Haozhao Liang

Hidden pseudospin and spin symmetries and their origins in atomic nuclei

Symmetry plays a fundamental role in physics. The quasi-degeneracy between single-particle orbitals

Spin-Isospin Resonances : A Self-Consistent Covariant Description

(n, l, j = l + 1/2)

Antimagnetic rotation band in nuclei: a microscopic description.

and

Isospin corrections for superallowed Fermi β decay in self-consistent relativistic random-phase approximation approaches

(n-1, l + 2, j = l + 3/2)

Novel structure for magnetic rotation bands in 60Ni

indicates a hidden symmetry in atomic nuclei, the so-called pseudospin symmetry (PSS). Since the introduction of the concept of PSS in atomic nuclei, there have been comprehensive efforts to understand its origin. Both splittings of spin doublets and pseudospin doublets play critical roles in the evolution of magic numbers in exotic nuclei discovered by modern spectroscopic studies with radioactive ion beam facilities. Since the PSS was recognized as a relativistic symmetry in 1990s, many special features, including the spin symmetry (SS) for anti-nucleon, and many new concepts have been introduced. In the present Review, we focus on the recent progress on the PSS and SS in various systems and potentials, including extensions of the PSS study from stable to exotic nuclei, from non-confining to confining potentials, from local to non-local potentials, from central to tensor potentials, from bound to resonant states, from nucleon to anti-nucleon spectra, from nucleon to hyperon spectra, and from spherical to deformed nuclei. Open issues in this field are also discussed in detail, including the perturbative nature, the supersymmetric representation with similarity renormalization group, and the puzzle of intruder states.

Perturbative interpretation of relativistic symmetries in nuclei

For the first time a fully self-consistent charge-exchange relativistic RPA based on the relativistic Hartree-Fock (RHF) approach is established. The self-consistency is verified by the so-called isobaric analog state (IAS) check. The excitation properties and the nonenergy weighted sum rules of two important charge-exchange excitation modes, the Gamow-Teller resonance (GTR) and the spin-dipole resonance (SDR), are well reproduced in the doubly magic nuclei 48Ca, 90Zr and 208Pb without readjustment of the particle-hole residual interaction. The dominant contribution of the exchange diagrams is demonstrated.

Pseudospin symmetry in supersymmetric quantum mechanics: Schrodinger equations

Covariant density functional theory and the tilted axis cranking method are used to investigate antimagnetic rotation (AMR) in nuclei for the first time in a fully self-consistent and microscopic way. The experimental spectrum as well as the B(E2) values of the recently observed AMR band in (105)Cd are reproduced very well. This gives a further strong hint that AMR is realized in specific bands in nuclei.

Spin symmetry in Dirac negative-energy spectrum in density-dependent relativistic Hartree-Fock theory

Self-consistent random phase approximation (RPA) approaches in the relativistic framework are applied to calculate the isospin symmetry-breaking corrections {delta}{sub c} for the 0{sup +}{yields}0{sup +} superallowed transitions. It is found that the corrections {delta}{sub c} are sensitive to the proper treatments of the Coulomb mean field, but not so much to specific effective interactions. With these corrections {delta}{sub c}, the nucleus-independent Ft values are obtained in combination with the experimental ft values in the most recent survey and the improved radiative corrections. It is found that the constancy of the Ft values is satisfied for all effective interactions employed. Furthermore, the element V{sub ud} and unitarity of the Cabibbo-Kobayashi-Maskawa matrix are discussed.

Mean-field study of single-particle spectra evolution in Z=14 and N=28 chains

Abstract The self-consistent tilted axis cranking relativistic mean-field theory based on a point-coupling interaction has been established and applied to investigate systematically the newly observed shears bands in 60 Ni. The tilted angles, deformation parameters, energy spectra, and reduced M1 and E2 transition probabilities have been studied in a fully microscopic and self-consistent way for various configurations and rotational frequencies. It is found the competition between the configurations and the transitions from the magnetic to the electric rotations have to be considered in order to reproduce the energy spectra as well as the band crossing phenomena. The tendency of the experimental electromagnetic transition ratios B ( M 1 ) / B ( E 2 ) is in a good agreement with the data, in particular, the B ( M 1 ) values decrease with increasing spin as expected for the shears mechanism, whose characteristics are discussed in detail by investigating the various contributions to the total angular momentum as well.

Localized form of Fock terms in nuclear covariant density functional theory

Perturbation theory is used systematically to investigate the symmetries of the Dirac Hamiltonian and their breaking in atomic nuclei. Using the perturbation corrections to the single-particle energies and wave functions, the link between the single-particle states in realistic nuclei and their counterparts in the symmetry limits is discussed. It is shown that the limit of S-V=const and relativistic harmonic oscillator (RHO) potentials can be connected to the actual Dirac Hamiltonian by the perturbation method, while the limit of S+V=const cannot, where S and V are the scalar and vector potentials, respectively. This indicates that the realistic system can be treated as a perturbation of spin-symmetric Hamiltonians, and the energy splitting of the pseudospin doublets can be regarded as a result of small perturbation around the Hamiltonian with RHO potentials, where the pseudospin doublets are quasidegenerate.