arXiv subjects

Jie Meng

Publications and source records attributed to Jie Meng.

154 records · Page 9Linked to original sources

arXiv2006

Evolution of Nuclear Shell Structure due to the Pion Exchange Potential

The evolution of nuclear shell structure is investigated for the first time within density-dependent relativistic Hartree-Fock theory and the role of $π$-exchange potential is studied in detail. The energy differences between the neutron orbits $\Lrb{\nu1h_{9/2},ν1i_{13/2}}$ in the N=82 isotones and between the proton ones $\Lrb{\pi1g_{7/2},\pi1h_{11/2}}$ in the Z=50 isotopes are extracted as a function of neutron excess $N-Z$. A kink around $Z = 58$ for the N=82 isotones is found as an effect resulting from pion correlations. It is shown that the inclusion of $π$-coupling plays a central role to provide realistic isospin dependence of the energy differences. In particular, the tensor part of the $π$-coupling has an important effect on the characteristic isospin dependence observed in recent experiments.

nucl-th↗

arXiv2006

Density-Dependent Relativistic Hartree-Fock Approach

A new relativistic Hartree-Fock approach with density-dependent $σ$, $ω$, $ρ$ and $π$ meson-nucleon couplings for finite nuclei and nuclear matter is presented. Good description for finite nuclei and nuclear matter is achieved with a number of adjustable parameters comparable to that of the relativistic mean field approach. With the Fock terms, the contribution of the $π$-meson is included and the description for the nucleon effective mass and its isospin and energy dependence is improved.

nucl-th↗

arXiv2006

Pseudo-spin symmetry in density-dependent relativistic Hartree-Fock theory

The pseudo-spin symmetry (PSS) is investigated in the density-dependent relativistic Hartree-Fock theory by taking {the} doubly magic nucleus $^{132}$Sn as a representative. It is found that the Fock terms bring significant contributions to the pseudo-spin orbital potentials (PSOP) and make it comparable to the pseudo-centrifugal barrier (PCB). However, these Fock terms in the PSOP are counteracted by other exchange terms due to the non-locality of the exchange potentials. The pseudo-spin orbital splitting indicates that the PSS is preserved well for the partner states $\lrb{ν3s_{1/2}, \nu2d_{3/2}}$ of $^{132}$Sn in the relativistic Hartree-Fock theory.

nucl-th↗

arXiv2005

Nuclear Symmetry Energy in Relativistic Mean Field Theory

The Physical origin of the nuclear symmetry energy is studied within the relativistic mean field (RMF) theory. Based on the nuclear binding energies calculated with and without mean isovector potential for several isobaric chains we conform earlier Skyrme-Hartree-Fock result that the nuclear symmetry energy strength depends on the mean level spacing $ε(A)$ and an effective mean isovector potential strength $κ(A)$. A detaied analysis of isospin dependence of the two components contributing to the nuclear symmetry energy reveals a quadratic dependence due to the mean-isoscalar potential, $\simεT^2$, and, completely unexpectedly, the presence of a strong linear component $\simκT(T+1+ε/κ)$ in the isovector potential. The latter generates a nuclear symmetry energy in RMF theory that is proportional to $E_{sym}\sim T(T+1)$ at variance to the non-relativistic calculation. The origin of the linear term in RMF theory needs to be further explored.

nucl-th↗

arXiv2005

Rotational damping in a multi-$j$ shell particles-rotor model

The damping of collective rotational motion is investigated by means of particles-rotor model in which the angular momentum coupling is treated exactly and the valence nucleons are in a multi-$j$ shell mean-field. It is found that the onset energy of rotational damping is around 1.1 MeV above yrast line, and the number of states which form rotational band structure is thus limited. The number of calculated rotational bands around 30 at a given angular momentum agrees qualitatively with experimental data. The onset of rotational damping takes place gradually as a function of excitation energy. It is shown that the pairing correlation between valence nucleons has a significant effect on the appearance of rotational damping.

