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Nuclear Theory·nucl-th

Thursday·September 7, 2017

4 papers—1 primary·3 cross-listed

All4Primary1Cross-lists3
  1. 01

    [Submitted on 5 Sept 2017]

    Electric fields at finite temperature

    A. Bermudez Manjarres🇨🇴 · N. G. Kelkar🇨🇴 · Marek Nowakowski🇨🇴

    Partial differential equations for the electric potential at finite temperature, taking into account the thermal Euler-Heisenberg contribution to the electromagnetic Lagrangian are derived. This complete temperature dependence introduces quantum corrections to several well known equations such as the Thomas-Fermi and the Poisson-Boltzmann equation. Our unified approach allows at the same time to derive other similar equations which take into account the effect of the surrounding heat bath on electric fields. We vary our approach by considering a neutral plasma as well as the screening caused by electrons only. The effects of changing the statistics from Fermi-Dirac to the Tsallis statistics and including the presence of a magnetic field are also investigated. Some useful applications of the above formalism are presented.

    Comments:
    28 pages
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1709.01615 [pdf]
    Annals Phys.(2017)·5 citations
  2. 02

    [Submitted on 5 Sept 2017] (cross-list from hep-lat)

    Baryon magnetic moments: Symmetries and relations

    Assumpta Parreno🇪🇸 · Martin J. Savage🇺🇸 · Brian C. Tiburzi🇺🇸 · Jonas Wilhelm🇩🇪 · Emmanuel Chang🇺🇸 · William Detmold🇺🇸 · Kostas Orginos🇺🇸

    Magnetic moments of the octet baryons are computed using lattice QCD in background magnetic fields, including the first treatment of the magnetically coupled Sigma-Lambda system. Although the computations are performed for relatively large values of the up and down quark masses, we gain new insight into the symmetries and relations between magnetic moments by working at a three-flavor mass-symmetric point. While the spin-flavor symmetry in the large Nc limit of QCD is shared by the naive constituent quark model, we find instances where quark model predictions are considerably favored over those emerging in the large Nc limit. We suggest further calculations that would shed light on the curious patterns of baryon magnetic moments.

    Comments:
    8 pages, 5 figures, talk given at Lattice 2017, the 35th International Symposium on Lattice Field Theory, Granada, Spain, 18-24 June 2017
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1709.01564 [pdf]
    EPJ Web Conf.(2018)·3 citations
  3. 03

    [Submitted on 6 Sept 2017] (cross-list from gr-qc)

    General Relativistic effects in the structure of massive white dwarfs

    G.A. Carvalho · R.M. Marinho Jr · M. Malheiro

    In this work we investigate the structure of white dwarfs using the Tolman-Oppenheimer-Volkoff equations and compare our results with those obtained from Newtonian equations of gravitation in order to put in evidence the importance of General Relativity (GR) for the structure of such stars. We consider in this work for the matter inside white dwarfs two equations of state, frequently found in the literature, namely, the Chandrasekhar and Salpeter equations of state. We find that using Newtonian equilibrium equations, the radii of massive white dwarfs () are overestimated in comparison with GR outcomes. For a mass of the white dwarf radius predicted by GR is about 33\% smaller than the Newtonian one. Hence, in this case, for the surface gravity the difference between the general relativistic and Newtonian outcomes is about 65\%. We depict the general relativistic mass-radius diagrams as , where , , and are parameters obtained from a fitting procedure of the numerical results and , being the radius of the Sun in km. Lastly, we point out that GR plays an important role to determine any physical quantity that depends, simultaneously, on the mass and radius of massive white dwarfs.

    Comments:
    To be published in General Relativity and Gravitation
    Subjects:
    General Relativity and Quantum Cosmology (gr-qc); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
    arXiv:
    1709.01635 [pdf]
    Gen.Rel.Grav.(2018)·40 citations
  4. 04

    [Submitted on 6 Sept 2017] (cross-list from hep-ph)

    Unitarity Analyses of Elastic Scattering Amplitudes

    Yu-Fei Wang🇨🇳

    The pion - nucleon scattering phase shifts in and waves are analyzed using PKU unitarization approach that can separate the phase shifts into different contributions from poles and branch cuts. It is found that in and channels, there exist large and positive missing contributions when one compares the phase shift from known resonances plus branch cuts with the experimental data, which indicates that those two channels may contain sizable effects from and shadow poles. Those results are obtained using tree level results of the amplitude.

    Comments:
    4 pages, 2 figures (the first figure contains 6 sub-figures), from proceedings of the 11th APCTP - BLTP JINR - PNPI NRC KI - SPbU Joint Workshop (held in Saint-Petersburg in July 23-28th)
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1709.01647 [pdf]
    Phys.Part.Nucl.Lett.(2018)·0 citations

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first authorsco-authorsvia INSPIRE