhep-phPRD(2015)·48 citations

Affiliations

first authorsco-authorsvia INSPIRE