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Nuclear Theory·nucl-th

Friday·May 7, 2021

5 papers—3 primary·2 cross-listed

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  1. 01

    [Submitted on 6 May 2021]

    Violation of energy conditions and entropy production in holographic Bjorken flow

    Romulo Rougemont🇧🇷 · Jorge Noronha🇺🇸 · Willians Barreto🇧🇷 · Gabriel S. Denicol🇧🇷 · Travis Dore🇺🇸

    We demonstrate that a Bjorken expanding strongly coupled Supersymmetric Yang-Mills plasma can display dynamically-driven violations of the dominant and also the weak energy condition during hydrodynamization. In addition, we find that a period of vanishing entropy production in far-from-equilibrium stages induces later violations of the dominant energy condition in the strongly coupled plasma. Such violations cannot occur in a classical description of hydrodynamization and suggest that the inclusion of quantum effects in transport can lead to new phenomena in these regimes, even for systems without anomalies or spin.

    Comments:
    9 pages, 1 figure; v3: to appear in Physical Review D
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
    arXiv:
    2105.02378 [pdf]
    PRD(2021)·16 citations
  2. 02

    [Submitted on 6 May 2021]

    Machine learning the nuclear mass

    Zepeng Gao🇨🇳 · Yongjia Wang🇨🇳 · Hongliang Lü🇨🇳 · Qingfeng Li🇨🇳 · Caiwan Shen🇨🇳 · Ling Liu🇨🇳

    Background: The masses of about 2500 nuclei have been measured experimentally, however more than 7000 isotopes are predicted to exist in the nuclear landscape from H (Z=1) to Og (Z=118) based on various theoretical calculations. Exploring the mass of the remains is a hot topic in nuclear physics. Machine learning has been served as a powerful tool in learning complex representations of big data in many fields. Purpose: We use Light Gradient Boosting Machine (LightGBM) which is a highly efficient machine learning algorithm to predict the masses of unknown nuclei and to explore the nuclear landscape in neutron-rich side from learning the measured nuclear masses. Results: By using the experimental data of 80 percent of known nuclei as the training dataset, the root mean square deviation (RMSD) between the predicted and the experimental binding energy of the remaining 20% is about 0.234 MeV, 0.213 MeV, 0.170 MeV, and 0.222 MeV for the LightGBM-refined LDM, DZ, WS4, and FRDM models, respectively. These values are of about 90%, 65%, 40%, and 60% smaller than the corresponding origin mass models. The RMSD for 66 newly measured nuclei that appeared in AME2020 is also significantly improved on the same foot. One-neutron and two-neutron separation energies predicted by these refined models are in consistence with several theoretical predictions based on various physical models. Conclusions: LightGBM can be used to refine theoretical nuclear mass models so as to predict the binding energy of unknown nuclei. Moreover, the correlation between the input characteristic quantities and the output can be interpreted by SHapley Additive exPlanations (SHAP, a popular explainable artificial intelligence tool), this may provide new insights on developing theoretical nuclear mass models.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2105.02445 [pdf]
    Nucl.Sci.Tech.(2021)·77 citations
  3. 03

    [Submitted on 6 May 2021]

    Nuclear matrix elements of neutrinoless double- decay in the triaxial projected shell model

    Y. K. Wang🇨🇳 · P. W. Zhao🇨🇳 · J. Meng🇨🇳

    The nuclear matrix elements of neutrinoless double- decay for nuclei Ge, Se, Mo, Te, and Nd are studied within the triaxial projected shell model, which incorporates simultaneously the triaxial deformation and quasiparticle configuration mixing. The low-lying spectra and the values are reproduced well. The effects of the quasiparticles configuration mixing, the triaxial deformation, and the closure approximation on the nuclear matrix elements are studied in detail. For nuclei Ge, Se, Mo, Te, and Nd, the nuclear matrix elements are respectively reduced by the quasiparticle configuration mixing by 6%, 7%, 2%, 3%, and 4%, and enhanced by the odd-odd intermediate states by 7%, 4%, 11%, 20%, and 14%. Varying the triaxial deformation from to for the mother and daughter nuclei, the nuclear matrix elements change by 41%, 17%, 68%, 14%, and 511% respectively for Ge, Se, Mo, Te, and Nd, which indicates the importance of treating the triaxial deformation consistently in calculating the nuclear matrix elements.

    Comments:
    17 pages, 5 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2105.02649 [pdf]
    PRC(2021)·20 citations

Affiliations

first authorsco-authorsvia INSPIRE