Time-independent mean field description of collisions

Products of single-particle orbitals are used as trial functions in a variational principle for the calculation of multistep nuclear collisions. The resulting dynamical equations are time-independent and generalize Hartree equations to nondiagonal mean fields with inhomogeneous source terms. These equations are solved for a $\text{p +}{}^3\text{H → p + n + d}$ breakup reaction.     

Two-fluid model description of isovector giant resonances in fast rotating nuclei

Isovector giant resonances of arbitrary multipolarity in fast rotating nuclei are studied by solving the inviscid two-fluid equation of relative motion in a rotating frame of reference. Both Coriolis and centrifugal forces are taken into account. The resulting expressions display in a quite simple way general features of giant multipole resonances of fast rotating nuclei, in addition to a good agreement with other calculations for the giant dipole resonance. Typical values for the resonance energies and their fragmentation due to nuclear deformation and rotation are given. In particular, enormously large resonance splitting should occur in the superdeformed states.     

On the isotopic dependence of the mean spin-orbit field in nuclei

An analysis has been made of experimental data on level spectra, single-nucleon transfer reactions near closed shells, and data on the polarization effects in charge-exchange (p, n) reactions between isoanalog states of nuclei with even A. The analysis has allowed us to conclude that there is a significant difference between the spin-orbit splittings of neutrons and protons in identical orbitals. This conclusion is confirmed in a framework of different theoretical approaches.     

Relativistic chiral mean field model for finite nuclei

We present a method for proper treatment of pion-exchange interaction in the nuclear many-body problem in a relativistic chiral mean field (RCMF) model. The pionic correlation is expressed in 2-particle 2-hole (2p–2h) states in addition to the standard mean field state, to describe the full strength of pionic correlations. The effect of the short-range repulsion is included by way of the unitary correlation operator method (UCOM) for the central part of the pion-exchange interaction. We apply the RCMF model to ¹²C and ¹⁶O. The convergence of pionic energy contributions is realized with pionic quantum number Jπ$J^{\pi }$ up to 10⁻ for ¹²C and 11⁺ for ¹⁶O. The pion-exchange interaction gives the dominant contribution to the binding energy. The pion plays an important role in the formation of the jj  -magic shell effect by way of the Pauli-blocking mechanism of the pion-exchange interaction. The lower pionic quantum numbers Jπ?³⁺$J^{\pi }?3^{+}$ are the dominant components of the nuclear surface structure.     

Nuclear magnetic moment: Relativistic mean field description

Valence nucleon effective mass, which is almost constant, is proposed within the relativistic mean field theories of finite nuclei (closed shell ± one nucleon). It acquires a slight spin-orbit splitting due to relativistic effects. The relativistic Dirac magnetic moment is rewritten analytically in terms of angular momentum-Pauli spin coupled states and the effective mass. Introducing the nucleon effective charge, the iso-scalar and iso-vector corrections to the magnetic moment operator are extracted from the overall one parameter fit of the measured and the calculated values. The calculated values of magnetic moments are in overall fair agreement with the experiment as well as with the other detailed microscopic calculations.     

Non-local mean field effect on nuclei near sub-shell

Evolutions of single-particle energies and Z=64 sub-shell along the isotonic chain of N=82 are investigated in the density dependent relativistic Hartree–Fock (DDRHF) theory in comparison with other commonly used mean field models such as Skyrme HF, Gogny HFB and density dependent relativistic Hartree model (DDRMF). The pairing is treated in the BCS scheme, except for Gogny HFB. It is pointed out that DDRHF reproduces well characteristic features of experimental Z-dependence of both spin–orbit and pseudo-spin–orbit splittings around the sub-shell closure Z=64. Non-local exchange terms of the isoscalar σ and ω couplings play dominant roles in the enhancements of the spin–orbit splitting of proton 2d states, which is the key ingredient to give the Z=64 sub-shell closure properly. On the other hand, the π and ρ tensor contributions for the spin–orbit splitting cancel each other and the net effect becomes rather small. The enhancement of the sub-shell gaps towards Z=64 is studied by the DDRHF, for which the local terms of the scalar and vector meson couplings are found to be important.     

Systematic study of bubble nuclei in relativistic mean field model

We have theoretically studied potential bubble nuclei (^20,22O, ^34,36Si, and ⁴⁶Ar), which are experimentally accessible and have attracted several studies in the recent past. Relativistic mean field is employed in conjunction with the NL–SH parameter set. Our results show that among the possible candidates, ²²Oand ³⁴Si may be the most prominent candidates, showing significant depletion of density at the center, which could be verified experimentally in the near future with some of the experiments underway.     

Cranked relativistic mean field description of superdeformed rotational bands

The cranked relativistic mean field theory is applied for a detailed investigation of eight superdeformed rotational bands observed in¹⁵¹Tb. It is shown that this theory is able to reproduce reasonably well not only the dynamic moments of inertiaJ ⁽²⁾ of the observed bands but also the alignment properties of the single-particle orbitals.     

Relativistic mean-field description of collective motion in nuclei: the pion field

The influence of the pion field on isovector dipole and spin-dipole collective oscillations is investigated in a time-dependent model based on relativistic mean field theory. We find that the inclusion of the long range pion-nucleon interaction provides an additional strong damping mechanism for the isovector dipole vibrations. The inclusion of the pion field has also a strong effect on the dynamics of spin-dipole vibrations, and in particular on the splitting of excitation energies of theJ ^π (0^?,1^?,2^?) components of the isovector spin-dipole resonance.     

Self-consistent field description of high spin states in rare earth nuclei

The Hartree-Fock-Begoliubov cranking equations are solved for ^{168, 170}Yb and ¹⁷⁴Hf. Deformation and pairing properties are both obtained with a G-matrix derived from the Reid soft-core potential. The high spin anomalies are attributed to the disappearance of the neutron pair gap in ¹⁶⁸Yb, the realignment of an $\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}$. neutron pair in ¹⁷⁰Yb, and a combination of these two mechanisms in ¹⁷⁴Hf. Two bands intersecting at high spin are found for ¹⁷⁴Hf.     

Self-consistent hartree description of finite nuclei in a relativistic quantum field theory

Relativistic Hartree equations for spherical nuclei are derived from a relativistic nuclear quantum field theory using a coordinate-space Green function approach. The renormalizable field theory lagrangian includes the interaction of nucleons with σ, ω, ρ and π mesons and the photon. The Hartree equations represent the “mean-field” approximation for a finite nuclear system. Coupling constants and the σ-meson mass are determined from the properties of nuclear matter and the rms charge radius in ⁴⁰Ca, and pionic contributions are absent for static, closed-shell nuclei. Calculated charge densities, neutron densities, rms radii, and single-nucleon energy levels throughout the periodic table are compared with data and with results of non-relativistic calculations. Relativistic Hartree results agree with experiment at a level comparable to that of the most sophisticated non-relativistic calculations to date. It is shown that the Lorentz covariance of the relativistic formalism leads naturally to density-dependent interactions between nucleons. Furthermore, non-relativistic reduction reveals non-central and non-local aspects inherent in the Hartree formalism. The success of this simple relativistic Hartree approach is attributed to these features of the interaction.     

Relativistic mean field approach to the scattering of antinucleons and nucleons by nuclei

A realistic mean field approach based on the Walecka theory for nuclear matter is used to derive the optical potential for nucleon and antinucleon-nucleus systems. The total and reaction cross sections are calculated in the WKB approximation for different nuclei ranging from carbon to lead and for incident energies between 0.1 and 2 GeV.     

Quantum correlations in rotating nuclei

Using the Hamiltonian that consists of the separable quadrupole + pairing forces and the cranking term, we analyze the correlations associated with shape, orientation, and particle-number fluctuations in rotating nuclei. Quantum fluctuations around mean field solutions are treated in the random phase approximation (RPA), with special emphasis on the restoration of rotational symmetry and particle number conservation. The mean field calculations have been made within the self-consistent cranking model. The effect of the RPA correlation energy for the moment of inertia is studied with the integral representation method proposed.     

Spin orientation in rotating nuclei

The orientation of the angular momentum in triaxial nuclei has been investigated in a three-dimensional cranked-HFB formalism. Some quasiparticle excitations are found to favour cranking about a non-principal axis for particular combinations of shell filling and triaxial shape. This effect also exists when the energy of the rotating core is added, at least for low spins, which is shown in a complete cranking calculation for ⁸⁴Y.     

IBM-2 description of M1 properties in deformed nuclei

Results of schematic calculations are presented in which various terms breaking F-spin symmetry are considered in the hamiltonian of the neutron-proton interacting boson model (IBM-2). Specific attention is paid to the effect of F-spin symmetry breaking on γ → ground and γ → γ M1 transitions in deformed nuclei. A comparison with available M1 data in the rare-earth nuclei is presented. The constraints implied by these data on the form of the IBM-2 hamiltonian in well-deformed nuclei are discussed.     

Multistable and excitable behavior in semiconductor ring lasers with broken Z<Subscript>2</Subscript>-symmetry

We study the bifurcation scenario and the evolution of the counter-propagating modes in a semiconductor ring laser when their symmetry is broken. We show how a two-dimensional asymptotic model for this asymmetric ring laser can be used to interpret and predict regions of multistability and excitability in the laser. The theoretical predictions and insights in these different dynamical regimes of the asymmetric semiconductor ring laser are confirmed and further explored experimentally in a semiconductor ring laser set-up that allows to controllably break the Z₂-symmetry of the laser.     

Candidate chiral nuclei in bromine isotopes based on triaxial relativistic mean field theory

Following the observation of candidate chiral doublet bands in ~(78,80)Br, triaxial deformations with corresponding configurations in odd-odd bromine isotopes have been investigated using adiabatic and configuration-fixed constrained triaxial relativistic-meanfield calculations with an aim of finding the boundary of chirality in the chain of Br isotopes. Several minima with triaxial deformation and the proper particle-hole configuration were obtained in ~(74,76,78,80,82)Br, where the chiral doublet bands have the possibility of occurrence. Furthermore, the possible existence of multiple chiral doublet(MχD) bands is demonstrated in ~(74,76,78,80,82)Br.Experiments to explore the chirality and MχD properties of Br isotopes are conducted to verify the predictions.     

On the quasiparticle description of nuclei

Zeitschrift für Physik A Hadrons and nuclei - TheT-operator of a stableN-nucleon system is expressed by means of a renormalizable equation. This equation is derived without any approximations...