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Nuclear Theory·nucl-th

Thursday·September 28, 2023

9 papers—5 primary·4 cross-listed

All9Primary5Cross-lists4
  1. 01

    [Submitted on 26 Sept 2023]

    Bounding the QCD Equation of State with the Lattice

    Guy D. Moore🇩🇪 · Tyler Gorda🇩🇪

    The equation of state of QCD matter at high densities is relevant for neutron star structure and for neutron star mergers and has been a focus of recent work. We show how lattice QCD simulations, free of sign problems, can provide an upper bound on the pressure as a function of quark chemical potentials. We show that at large chemical potentials this bound should become quite sharp; the difference between the upper bound on the pressure P-phase-quenched and the true pressure P is of order alpha^3 P. The corrections arise from a single Feynman diagram; its calculation would render remaining corrections of order alpha^4 P.

    Comments:
    11 pages including 2 figures, plus references. Minor corrections and more complete bibliography
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat)
    arXiv:
    2309.15149 [pdf]
    JHEP(2023)·25 citations
  2. 02

    [Submitted on 27 Sept 2023]

    In search of beyond mean-field signatures in heavy-ion fusion reactions

    R.T. deSouza · K. Godbey · S. Hudan · W. Nazarewicz

    Examination of high-resolution, experimental fusion excitation functions for O + C reveals a remarkable irregular behavior that is rooted in the structure of both the colliding nuclei and the quasi-molecular composite system. The impact of the -dependent fusion barriers is assessed using a time-dependent Hartree-Fock model. Barrier penetrabilities, taken directly from a density-constrained calculation, provide a significantly improved description of the experimental data as compared to the standard Hill-Wheeler approach. The remaining deviations between the parameter-free theoretical mean-field predictions and experimental fusion cross sections are exposed and discussed.

    Comments:
    Main manuscript, 6 pages, 4 figures; Supplemental material 2 videos and 1 figure
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2309.15327 [pdf]
    PRC(2024)·9 citations
  3. 03

    [Submitted on 27 Sept 2023]

    On partition temperature of massless particles in high-energy collisions

    Wei-Liang Qian🇨🇳 · Kai Lin🇨🇳 · Rui-Hong Yue🇨🇳 · Yogiro Hama🇧🇷 · Takeshi Kodama🇧🇷

    Although partition temperature derived using the Darwin-Fowler method is exact for simple scenarios, the derivation for complex systems might reside on specific approximations whose viability is not ensured if the thermodynamic limit is not attained. This work elaborates on a related problem relevant to relativistic high-energy collisions. On the one hand, it is simple enough that closed form expression can be obtained precisely for the one-particle distribution function. On the other hand, the resulting expression is not an exponential form, and therefore it is not straightforward that the notion of partition function could be implied. Specifically, we derive the one-particle distribution function for massless particles where the phase space integration is performed exactly for the underlying canonical ensemble consisting of a given number of particles. We discuss the viability of the partition temperature in this case. Possible implications of the obtained results regarding the observed Tsallis distribution in transverse momentum spectra in high-energy collisions are also addressed.

    Comments:
    12 pages, 2 figures, and 1 table
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2309.15356 [pdf]
    Symmetry(2023)·0 citations
  4. 04

    [Submitted on 27 Sept 2023]

    Finite-nuclear-size effect in hydrogen-like ions with relativistic nuclear structure

    Hui Hui Xie · Jian Li · Li Guang Jiao · Yew Kam Ho

    The finite-nuclear-size (FNS) effect has a large contribution to the atomic spectral properties especially for heavy nuclei. By adopting the microscopic nuclear charge density distributions obtained from the relativistic continuum Hartree-Bogoliubov (RCHB) theory, we systematically investigate the FNS corrections to atomic energy levels and bound-electron factors of hydrogen-like ions with nuclear charge up to . The comparison of the present numerical calculations with the predictions from empirical nuclear charge models, the non-relativistic Skyrme-Hartree-Fock calculations, and the results based on experimental charge densities indicate that both the nuclear charge radius and the detailed shape of charge density distribution play important roles in determining the FNS corrections. The variation of FNS corrections to energy levels and factors with respect to the nuclear charge are investigated for the lowest several bound states of hydrogen-like ions. It is shown that they both increase by orders of magnitude with increasing the nuclear charge, while the ratio between them has a relatively weak dependence on the nuclear charge. The FNS corrections to the and bound state energies from the RCHB calculations are generally in good agreement with the analytical estimations by Shabaev [J. Phys. B, 26, 1103 (1993)] based on the homogeneously charged sphere nuclear model, with the discrepancy indicating the distinct contribution of microscopic nuclear structure to the FNS effects.

    Comments:
    13 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
    arXiv:
    2309.15456 [pdf]
    PRA(2023)·13 citations
  5. 05

    [Submitted on 27 Sept 2023]

    Dynamical mechanism of fusion hindrance in heavy ion collisions

    S. Amano · Y. Aritomo · M. Ohta

    In the fusion process, the investigation of the reaction dynamics in the time evolution of the nuclear configuration is necessary. The neck parameter which is one of the parameters representing the nuclear configuration in the two center shell model is important in fusion owing to the nucleons transferring through the neck. The time evolution of the neck has not been discussed in detail, but is crucial for fusion cross section in the assessment of new elements synthesis. The dynamical analysis for the fusion hindrance under the neck formation on the nuclear deformation space has been done. The fusion probability considering the different denecking motion and the fusion hindrance are discussed. The calculations were performed using the dynamical model of nucleus-nucleus collisions based on the multidimensional Langevin equations.The formation of the neck bridge at the approaching stage is found to be crucial to the fusion hindrance. It is clarified that the inner barrier appears owing to the change in the degree of mass asymmetry with the relaxation of .The fusion hindrance occurs because the inner barrier is formed by the early neck formation. The role of the neck parameter is critically important for the fusion dynamics.

    Comments:
    9 pages, 9 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2309.15549 [pdf]
    PRC(2023)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE