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Nuclear Theory·nucl-th

Wednesday·February 9, 2022

6 papers—3 primary·3 cross-listed

All6Primary3Cross-lists3
  1. 01

    [Submitted on 7 Feb 2022]

    Finite-Volume Pionless Effective Field Theory for Few-Nucleon Systems with Differentiable Programming

    Xiangkai Sun🇺🇸 · William Detmold🇺🇸 · Di Luo🇺🇸 · Phiala E. Shanahan🇺🇸

    Finite-volume pionless effective field theory provides an efficient framework for the extrapolation of nuclear spectra and matrix elements calculated at finite volume in lattice QCD to infinite volume, and to nuclei with larger atomic number. In this work, it is demonstrated how this framework may be implemented via a set of correlated Gaussian wavefunctions optimised using differentiable programming and via solution of a generalised eigenvalue problem. This approach is shown to be significantly more efficient than a stochastic implementation of the variational method based on the same form of correlated Gaussian wavefunctions, yielding comparably accurate representations of the ground-state wavefunctions with an order of magnitude fewer terms. The efficiency of representation allows such calculations to be extended to larger systems than in previous work. The method is demonstrated through calculations of the binding energies of nuclei with atomic number in finite volume, matched to lattice QCD calculations at quark masses corresponding to MeV, and infinite-volume effective field theory calculations of systems based on this matching.

    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2202.03530 [pdf]
    PRD(2022)·12 citations
  2. 02

    [Submitted on 8 Feb 2022]

    Bubble nuclei with shape coexistence in even-even isotopes of Hf to Hg

    Yong-Beom Choi · Chang-Hwan Lee · Myeong-Hwan Mun · Youngman Kim

    The shape of a nucleus is one of fundamental nuclear properties. We perform a systematic investigation of bubble nuclei that also exhibit shape coexistence in Hf, W, Os, Pt and Hg even-even isotopes using the deformed relativistic Hartree-Bogoliubov theory in continuum. For a systematic study, we first consider nuclear bubble structures and shape coexistence separately. We confirm that deformations and pairing correlations hinder bubble structures by comparing our results with those from relativistic continuum Hartree-Bogoliubov theory that assumes spherical symmetry in nuclei. We then predict candidate isotopes with both bubble structure and shape coexistence. We observe that the depletion fraction factor that characterizes bubble structure is mostly smaller in oblate deformation than in prolate, while some isotopes such as Os have bubble structures both in oblate and prolate deformations. We compare the proton single-particle energy levels for the candidates of shape coexistence both with only prolate bubble structure and with prolate and oblate bubble structures.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2202.03871 [pdf]
    PRC(2022)·37 citations
  3. 03

    [Submitted on 8 Feb 2022]

    Nucleon-nucleon scattering up to next-to-next-to-leading order in manifestly Lorentz-invariant chiral effective field theory: peripheral phases

    Xiu-Lei Ren🇩🇪 · E. Epelbaum🇩🇪 · J. Gegelia🇩🇪

    We study the nucleon-nucleon interaction up to next-to-next-to-leading order using time-ordered perturbation theory in the framework of manifestly Lorentz-invariant chiral effective field theory. We present the two-pion exchange contribution at one-loop level, which is consistent with the corresponding non-relativistic expressions in the large-nucleon-mass limit. Using the Born series truncated at one-loop order, we calculate the phase shifts and mixing angles of the partial waves with the angular momentum . Comparing with the results of non-relativistic formulation, we find an improved description of the phase shifts for some waves such as the one. For the other partial waves, both approaches show the globally similar results.

    Comments:
    26 pages, 9 figures, matches the published version
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2202.04018 [pdf]
    PRC(2022)·13 citations
  4. 04

    [Submitted on 8 Feb 2022] (cross-list from quant-ph)

    Physical symmetries and gauge choices in the Landau problem

    Masashi Wakamatsu🇯🇵 · Akihisa Hayashi🇯🇵

    Due to a special nature of the Landau problem, in which the magnetic field is uniformly spreading over the whole two-dimensional plane, there necessarily exist three conserved quantities, i.e. two conserved momenta and one conserved orbital angular momentum for the electron, independently of the choice of the gauge potential. Accordingly, the quantum eigen-functions of the Landau problem can be obtained by diagonalizing the Landau Hamiltonian together with one of the above three conserved operators with the result that the quantum mechanical eigen-functions of the Landau problem can be written down for arbitrary gauge potential. The purpose of the present paper is to clarify the meaning of gauge choice in the Landau problem based on this gauge-potential-independent formulation, with a particular intention of unraveling the physical significance of the concept of gauge-invariant-extension of the canonical orbital angular momentum advocated in recent literature on the nucleon spin decomposition problem. At the end, our analysis is shown to disclose a physically vacuous side face of the gauge symmetry.

    Comments:
    version to appear in The European Physical Journal A
    Subjects:
    Quantum Physics (quant-ph); High Energy Physics — Phenomenology (hep-ph); Mathematical Physics (math-ph); math.MP (math.MP); Nuclear Theory (nucl-th)
    arXiv:
    2202.03592 [pdf]
    EPJA(2022)·14 citations
  5. 05

    [Submitted on 8 Feb 2022] (cross-list from hep-lat)

    Generalised Parton Distributions from Lattice Feynman-Hellmann Techniques

    Alec Hannaford-Gunn🇦🇺 · Kadir Utku Can🇬🇧 · Roger Horsley🇩🇪 · Holder Perlt🇬🇧 · Paul Rakow🇩🇪 · Gerrit Schierholz🇩🇪 · Hinnerk Stüben🇦🇺 · Ross Young🇦🇺 · James Zanotti🇦🇺

    We report on the use of Feynman-Hellmann techniques to calculate the off-forward Compton amplitude (OFCA) in lattice QCD. At leading-twist, the Euclidean OFCA is parameterised by the Mellin moments of generalised parton distributions (GPDs). Hence we extract GPD moments for two values of the soft momentum transfer, and zero-skewness kinematics at an unphysical pion mass of . This includes the first determination of the moments.

    Comments:
    9 pages, 3 figures
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2202.03662 [pdf]
    PoS(2022)·4 citations
  6. 06

    [Submitted on 8 Feb 2022] (cross-list from hep-ph)

    Spin waves in spin hydrodynamics

    Victor E. Ambrus🇩🇪 · Radoslaw Ryblewski🇵🇱 · Rajeev Singh🇵🇱

    The propagation properties of spin degrees of freedom are analyzed in the framework of relativistic hydrodynamics with spin based on the de Groot--van Leeuwen--van Weert definitions of the energy-momentum and spin tensors. We derive the analytical expression for the spin wave velocity for arbitrary statistics and show that it goes to half the speed of light in the ultra-relativistic limit. We find that only the transverse degrees of freedom propagate, analogously to electromagnetic waves. Finally, we consider the effect of dissipative corrections and calculate the damping coefficients for the case of Maxwell-Jüttner statistics.

    Comments:
    11 pages; 3 captioned figures; published version
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2202.03952 [pdf]
    PRD(2022)·28 citations

Affiliations

first authorsco-authorsvia INSPIRE