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Nuclear Theory·nucl-th

Thursday·January 20, 2022

9 papers—4 primary·5 cross-listed

All9Primary4Cross-lists5
  1. 01

    [Submitted on 18 Jan 2022]

    Angular-momentum projection in coupled-cluster theory: structure of Mg

    G. Hagen · S. J. Novario🇺🇸 · Z. H. Sun🇺🇸 · T. Papenbrock🇺🇸 · G. R. Jansen🇺🇸 · J. G. Lietz🇺🇸 · T. Duguet🇫🇷 · A. Tichai🇩🇪

    Single-reference coupled-cluster theory is an accurate and affordable computational method for the nuclear many-body problem. For open-shell nuclei, the reference state typically breaks rotational invariance and angular momentum must be restored as a good quantum number. We perform angular-momentum projection after variation and employ the disentangled coupled-cluster formalism and a Hermitian approach. We compare our results with benchmarks for Be and Ne using a two-nucleon interaction from chiral effective field theory and for -shell nuclei within the traditional shell model. We compute the rotational band in the exotic nucleus Mg and find agreement with data.

    Comments:
    23 pages, 12 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2201.07298 [pdf]
    PRC(2022)·91 citations
  2. 02

    [Submitted on 18 Jan 2022]

    Efficient emulation of relativistic heavy ion collisions with transfer learning

    Dananjaya Liyanage🇺🇸 · Yi Ji🇺🇸 · Derek Everett🇺🇸 · Matthew Heffernan🇨🇦 · Ulrich Heinz🇺🇸 · Simon Mak🇺🇸 · Jean-Francois Paquet🇺🇸

    Measurements from the Large Hadron Collider (LHC) and the Relativistic Heavy Ion Collider (RHIC) can be used to study the properties of quark-gluon plasma. Systematic constraints on these properties must combine measurements from different collision systems and methodically account for experimental and theoretical uncertainties. Such studies require a vast number of costly numerical simulations. While computationally inexpensive surrogate models ("emulators") can be used to efficiently approximate the predictions of heavy ion simulations across a broad range of model parameters, training a reliable emulator remains a computationally expensive task. We use transfer learning to map the parameter dependencies of one model emulator onto another, leveraging similarities between different simulations of heavy ion collisions. By limiting the need for large numbers of simulations to only one of the emulators, this technique reduces the numerical cost of comprehensive uncertainty quantification when studying multiple collision systems and exploring different models.

    Comments:
    15 pages, 6 figures, journal article
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2201.07302 [pdf]
    PRC(2022)·25 citations
  3. 03

    [Submitted on 19 Jan 2022]

    Competition between weak and alpha-decay modes in superheavy nuclei

    Pedro Sarriguren

    The competition between alpha- and beta+/EC-decay modes is studied systematically in nuclei along the alpha-decay chains following the synthesis of superheavy nuclei with Z = 119 and Z = 120. A microscopic approach based on deformed self-consistent Hartree-Fock mean-field calculations with Skyrme forces and pairing correlations is used to describe the beta+ and electron capture weak decays, whereas the alpha-decay is estimated from existing phenomenological expressions. It is shown that alpha-decay is in most cases the dominant decay mode, but interesting instances are identified where the half-lives are comparable, opening the possibility of new pathways towards more neutron-rich nuclei in this region.

    Comments:
    9 pages, 7 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2201.07476 [pdf]
    PRC(2022)·7 citations
  4. 04

    [Submitted on 19 Jan 2022]

    S-wave pion condensation in symmetric nuclear matter

    D. N. Voskresensky (JINR, Dubna, Russia)🇷🇺

    S-wave pion-nucleon interactions in the linear sigma model, and in Manohar-Georgi and Gasser-Sainio-Svarc models with finite number of terms in Lagrangians, as well as in a general phenomenological approach are reviewed. Subtleties associated with the current algebra theorems and field redefinitions are discussed. In the first and third models most likely the s-wave pion condensation in the isospin-symmetric matter does not occur at least up to high densities, whereas within the second model it may appear already at moderate densities. In the phenomenological approach two parameterizations of the s-wave pion-nucleon scattering amplitude and the pion polarization operator used in the literature are considered. The first parameterization employs the off-mass-shell amplitude and allows to fulfil the current algebra theorems. Using it the s-wave pion polarization operator in the isospin-symmetric matter is reconstructed within the gas approximation. With this pion polarization operator the s-wave pion condensation in the isospin-symmetric matter does not occur at least up to high densities. Second parameterization uses the on-mass-shell pion-nucleon scattering amplitude and does not satisfy the Adler and Weinberg conditions. With such a parameterization most likely the s-wave pion condensation in the isospin-symmetric matter may occur already at the nucleon density , where is the density of the atomic nucleus, that should result in observable effects. Both parameterizations allow to successfully describe the pion atom data.

    Comments:
    15 pages, 2 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2201.07536 [pdf]
    PRD(2022)·12 citations

Affiliations

first authorsco-authorsvia INSPIRE