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Nuclear Theory·nucl-th

Friday·June 4, 2021

5 papers—1 primary·4 cross-listed

All5Primary1Cross-lists4
  1. 01

    [Submitted on 2 Jun 2021]

    Efimov resonances above four-boson threshold

    A. Deltuva

    Four-boson Efimov physics is well known in the negative energy regime but far less above the four-body breakup threshold. The part of this region with negative two-boson scattering length is studied solving rigorous four-particle scattering equations for transition operators in the momentum space. Moving away from the unitary limit the Efimov tetramers evolve from unstable bound states into resonances. Their energies and widths are studied as functions of the two-boson scattering length; a universal behavior is established and given in a dimensionless representation. The Efimov tetramers have finite width in the whole regime; they broaden rapidly in the resonance regime but remain narrower than the associated trimer. The resonant behavior is most clearly seen in the four-particle recombination rate.

    Comments:
    5+ pages, to be published in Phys. Rev. C
    Subjects:
    Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas); Atomic Physics (physics.atom-ph)
    arXiv:
    2106.01458 [pdf]
    PRC(2021)·1 citation
  2. 02

    [Submitted on 25 May 2021] (cross-list from physics.flu-dyn)

    Chiral propulsion: the method of effective boundary conditions

    Leonid A. Korneev · Dmitri E. Kharzeev · Alexander G. Abanov

    We propose to apply an "effective boundary condition" method to the problem of chiral propulsion. For the case of a rotating helix moving through a fluid at a low Reynolds number, the method amounts to replacing the original helix (in the limit of small pitch) by a cylinder, but with a special kind of partial slip boundary conditions replacing the non-slip boundary conditions on the original helix. These boundary conditions are constructed to reproduce far-field velocities of the original problem, and are defined by a few parameters (slipping lengths) that can be extracted from a problem in planar rather than cylindrical geometry. We derive the chiral propulsion coefficients for spirals, helicoids, helically modulated cylinders, and some of their generalizations using the introduced method. In the case of spirals, we compare our results with the ones derived by Lighthill and find a very good agreement. The proposed method is general and can be applied to any helical shape in the limit of a small pitch. We have established that for a broad class of helical surfaces the dependence of the chiral propulsion on the helical angle is universal, with the maximal propulsion achieved at the universal angle .

    Comments:
    18 pages, 6 figures
    Subjects:
    Fluid Dynamics (physics.flu-dyn); Nuclear Theory (nucl-th)
    arXiv:
    2105.12181 [pdf]
    Phys.Fluids(2021)·0 citations
  3. 03

    [Submitted on 1 Jun 2021] (cross-list from hep-ph)

    The proton radius (puzzle?) and its relatives

    Clara Peset🇩🇪 · Antonio Pineda🇪🇸 · Oleksandr Tomalak🇺🇸

    We review determinations of the electric proton charge radius from a diverse set of low-energy observables. We explore under which conditions it can be related to Wilson coefficients of appropriate effective field theories. This discussion is generalized to other low-energy constants. This provides us with a unified framework to deal with a set of low-energy constants of the proton associated with its electromagnetic interactions. Unambiguous definitions of these objects are given, as well as their relation with expectation values of QCD operators. We show that the proton radius obtained from spectroscopy and lepton-proton scattering (when both the lepton and proton move with nonrelativistic velocities) is related to the same object of the underlying field theory with precision. The model dependence of these analyses is discussed. The prospects of constructing effective field theories valid for the kinematic configuration of present, or near-future, lepton-proton scattering experiments are discussed.

    Comments:
    70 pages, 14 figures. Minor modifications to meet journal version. References added
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
    arXiv:
    2106.00695 [pdf]
    PPNP(2021)·33 citations
  4. 04

    [Submitted on 2 Jun 2021] (cross-list from quant-ph)

    Worldline Path Integrals for Gauge Fields and Quantum Computing

    Yuan Feng🇺🇸 · Michael McGuigan🇺🇸

    We study different aspects the worldline path integrals with gauge fields using quantum computing. We use the Variational Quantum Eigensolver (VQE) and Evolution of Hamiltonian (EOH) quantum algorithms and IBM QISKit to perform our computations. We apply these methods to the path integral of a particle moving in a Abelian and non-Abelian background gauge field associated with a constant magnetic field and the field of a chromo-magnetic field. In all cases we found excellent agreement with the classical computation. We also discuss the insertion of vertex operators into the worldline path integrals to study scattering and show how to represent them using unitary operators and quantum gates on near term quantum computers.

    Comments:
    added references
    Subjects:
    Quantum Physics (quant-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2106.01398 [pdf]
    0 citations
  5. 05

    [Submitted on 3 Jun 2021] (cross-list from nucl-ex)

    Neutron occupancies and single-particle energies across the stable tin isotopes

    S. V. Szwec🇬🇧 · D. K. Sharp🇬🇧 · B. P. Kay🇺🇸 · S. J. Freeman🇬🇧 · J. P. Schiffer🇺🇸 · P. Adsley🇫🇷 · C. Binnersley🇬🇧 · N. de Séréville🇫🇷 · T. Faestermann🇩🇪 · R. F. Garcia Ruiz🇬🇧 · F. Hammache🇫🇷 · R. Hertenberger🇩🇪 and 5 other authors

    The occupancies and vacancies of the valence neutron orbitals across the stable tin isotopic chain from have been determined. These were inferred from the cross sections of neutron-adding and -removing reactions. In each case, the reactions were chosen to have good angular-momentum matching for transfer to the low- and high- orbitals present in this valence space. These new data are compared to older systematic studies. The effective single-neutron energies are determined by combining information from energy centroids determined from the adding and removing reactions. Two of the five orbitals are nearly degenerate, below , and approximately two MeV more bound than the other three, which are also degenerate.

    Comments:
    11 pages, 10 figures
    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2106.01848 [pdf]
    PRC(2021)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE