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Nuclear Theory·nucl-th

Thursday·August 4, 2016

6 papers—4 primary·2 cross-listed

All6Primary4Cross-lists2
  1. 01

    [Submitted on 2 Aug 2016]

    On the spin excitation energy of the nucleon in the Skyrme model

    C. Adam🇪🇸 · J. Sanchez-Guillen🇪🇸 · A. Wereszczynski🇵🇱

    In the Skyrme model of nucleons and nuclei, the spin excitation energy of the nucleon is traditionally calculated by a fit of the rigid rotor quantization of spin/isospin of the fundamental Skyrmion (the hedgehog) to the masses of the nucleon and the Delta resonance. The resulting, quite large spin excitation energy of the nucleon of about is, however, rather difficult to reconcile with the small binding energies of physical nuclei, among other problems. Here we argue that a more reliable value for the spin excitation energy of the nucleon, compatible with many physical constraints, is about . The fit of the rigid rotor to the Delta, on the other hand, is problematic in any case, because it implies the use of a nonrelativistic method for a highly relativistic system.

    Comments:
    Latex, 8 pages, no figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1608.00979 [pdf]
    IJMPE(2016)·8 citations
  2. 02

    [Submitted on 2 Aug 2016]

    Chiral Magnetic Effect Task Force Report

    Vladimir Skokov🇺🇸 · Paul Sorensen🇺🇸 · Volker Koch🇺🇸 · Soeren Schlichting🇺🇸 · Jim Thomas🇺🇸 · Sergei Voloshin🇺🇸 · Gang Wang🇺🇸 · Ho-Ung Yee🇺🇸

    In this report, we briefly examine the current status of the study of the chiral magnetic effect including theory and experimental progress. We recommend future strategies for resolving uncertainties in interpretation including recommendations for theoretical work, recommendations for measurements based on data collected in the past five years, and recommendations for beam use in the coming years of RHIC. We have specifically investigated the case for colliding nuclear isobars (nuclei with the same mass but different charge) and find the case compelling. We recommend that a program of nuclear isobar collisions to isolate the chiral magnetic effect from background sources be placed as a high priority item in the strategy for completing the RHIC mission.

    Comments:
    28 pages, 7 figures; Task Force Report on Chiral Magnetic Effect; v2: references added, minor corrections
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1608.00982 [pdf]
    CPC(2017)·160 citations
  3. 03

    [Submitted on 3 Aug 2016]

    Probing the resonance of Dirac particle by the application of complex momentum representation

    Niu Li🇨🇳 · Min Shi🇨🇳 · Jian-You Guo🇨🇳 · Zhong-Ming Niu🇨🇳 · Haozhao Liang🇯🇵

    Resonance plays critical roles in the formation of many physical phenomena, and several methods have been developed for the exploration of resonance. In this work, we propose a new scheme for resonance by solving the Dirac equation in complex momentum representation, in which the resonant states are exposed clearly in complex momentum plane and the resonance parameters can be determined precisely without imposing unphysical parameters. Combining with the relativistic mean-field theory, this method is applied to probe the resonances in Sn with the energies, widths, and wavefunctions being obtained. Comparing with other methods, this method is not only very effective for narrow resonances, but also can be reliably applied to broad resonances.

    Comments:
    6 pages, 5 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Theory (hep-th); Nuclear Experiment (nucl-ex); Quantum Physics (quant-ph)
    arXiv:
    1608.01046 [pdf]
    PRL(2016)·60 citations
  4. 04

    [Submitted on 3 Aug 2016]

    Quartetting in odd-odd self-conjugate nuclei

    M. Sambataro · N. Sandulescu

    We provide a description of odd-odd self-conjugate nuclei in the sd shell in a formalism of collective quartets and pairs. Quartets are four-body structures carrying isospin T=0 while pairs can have either T=0 or T=1. Both quartets and pairs are labeled by the angular momentum J and they are chosen so as to describe the lowest states of 20Ne (quartets) and the lowest T=0 and T=1 states of 18F (pairs). We carry out configuration interaction calculations in spaces built by one quartet and one pair for 22Na and by two quartets and one pair for 26Al. The spectra that are generated are in good agreement with the shell model and experimental ones. These calculations confirm the relevance of quartetting in the structure of N=Z nuclei that had already emerged in previous studies of the even-even systems and highlight the role of J>0 quartets in the composition of the odd-odd spectra.

