Non-relativistic Mean Field Research Articles

Giant neutron halos in the non-relativistic mean field approach

Giant neutron halos in medium-heavy nuclei are studied in the framework of the Hartree-Fock-Bogoliubov (HFB) approach with Skyrme interactions. The appearance of such structures depends sensitively on the effective interaction adopted. This is illustrated by comparing the predictions of SLy4 and SkI4 in the Ca and Zr isotopic chains. The latter force predicts a neutron halo in the Zr chain with $A>122$ due to the weakly bound orbitals $3p1/2$ and $3p3/2$. It is found that the energies of states near the separation threshold depend sensitively on effective mass values. The structure of the halo is analyzed in terms of the occupation probabilities of these orbitals and their partial contributions to the neutron density. The antihalo effect is also discussed in the case of $^{124}\mathrm{Zr}$ by comparing the occupation probabilities and wave functions of the Hartree-Fock neutron single-particle states near the Fermi energy with the corresponding HFB quasiparticle states.

Sensitivity of neutron radii in aPb208nucleus and a neutron star to nucleon-σ-ρ coupling corrections in relativistic mean field theory

We study the sensitivity of the neutron skin thickness S in a Pb-208 nucleus to the addition of nucleon-sigma-rho coupling corrections to a selection (PK1, NL3, S271, and Z271) of interactions in a relativistic mean field model. The PK1 and NL3 effective interactions lead to a minimum value of S= 0.16 fm in comparison with the original value of S= 0.28 fm. The S271 and Z271 effective interactions yield even smaller values of S= 0.11 fm, which are similar to those for nonrelativistic mean field models. A precise measurement of the neutron radius, and therefore S, in Pb-208 will place an important constraint on both relativistic and nonrelativistic mean field models. We also study the correlation between the radius of a 1.4-solar-mass neutron star and S.

Nuclear shape transition at finite temperature in a relativistic mean field approach

The relativistic Hartree-BCS theory is applied to study the temperature dependence of nuclear shape and pairing gap for $^{166}Er$ and $^{170}Er$. For both the nuclei, we find that as temperature increases the pairing gap vanishes leading to phase transition from superfluid to normal phase as is observed in nonrelativistic calculation. The deformation evolves from prolate shapes to spherical shapes at $T\sim 2.7$ MeV. Comparison of our results for heat capacity with the ones obtained in the non-relativistic mean field framework indicates that in the relativistic mean field theory the shape transition occurs at a temperature about 0.9 MeV higher and is relatively weaker. The effect of thermal shape fluctuations on the temperature dependence of deformation is also studied. Relevant results for the level density parameter are further presented. PACS numbers: 21.10.Ma, 21.60.-n, 27.70.+q

Single-particle and collective motion for proton-rich nuclei in the upperpfshell

Based on available experimental data, a new set of Nilsson parameters is proposed for proton-rich nuclei with proton or neutron numbers $28<~N<~40.$ The resulting single-particle spectra are compared with those from relativistic and nonrelativistic mean field theories. Collective excitations in some even-even proton-rich nuclei in the upper $\mathrm{pf}$ 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.

Superdeformations in relativistic and non-relativistic mean field theories

The applications of the extensions of relativistic mean field (RMF) theory to the rotating frame, such as cranked relativistic mean field (CRMF) theory and cranked relativistic Hartree-Bogoliubov (CRHB) theory, for the description of superdeformed bands in the A ∼ 60, 140 – 150 and 190 mass regions are overviewed and compared briefly with the results obtained in non-relativistic mean field theories.

Incompressibility and density distributions in asymmetric nuclear systems

The incompressibility of asymmetric nuclear matter ${K}_{\ensuremath{\infty}}$ is studied analytically within the framework of the relativistic mean field theory and the nonrelativistic Skyrme Hartree-Fock model. We investigate also the relation between ${K}_{\ensuremath{\infty}}$ of asymmetric nuclear matter and the surface diffuseness by using the extended Thomas Fermi approximation. The self-consistent relativistic and nonrelativistic mean field calculations are performed for Sn isotopes, taking into account the pairing correlation, in order to extract the asymmetry parameter $(N$ $\ensuremath{-}Z)/A$ dependences of the surface diffuseness a and the central density $\ensuremath{\rho}(r=0).$ Clear correlations are found between the incompressibility ${K}_{\ensuremath{\infty}}$ of asymmetric nuclear matter and the extracted surface diffuseness $a,$ and also between ${K}_{\ensuremath{\infty}}$ and the extracted central density $\ensuremath{\rho}(r=0).$

Relativistic and Non-Relativistic Mean Field Investigation of the Superdeformed Bands in 62Zn

Following the first discovery of the superdeformed (SD) band in the A∼ 60 mass region, we calculate several low-lying SD bands in 62Zn using the relativistic mean field and Skyrme-Hartree-Fock models. Both models can reproduce the experimental moment of inertia very well, but we find that the calculated band, which corresponds to the experimentally observed band, does not become the lowest one. This trend is common among all the parameter sets which are widely used in RMF and SHF studies, and it seems to be connected with the fact that the position of the g9/2 level is not reproduced in 56Ni.

Semi-phenomenological neutron density distributions

The simple algebraic form for the nuclear densities designed to incorporate correctly, the two physical requirements, namely, the asymptotic behaviour and the behaviour near the centre, is used to calculate the neutron distributions in several nuclei. Sample neutron densities for 58,64 Ni, 116Sn and 208Pb are presented. The calculation reveals an excellent agreement with the experiment as well as with the relativistic and nonrelativistic microscopic mean field calculations. The use of this algebraic form of the densities in the analytic studies is strongly advocated.

Meissner effect in scalar QED with magnetic moment interactions.

We examine a model which describes the interactions of charged magnetic scalar particles with real gauge fields in 2+1 dimensions. At zero temperature and finite density, in the nonrelativistic mean field limit, the scalar fields have fractional statistics, and the theory contains the Meissner effect. In this limit, our model is effectively a reparametrization of the model that contains a Chern-Simons term for a statistical gauge field and couples the scalar field to the statistical gauge field and a real, dynamical gauge field. At high temperature, our model has a phase transition to the state where magnetic fields penetrate the system.