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Nuclear Theory·nucl-th

Thursday·June 13, 2024

10 papers—4 primary·6 cross-listed

All10Primary4Cross-lists6
  1. 01

    Shear Viscosity of an -Component Gas Mixture using the Chapman--Enskog Method under Anisotropic Scatterings

    Noah M. MacKay

    The analytical Chapman-Enskog formula for calculating the shear viscosity of a relativistic ideal gas, such as a massless quark-gluon plasma, has consistently demonstrated good agreement with the numerical results obtained using the Green-Kubo relation under both isotropic and anisotropic two-body scatterings. However, past analyses of massless, multicomponent quark-gluon plasma have focused on an effective single-component "gluon gas." The Chapman-Enskog formula for multicomponent mixtures with nonzero yet adjustable masses was previously developed for simpler cases of isotropic scatterings. This study aims to obtain the Chapman-Enskog shear viscosity formula for a massless, multicomponent mixture under general anisotropic scatterings. Since the shear viscosity depends on a linearized collision kernel, an approximation formula for the linearized collision kernel is derived under elastic and anisotropic scatterings. This derived approximation agrees very well with the isotropic two-body kernels provided in previous works for both like and different species. Furthermore, for multicomponent mixtures beyond two species types, an alternative expansion method of the -component Chapman-Enskog viscosity is presented. This is applied to a two-component "binary" mixture and compared with the conventional formula for binary viscosity. The agreement between the two, for interacting and noninteracting binary mixtures, varies from moderate to well.

    nucl-thhep-th2 citations
  2. 02

    Ab initio calculations with a new local chiral N3LO nucleon-nucleon force

    P. Y. Wang · J. G. Li · S. Zhang · Q. Yuan · M. R. Xie · W. Zuo

    Ab initio calculations have achieved remarkable success in nuclear structure studies. Numerous works highlight the pivotal role of three-body forces in nuclear ab initio calculations. Concurrently, efforts have been made to replicate these calculations using only realistic nucleon-nucleon (NN) interactions. A novel local chiral next-to-next-to-next-to-leading order (N3LO) NN interaction, distinct due to its weaker tensor force, has recently been established. This paper applies this local NN interaction in ab initio frameworks to calculate the low-lying spectra of p-shell light nuclei, particularly 10B, ground-state energies and shell evolution in oxygen isotopes. Results are compared with calculations utilizing nonlocal chiral N3LO NN and chiral NN +3N interactions. The ab initio calculations with the local N N potential accurately describe the spectra of p-shell nuclei, notably the 10B. Additionally, the neutron drip line for oxygen isotopes, with 24O as the drip line nucleus, is accurately reproduced in ab initio calculations with the local NN interaction. Calculations with the local NN interaction also reproduce the subshell closure at N = 14 and 16, albeit with a stronger shell gap compared to experimental data. However, the calculated charge radii based on the local NN interaction are underestimated compared with experimental data, which is similar to results from the nonlocal NN interaction. Consequently, the present ab initio calculations further indicate significant spin-orbit splitting effects with the new local NN potential, suggesting that 3N forces remain an important consideration.

    nucl-thPRC(2024)·7 citations
  3. 03

    Towards a unified description of isotopic fragment properties in spontaneous and fusion-induced fission within a 4D dynamical Langevin model

    K. Pomorski🇵🇱 · B. Nerlo-Pomorska🇵🇱 · J. Bartel🇫🇷 · C. Schmitt🇫🇷 · Z. G. Xiao🇨🇳 · Y. J. Chen🇨🇳 · L. L. Liu🇨🇳

    Spontaneous fission of 252Cf and fusion-induced fission of 250Cf are investigated within a multi-dimensional Langevin model. The potential-energy surface is calculated in the macroscopic-microscopic LSD+Yukawa-folded approach using the four-dimensional Fourier-over-Spheroid shape parametrization. The dynamical evolution described by the Langevin equation is coupled to neutron evaporation, thereby allowing for the possibility of multi-chance fission. Charge equilibration and excitation-energy sharing between the fragments emerging at scission are evaluated, and their de-excitation is finally computed. The correlation between various observables, particularly the isotopic properties of the fragments, is discussed and compared with the experiment whenever available. The theoretical predictions are generally in good agreement with the data.

    nucl-thPRC(2024)·11 citations
  4. 04

    Unveiling potential neutron halos in intermediate-mass nuclei: an \textit{ab initio} study

    H. H. Li · J. G. Li · M. R. Xie · W. Zuo

    Halos epitomize the fascinating interplay between weak binding, shell evolution, and deformation effects, especially in nuclei near the drip line. In this Letter, we apply the state-of-the-art \textit{ab initio} valence-space in-medium similarity renormalization group approach to predict potential candidates for one- and two-neutron halo in the intermediate-mass region. Notably, we use spectroscopic factors (SF) and two-nucleon amplitudes (TNA) as criteria for suggesting one- and two-neutron halo candidates, respectively. This approach is not only theoretically sound but also amenable to experimental validation. Our research focuses on Mg, Al, Si, P, and S neutron-drip-line nuclei, offering systematic predictions of neutron halo candidates in terms of separation energies, SF (TNA), and average occupation. The calculation suggests the ground states of Al, Si, P, and S are promising candidates for one-neutron halos, while Mg, Al, Si, P, and S may harbor two-neutron halos. In addition, the relative mean-square neutron radius between halo nuclei and \textit{inner core} is calculated for suggested potential neutron halos. Finally, the relations of halo formations and shell evolution are discussed.

    nucl-thPRC(2024)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE