Hyperon coupling dependence of hadron matter properties in relativistic mean field model

The properties of hadronic matter at beta equilibrium in a wide range of densities are described by appropriate equations of state in the framework of the relativistic mean field model. Strange meson fields, namely the scalar meson field sigma*(975) and the vector meson field sigma*(1020), are included in the present work. We discuss and compare the results of the equation of state, nucleon effective mass, and strangeness fraction obtained by adopting the TM1, TMA, and GL parameter sets for nuclear sector and three different choices for the hyperon couplings. We find that the parameter set TM1 favours the onset of hyperons most, while at high densities the GL parameter set leads to the most hyperon-rich matter. For a certain parameter set (e.g. TM1), the most hyperon-rich matter is obtained for the hyperon potential model. The influence of the hyperon couplings on the effective mass of nucleon, is much weaker than that on the nucleon parameter set. The nonstrange mesons dominate essentially the global properties of dense hyperon matter. The hyperon potential model predicts the lowest value of the neutron star maximum mass of about 1.45 M-sun to be 0.4-0.5 M-sun lower than the prediction by using the other choices for hyperon couplings.

Hyperon-hyperon interaction in relativistic mean field model

By using the new experimental data of Lambda Lambda potential, this paper has performed a full calculation for strange hadronic matter with different strangeness contents as well as its consequences on the global properties of neutron star matter in relativistic mean field model. It finds that the new weak hyperon - hyperon interaction makes the equations of state much stiffer than the result of the previous strong hyperon-hyperon interaction, and even stiffer than the result without consideration of hyperon -hyperon interaction. This new hyperon -hyperon interaction results in a maximum mass of 1.75M(circle dot) ( where M-circle dot stands for the mass of the Sun), about 0.2-0.5M(circle dot) larger than the previous prediction with the presence of hyperons. After examining carefully the onset densities of kaon condensation it finds that this new weak version of hyperon -hyperon interaction favours the occurrence of kaons in comparison with the strong one.

Improved BCS-type pairing for the relativistic mean-field theory

A density-dependent delta interaction (DDDI) is proposed in the formalism of BCS-type pairing correlations for exotic nuclei whose Fermi surfaces are close to the threshold of the unbound state. It provides the possibility to pick up those states whose wave functions are concentrated in the nuclear region by making the pairing matrix elements state dependent. On this basis, the energy level distributions, occupations, and ground-state properties are self-consistently studied in the RMF theory with deformation. Calculations are performed for the Sr isotopic chain. A good description of the total energy per nucleon, deformations, two-neutron separation energies and isotope shift from the proton drip line to the neutron drip line is found. Especially, by comparing the single-particle structure from the DDDI pairing interaction with that from the constant pairing interaction for a very neutron-rich nucleus it is demonstrated that the DDDI pairing method improves the treatment of the pairing in the continuum.

Pb isotope shifts in the relativistic mean field theory

The ground state properties of the Pb isotopic are studied by using the axially deformed relativistic mean field (RMF) calculation with the parameter set TM1. The pairing correlation is treated by the BCS method and the isospin dependent pairing force is used. The 'blocking' method is used to deal with unpaired nucleons. The theoretical results show that the relativistic mean field theory with non-linear self-interactions of mesons provides a good description of the binding energy and neutron separation energy. The present paper focus on the physical mechanism of the Pb isotope shifts.

Properties and structure of N = Z nuclei within relativistic mean field theory

The axially deformed relativistic mean field theory with the force NLSH has been performed in the blocked BCS approximation to investigate the proper-ties and structure of N=Z nuclei from Z=20 to Z=48. Some ground state quantities such as binding energies, quadrupole deformations, one/two-nucleon separation energies, root-mean-squaxe (rms) radii of charge and neutron, and shell gaps have been calculated. The results suggest that large deformations can be found in medium-heavy nuclei with N=Z=38-42. The charge and neutron rms radii increase rapidly beyond the magic number N=Z=28 until Z=42 with increasing nucleon number, which is similar to isotope shift, yet beyond Z=42, they decrease dramatically as the structure changes greatly from Z=42 to Z=43. The evolution of shell gaps with proton number Z can be clearly observed. Besides the appearance of possible new shell closures, some conventional shell closures have been found to disappear in some region. In addition, we found that the Coulomb interaction is not strong enough to breakdown the shell structure of protons in the current region.

Relativistic Mean Field Study of the Z=117 Isotopic Chain

The properties of the Z = 117 isotopic chain are studied within the framework of the axially deformed relativistic mean field theory (RMFT) in the blocked BCS approximation. The ground-state properties, such as binging energies, deformations as well as the possible.. decay energies and lifetimes are calculated with the parameter set of NL-Z2 and compared with results from the finite range droplet model. The analysis by RMFT shows that the isotopes in the range of mass number A = 291 similar to 300 exhibit higher stability, which suggests that they may be promising nuclei to be hopefully synthesized in the lab among the nuclei Z = 117.

Mean-field study of Fe2+- and Co2+-doped diluted magnetic semiconductors

Based on a modified mean-field model, we calculate the Curie temperatures of Fe2+- and Co2+-doped diluted magnetic semiconductors (DMSs) and their dependence on the hole concentration. We find that the Curie temperatures increase with an increase in hole concentration and the relationship T(C)proportional to p(1/3) also approximately holds for Fe2+- and Co2+-doped systems with moderate hole concentration. For either low or high hole concentrations, however, the p(1/3) law is violated due to the anomalous magnetization of the Fe2+ and Co2+ ions, and the nonparabolic nature of the hole bands. Further, the values of T-C for Fe2+- and Co2+-doped DMSs are significantly higher than those for Mn2+-doped DMSs, due to the larger exchange interaction strength.

Electronic structure of Mn-doped ZnO quantum wires: A mean-field theory study

Based on the effective-mass model and the mean-field approximation, we investigate the energy levels of the electron and hole states of the Mn-doped ZnO quantum wires (x=0.0018) in the presence of the external magnetic field. It is found that either twofold degenerated electron or fourfold degenerated hole states split in the field. The splitting energy is about 100 times larger than those of undoped cases. There is a dark exciton effect when the radius R is smaller than 16.6 nm, and it is independent of the effective doped Mn concentration. The lowest state transitions split into six Zeeman components in the magnetic field, four sigma(+/-) and two pi polarized Zeeman components, their splittings depend on the Mn-doped concentration, and the order of pi and sigma(+/-) polarized Zeeman components is reversed for thin quantum wires (R < 2.3 nm) due to the quantum confinement effect.