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Nuclear Theory·nucl-th

Thursday·July 25, 2019

5 papers—2 primary·3 cross-listed

All5Primary2Cross-lists3
  1. 01

    [Submitted on 24 Jul 2019]

    -wave quasiparticle resonance in neutron-rich drip-line nuclei

    Yoshihiko Kobayashi · Masayuki Matsuo

    We investigate unbound single-particle states in pair-correlated drip-line nuclei by describing a low-energy elastic scattering of a neutron in the -wave within the framework of the coordinate space Hartree-Fock-Bogolibov (Bogoliubov-de Genne) equation. Numerical study is performed for a neutron drip-line carbon isotope where the neutron orbit is located close to zero energy. Analyzing the S-matrix poles of the elastic scattering, we discuss properties of the -wave quasiparticle resonance and, in particular, behaviors characteristic to drip-line nuclei. It is found that the S-matrix has two pairs of poles; one pair appears as either a weakly bound state, a virtual state or a resonance while the other pair gives contribution analogous to a bound single-particle state. The -wave quasiparticle resonance emerges with a large variation depending on the pairing gap and the single-particle energy of the -orbit.

    Comments:
    33 pages, 17 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1907.10325 [pdf]
    PTEP(2020)·5 citations
  2. 02

    [Submitted on 24 Jul 2019]

    Towards a consistent understanding of the exotic nucleus

    Syed Afsar Abbas · Anisul Ain Usmani · Usuf Rahaman · Mohammad Ikram

    The issue of whether is doubly magical or not has been a contentious one. Fridmann {\it et al.} (Nature 435 (2005) 922) through studies of two-proton knockout reaction , presented a strong empirical evidence in support of magicity and sphericity of . However in complete conflict with this, Bastin {\it et al.} (Phys. Rev. Lett. 99 (2007) 022503) gave equally strong empirical evidences, to show that the N = 28 magicity had completely collapsed, and that was a well deformed nucleus. At present the popular consensus (Gade {\it et al.}, Phys. Rev. Lett. 122 (2019) 222501) strongly supports the latter one and discards the former one. Here, while we accept the latter experiment as being fine and good, through a careful study of an RMF model calculation, we show that actually the experimental results of Fridmann are also independently good and consistent. As per the Fridmann experiment, the sphericity and magicity of is manifested only through proton number Z=14 being a strong magic number, while the neutron magic number N=28 disappears (or goes into hiding); and still this nucleus is spherical. This is a new and amazing property manifesting itself in this exotic nucleus . In this paper we provide a consistent understanding of this novel reality within a QCD based model. This model, which has been successful in explanation of the halo phenomenon in exotic nuclei, comes forward to provide the physical reason as to why the Fridmann experiment is correct. This QCD based model shows that it is tritons, as elementary entity making up , which then provides consistency to the above amazing conclusions arising from the Fridmann experiment.

    Comments:
    5 pages, 3 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1907.10342 [pdf]
    Indian J.Pure Appl.Phys.(2020)·2 citations
  3. 03

    [Submitted on 19 Jan 2018] (cross-list from physics.ins-det)

    Maximal angular correlation in coincidences: a quantitative study

    Filipe Moura

    The measurement of the angular distribution of maximally correlated annihilation gamma rays radiated in coincidence, like those emitted from a source, is a classic experiment that is nowadays ordinarily performed in Nuclear Physics laboratory classes. For the first time we present an analytic expression for such angular distribution, which can be easily tested and confronted with the laboratory measurements.

    Comments:
    12 pages, 3 figures
    Subjects:
    Instrumentation and Detectors (physics.ins-det); Nuclear Theory (nucl-th)
    arXiv:
    1801.06573 [pdf]
    Am.J.Phys.(2019)·2 citations
  4. 04

    [Submitted on 24 Jul 2019] (cross-list from cond-mat.quant-gas)

    Complex Langevin and other approaches to the sign problem in quantum many-body physics

    Casey E. Berger🇺🇸 · Lukas Rammelmüller🇩🇪 · Andrew C. Loheac🇺🇸 · Florian Ehmann🇩🇪 · Jens Braun🇩🇪 · Joaquín E. Drut🇺🇸

    We review the theory and applications of complex stochastic quantization to the quantum many-body problem. Along the way, we present a brief overview of a number of ideas that either ameliorate or in some cases altogether solve the sign problem, including the classic reweighting method, alternative Hubbard-Stratonovich transformations, dual variables (for bosons and fermions), Majorana fermions, density-of-states methods, imaginary asymmetry approaches, and Lefschetz thimbles. We discuss some aspects of the mathematical underpinnings of conventional stochastic quantization, provide a few pedagogical examples, and summarize open challenges and practical solutions for the complex case. Finally, we review the recent applications of complex Langevin to quantum field theory in relativistic and nonrelativistic quantum matter, with an emphasis on the nonrelativistic case.

    Comments:
    68 pages, 19 figures, review article, version submitted to Physics Reports
    Subjects:
    Quantum Gases (cond-mat.quant-gas); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    1907.10183 [pdf]
    Phys.Rept.(2021)·113 citations
  5. 05

    [Submitted on 24 Jul 2019] (cross-list from physics.comp-ph)

    Reducing the complexity of finite-temperature auxiliary-field quantum Monte Carlo

    C.N. Gilbreth · S. Jensen · Y. Alhassid

    The auxiliary-field quantum Monte Carlo (AFMC) method is a powerful and widely used technique for ground-state and finite-temperature simulations of quantum many-body systems. We introduce several algorithmic improvements for finite-temperature AFMC calculations of dilute fermionic systems that reduce the computational complexity of most parts of the algorithm. This is principally achieved by reducing the number of single-particle states that contribute at each configuration of the auxiliary fields to a number that is of the order of the number of fermions. Our methods are applicable for both the canonical and grand-canonical ensembles. We demonstrate the reduced computational complexity of the methods for the homogeneous unitary Fermi gas.

    Comments:
    11 pages, 7 figures, 1 table. Changed page layout and added additional figures, clarifications in the text, and an additional appendix with a derivation of a formula in the main text. The algorithm presented is unchanged
    Subjects:
    Computational Physics (physics.comp-ph); Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
    arXiv:
    1907.10596 [pdf]
    Comput.Phys.Commun.(2021)·12 citations

Affiliations

first authorsco-authorsvia INSPIRE