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Nuclear Theory·nucl-th

Tuesday·November 24, 2020

11 papers—4 primary·7 cross-listed

All11Primary4Cross-lists7
  1. 01

    [Submitted on 22 Nov 2020]

    QCD equations of state and speed of sound in neutron stars

    Toru Kojo🇨🇳

    Neutron stars are cosmic laboratories to study dense matter in Quantum Chromodynamics (QCD). The observable mass-radius relations of neutron stars are determined by QCD equations of state, and can reflect the properties of QCD phase transitions. In the last decade there have been historical discoveries in neutron stars, the discoveries of two-solar mass neutron stars and neutron star merger events, which have imposed tight constraints on equations of state. While a number of equations of state are constructed to satisfy these constraints, a theoretical challenge is how to reconcile those constructions with the microphysics expected from the hadron physics and in-medium calculations. In this short article we briefly go over recent observations and discuss their implications for dense QCD matter, referring to QCD constraints in the low and high density limits, QCD-like theories, and lattice QCD results for baryon-baryon interactions.

    Comments:
    9 pages, 2 figures, a review contributed to the AAPPS Bulletin; v2 published version
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2011.10940 [pdf]
    AAPPS Bull.(2021)·97 citations
  2. 02

    [Submitted on 22 Nov 2020]

    Ultraviolet suppression and nonlocality in optical model potentials for nucleon-nucleus scattering

    H. F. Arellano🇨🇱 · G. Blanchon🇫🇷

    We investigate the role of high momentum components of optical model potentials for nucleon-nucleus scattering and its incidence on their nonlocal structure in coordinate space. The study covers closed-shell nuclei with mass number in the range , for nucleon energies from tens of MeV up to 1 GeV. To this purpose microscopic optical potentials are calculated using density-dependent off-shell matrices in Brueckner-Hartree-Fock approximation and based on Argonne as well as chiral 2 force up to next-to-next-to-next-to-leading order. We confirm that the gradual suppression of high-momentum contributions of the optical potential results in quite different coordinate-space counterparts, all of them accounting for the same scattering observables. We infer a minimum cutoff momentum , function of the target mass number and energy of the process, that filters out irrelevant ultraviolet components of the potential. We find that when ultraviolet suppression is applied to Perey-Buck nonlocal potential or local Woods-Saxon potentials, they also result nonlocal with similar appearance to those obtained from microscopic models in momentum space. We examine the transversal nonlocality, quantity that makes comparable the intrinsic nonlocality of any potential regardless of its representation. We conclude that meaningful comparisons of nonlocal features of alternative potentials require the suppression of their ultraviolet components.

    Comments:
    12 pages, 15 figures. Accepted for publication in EPJA
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2011.11080 [pdf]
    EPJA(2021)·2 citations
  3. 03

    [Submitted on 23 Nov 2020]

    On the energy budget of the transition of a neutron star into the third family branch

    David E. Alvarez-Castillo🇵🇱

    Transition of a compact star into the third family for an equation of state (EoS) featuring mass twins is considered. The energy released at a baryon number conserving transition for static compact stars configurations is computed for two sets of models for comparison. The EoS of choice is the density dependent functional DD2 EoS with excluded model correction for hadronic matter which suffers a phase transition into deconfined quark matter described by a constant speed of sound approach. The two sets of EoS models feature different compact star mass onsets that maximize the energy and radius difference at the transition while simultaneously fulfilling state-of-the-art constraints from multi-messenger astronomy and empirical nuclear data. It is found that the maximal energy budget at the transitions falls in the range of - ergs.

    Comments:
    5 pages, 6 figures. Typos corrected, Figures 3 and 4 updated
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2011.11145 [pdf]
    Astron.Nachr.(2021)·10 citations
  4. 04

    [Submitted on 23 Nov 2020]

    Power counting in chiral effective field theory and nuclear binding

    C.-J. Yang🇸🇪 · A. Ekström🇸🇪 · C. Forssén🇸🇪 · G. Hagen🇺🇸

    Chiral effective field theory (EFT), as originally proposed by Weinberg, promises a theoretical connection between low-energy nuclear interactions and quantum chromodynamics (QCD). However, the important property of renormalization-group (RG) invariance is not fulfilled in current implementations and its consequences for predicting atomic nuclei beyond two- and three-nucleon systems has remained unknown. In this work we present a first and systematic study of recent RG-invariant formulations of EFT and their predictions for the binding energies and other observables of selected nuclear systems with mass-numbers up to . Specifically, we have carried out ab initio no-core shell-model and coupled cluster calculations of the ground-state energy of H, He, Li, and O using several recent power-counting (PC) schemes at leading order (LO) and next-to-leading order (NLO), where the subleading interactions are treated in perturbation theory. Our calculations indicate that RG-invariant and realistic predictions can be obtained for nuclei with mass number . We find, however, that O is either unbound with respect to the four -particle threshold, or deformed, or both. Similarly, we find that the Li ground-state resides above the -deuteron separation threshold. These results are in stark contrast with experimental data and point to either necessary fine-tuning of all relevant counterterms, or that current state-of-the-art RG-invariant PC schemes at LO in EFT lack necessary diagrams -- such as three-nucleon forces -- to realistically describe nuclei with mass number .

    Comments:
    18 pages, 12 figures, published version
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2011.11584 [pdf]
    PRC(2021)·47 citations

Affiliations

first authorsco-authorsvia INSPIRE