nucl-th↗

arXiv2003

New effective interactions in RMF theory with non-linear terms and density-dependent meson-nucleon coupling

New parameter sets for the Lagrangian density in the relativistic mean field (RMF) theory, PK1 with nonlinear sigma- and omega-meson self-coupling, PK1R with nonlinear sigma-, omega- and rho-meson self-coupling and PKDD with the density-dependent meson-nucleon coupling, are proposed. They are able to provide an excellent description not only for the properties of nuclear matter but also for the nuclei in and far from the valley of beta-stability. For the first time in the parametrization of the RMF Lagrangian density, the center-of-mass correction is treated by a microscopic way, which is essential to unify the description of nuclei from light to heavy regions with one effective interaction.

nucl-th↗

arXiv2003

Spin symmetry in the anti-nucleon spectrum

We discuss spin and pseudo-spin symmetry in the spectrum of single nucleons and single anti-nucleons in a nucleus. As an example we use relativistic mean field theory to investigate single anti-nucleon spectra. We find a very well developed spin symmetry in single anti-neutron and single anti-proton spectra. The dominant components of the wave functions of the spin doublet are almost identical. This spin symmetry in anti-particle spectra and the pseudo-spin symmetry in particle spectra have the same origin. However it turns out that the spin symmetry in anti-nucleon spectra is much better developed than the pseudo-spin symmetry in normal nuclear single particle spectra.

nucl-th↗

arXiv2003

Spherical Relativistic Hartree theory in a Woods-Saxon basis

The Woods-Saxon basis has been suggested to replace the widely used harmonic oscillator basis for solving the relativistic mean field (RMF) theory in order to generalize it to study exotic nuclei. As examples, relativistic Hartree theory is solved for spherical nuclei in a Woods-Saxon basis obtained by solving either the Schrödinger equation or the Dirac equation (labelled as SRHSWS and SRHDWS, respectively and SRHWS for both). In SRHDWS, the negative levels in the Dirac Sea must be properly included. The basis in SRHDWS could be smaller than that in SRHSWS which will simplify the deformed problem. The results from SRHWS are compared in detail with those from solving the spherical relativistic Hartree theory in the harmonic oscillator basis (SRHHO) and those in the coordinate space (SRHR). All of these approaches give identical nuclear properties such as total binding energies and root mean square radii for stable nuclei. For exotic nuclei, e.g., $^{72}$Ca, SRHWS satisfactorily reproduces the neutron density distribution from SRHR, while SRHHO fails. It is shown that the Woods-Saxon basis can be extended to more complicated situations for exotic nuclei where both deformation and pairing have to be taken into account.

nucl-th↗

arXiv2000

Relativistic mean field description for the shears band mechanism in $^{84}$Rb

For the first time, the Relativistic Mean Field (RMF) model is applied to the shears band recently observed in $_{37}^{84}$Rb. Signals of the appearance of the shears mechanism, such as smooth decreases of the shears angle and of the $B$(M1)/$B$(E2) ratio with keeping the nearly constant tilt angle, are well reproduced. Thus it is shown that the microscopic RMF model can nicely describe the shears band in this nucleus.

nucl-th↗

arXiv2000

Single-Particle and Collective Motion for Proton-Rich Nuclei on the Astrophysical rp-Process Path

Based on available experimental data, a new set of Nilsson parameters is proposed for proton-rich nuclei with proton or neutron numbers $28\leq N\leq 40$. The resulting single-particle spectra are compared with those from relativistic and non-relativistic mean field theories. Collective excitations in some even--even proton-rich nuclei in the upper $pf$ shell are investigated using the Projected Shell Model with the new Nilsson basis. It is found that the regular bands are sharply disturbed by band crossings involving $1g_{9/2}$ neutrons and protons. Physical quantities for exploring the nature of the band disturbance and the role of the $1g_{9/2}$ single-particle are predicted, which may be tested by new experiments with radioactive beams.

nucl-th↗