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### Browsing by Author "Ring, Peter"

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- ItemEffects of tensor forces in nuclear spin–orbit splittings from ab initio calculations(Elsevier, 2018) Shen, Shihang; Liang, Haozhao; Meng, Jie; Ring, Peter; Zhang, Shuangquan
Show more A systematic and specific pattern due to the effects of the tensor forces is found in the evolution of spin–orbit splittings in neutron drops. This result is obtained from relativistic Brueckner–Hartree–Fock theory using the bare nucleon–nucleon interaction. It forms an important guide for future microscopic derivations of relativistic and nonrelativistic nuclear energy density functionals.Show more - ItemFully self-consistent relativistic Brueckner-Hartree-Fock theory for finite nuclei(American Physical Society, 2017) Shen, Shihang; Liang, Haozhao; Meng, Jie; Ring, Peter; Zhang, Shuangquan
Show more Starting from the relativistic form of the Bonn potential as a bare nucleon-nucleon interaction, the full relativistic Brueckner-Hartree-Fock (RBHF) equations are solved for finite nuclei in a fully self-consistent basis. This provides a relativistic ab initio calculation of the ground state properties of finite nuclei without any free parameters and without three-body forces. The convergence properties for the solutions of these coupled equations are discussed in detail for the example of the nucleus ¹⁶O. The binding energies, radii, and spin-orbit splittings of the doubly magic nuclei ⁴He, ¹⁶O, and ⁴⁰Ca are calculated and compared with the earlier RBHF calculated results in a fixed Dirac Woods-Saxon basis and other nonrelativistic ab initio calculated results based on pure two-body forces.Show more - ItemInfluence of pairing correlations on the radius of neutron-rich nuclei(American Physical Society, 2017) Zhang, Ying; Chen, Ying; Meng, Jie; Ring, Peter
Show more The influence of pairing correlations on the neutron root mean square (rms) radius of nuclei is investigated in the framework of self-consistent Skyrme Hartree-Fock-Bogoliubov calculations. The continuum is treated appropriately by the Green's function techniques. As an example the nucleus ¹²⁴Zr is treated for a varying strength of pairing correlations. We find that, as the pairing strength increases, the neutron rms radius first shrinks, reaches a minimum, and beyond this point it expands again. The shrinkage is due to the the so-called pairing antihalo effect, i.e., due to the decrease of the asymptotic density distribution with increasing pairing. However, in some cases, increasing pairing correlations can also lead to an expansion of the nucleus due to a growing occupation of so-called halo orbits, i.e., weakly bound states and resonances in the continuum with low-ℓ values. In this case, the neutron radii are extended just by the influence of pairing correlations, since these halo orbits cannot be occupied without pairing. The term “antihalo effect” is not justified in such cases. For a full understanding of this complicated interplay, self-consistent calculations are necessary.Show more - ItemRelativistic Brueckner-Hartree-Fock theory for neutron drops(American Physical Society, 2018) Shen, Shihang; Liang, Haozhao; Meng, Jie; Ring, Peter; Zhang, Shuangquan
Show more Neutron drops confined in an external field are studied in the framework of relativistic Brueckner-Hartree-Fock theory using the bare nucleon-nucleon interaction. The ground-state energies and radii of neutron drops with even numbers from N=4 to N=50 are calculated and compared with results obtained from other nonrelativistic ab initio calculations and from relativistic density functional theory. Special attention has been paid to the magic numbers and to the subshell closures. The single-particle energies are investigated and the monopole effect of the tensor force on the evolutions of the spin-orbit and the pseudospin-orbit splittings is discussed. The results provide interesting insights into neutron-rich systems and can form an important guide for future density functionals.Show more - ItemRelativistic Brueckner-Hartree-Fock theory in nuclear matter without the average momentum approximation(American Physical Society, 2018) Tong, Hui; Ren, Xiu-Lei; Ring, Peter; Shen, Shi-Hang; Wang, Si-Bo; Meng, Jie
Show more Brueckner-Hartree-Fock theory allows one to derive the G matrix as an effective interaction between nucleons in the nuclear medium. It depends on the center-of-mass momentum P of the two particles and on the two relative momenta q and q′ before and after the scattering process. In the evaluation of the total energy per particle in nuclear matter, usually the angle-averaged center-of-mass momentum approximation has been used. We derive in detail the exact expressions of the angular integrations of the momentum P within relativistic Brueckner-Hartree-Fock (RBHF) theory, especially for the case of asymmetric nuclear matter. In order to assess the reliability of the conventional average momentum approximation for the binding energy, the saturation properties of symmetric and asymmetric nuclear matter are systematically investigated based on the realistic Bonn nucleon-nucleon potential. It is found that the exact treatment of the center-of-mass momentum leads to non-negligible contributions to the higher order physical quantities. The correlations between the symmetry energy Esym, the slope parameter L, and the curvature Ksym of the symmetry energy are investigated. The results of our RBHF calculations for the bulk parameters characterizing the equation of state are compared with recent constraints extracted from giant monopole resonance and isospin diffusion experiments.Show more - ItemSpin symmetry in the Dirac sea derived from the bare nucleon–nucleon interaction(Elsevier, 2018) Shen, Shihang; Liang, Haozhao; Meng, Jie; Ring, Peter; Zhang, Shuangquan
Show more The spin symmetry in the Dirac sea has been investigated with relativistic Brueckner–Hartree–Fock theory using the bare nucleon–nucleon interaction. Taking the nucleus 16O as an example and comparing the theoretical results with the data, the definition of the single-particle potential in the Dirac sea is studied in detail. It is found that if the single-particle states in the Dirac sea are treated as occupied states, the ground state properties are in better agreement with experimental data. Moreover, in this case, the spin symmetry in the Dirac sea is better conserved and it is more consistent with the findings using phenomenological relativistic density functionals.Show more