    Comments:
    15 pages, 6 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1608.01105 [pdf]
    PLB(2016)·14 citations
  5. 05

    [Submitted on 3 Aug 2016] (cross-list from astro-ph.HE)

    Gravitational wave asteroseismology with protoneutron stars

    Hajime Sotani🇯🇵 · Tomoya Takiwaki🇯🇵

    We examine the time evolution of the frequencies of the gravitational wave after the bounce within the framework of relativistic linear perturbation theory using the results of one dimensional numerical simulations of core-collapse supernovae. Protoneutron star models are constructed in such a way that the mass and radius of protoneutron star become equivalent to the results obtained from the numerical simulations. Then, we find that the frequencies of gravitational waves radiating from protoneutron stars strongly depend on the mass and radius of protoneutron stars, but almost independently of the profiles of electron fraction and entropy per baryon inside the star. Additionally, we find that the frequencies of gravitational waves can be characterized by the square root of the average density of protoneutron star irrespectively the progenitor models, which are completely different from the empirical formula for cold neutron stars. The dependence of the spectra on the mass and radius is different from that of the -mode: the oscillations around the surface of protoneutron stars due to the convection and the standing accretion-shock instability. Careful observations of the these modes of gravitational waves can determine the evolution of the mass and radius of protoneutron stars after core-bounce. Furthermore, the expected frequencies of gravitational waves are around a few hundred hertz in the early stage after bounce, which must be a good candidate for the ground-based gravitational wave detectors.

    Comments:
    accepted for publication in PRD
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
    arXiv:
    1608.01048 [pdf]
    PRD(2016)·81 citations
  6. 06

    [Submitted on 3 Aug 2016] (cross-list from astro-ph.HE)

    Role of nuclear physics in oscillations of magnetars

    Rana Nandi🇩🇪 · Prasanta Char🇮🇳 · Debarati Chatterjee🇫🇷 · Debades Bandyopadhyay🇮🇳

    Strong magnetic fields have important effects on the crustal properties of magnetars. Here we study the magneto-elastic oscillations of magnetars taking into consideration the effect of strong magnetic fields on the crustal composition (magnetised crust). We calculate global magneto-elastic (GME) modes as well as modes confined to the crust (CME) only. The composition of the crust directly affects its shear modulus which we calculate using three different nucleon-nucleon interactions: SLy4, SkM and Sk272. The shear modulus of the crust is found to be enhanced in strong magnetic fields G for all those Skyrme interactions. It is noted that the shear modulus of the crust for the SLy4 interaction is much higher than those of the SkM and Sk272 interactions in presence of magnetic fields or not. Though we do not find any appreciable change in frequencies of fundamental GME and CME modes with and without magnetised crusts, frequencies of first overtones of CME modes are significantly affected in strong magnetic fields G. However, this feature is not observed in frequencies of first overtones of GME modes. As in earlier studies, it is also noted that the effects of crusts on frequencies of both types of maneto-elastic modes disappear when the magnetic field reaches the critical field ( G). Frequencies of GME and CME modes calculated with magnetised crusts based on all three nucleon-nucleon interactions, stellar models and magnetic fields, are compared with frequencies of observed quasi-periodic oscillations (QPOS) in SGR 1806-20 and SGR1900+14. As in earlier studies, this comparison indicates that GME modes are essential to explain all the frequencies as CME modes can explain only the higher frequencies.

    Comments:
    28 pages, 8 figures, accepted for publication in PRC. arXiv admin note: substantial text overlap with arXiv:1207.3247
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
    arXiv:
    1608.01241 [pdf]
    PRC(2016)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE