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Nuclear Theory·nucl-th

Wednesday·August 17, 2016

7 papers—4 primary·3 cross-listed

All7Primary4Cross-lists3
  1. 05

    [Submitted on 15 Aug 2016] (cross-list from nucl-ex)

    Ordering of the and proton levels in light nuclei

    C. R. Hoffman · B. P. Kay · J. P. Schiffer

    A survey of the available single-proton data in nuclei, along with calculations using a Woods-Saxon potential, show that the ordering of the and proton orbitals are determined primarily by the proximity of the -state proton energy to the Coulomb barrier. This is analogous to the dependence of the corresponding neutron orbitals in proximity to the neutron threshold, that was previously discussed.

    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1608.04427 [pdf]
    PRC(2016)·17 citations
  2. 06

    [Submitted on 16 Aug 2016] (cross-list from hep-ph)

    Applicability of the Wigner functional approach to evolution of quantum fields

    Andrey Leonidov🇷🇺 · Anna Radovskaya🇷🇺

    Evolution of highly excited quantum field is considered in the framework of Keldysh formalism . It is demonstrated that leading order (LO) term of semiclassical approximation appears as well-known Classical Statistical Approximation (CSA). In simple case of spatially homogeneous scalar field analytical expressions for leading and next-to-leading (NLO) order are presented. It is shown that the range of applicability of CSA strongly depends on the properties of the initial state of the system

    Comments:
    Based on talk given at the 19th Intenational Seminar QUARKS 2016
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1608.04580 [pdf]
    EPJ Web Conf.(2016)·6 citations
  3. 07

    [Submitted on 16 Aug 2016] (cross-list from astro-ph.CO)

    Stellar Helium Burning in Other Universes: A solution to the triple alpha fine-tuning problem

    Fred C. Adams · Evan Grohs

    Motivated by the possible existence of other universes, with different values for the fundamental constants, this paper considers stellar models in universes where Be is stable. Many previous authors have noted that stars in our universe would have difficulty producing carbon and other heavy elements in the absence of the well-known C resonance at 7.6 MeV. This resonance is necessary because Be is unstable in our universe, so that carbon must be produced via the triple alpha reaction to achieve the requisite abundance. Although a moderate change in the energy of the resonance (200 -- 300 keV) will indeed affect carbon production, an even smaller change in the binding energy of beryllium ( keV) would allow Be to be stable. A stable isotope with would obviate the need for the triple alpha process in general, and the C resonance in particular, for carbon production. This paper explores the possibility that Be can be stable in other universes. Simple nuclear considerations indicate that bound states can be realized, with binding energy MeV, if the fundamental constants vary by a percent. In such cases, Be can be synthesized through helium burning, and C can be produced later through nuclear burning of beryllium. This paper focuses on stellar models that burn helium into beryllium; once the universe in question has a supply of stable beryllium, carbon production can take place during subsequent evolution in the same star or in later stellar generations. Using both a semi-analytic stellar structure model as well as a state-of-the-art stellar evolution code, we find that viable stellar configurations that produce beryllium exist over a wide range of parameter space. Finally, we demonstrate that carbon can be produced during later evolutionary stages.

    Comments:
    48 pages, 9 figures, accepted to Astroparticle Physics
    Subjects:
    Cosmology and Nongalactic Astrophysics (astro-ph.CO); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
    arXiv:
    1608.04690 [pdf]
    Astropart.Phys.(2017)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE