Setsuo Tamenaga

Chiral Sigma Model with Pion Mean Field in Finite Nuclei

The properties of infinite matter and finite nuclei are studied using the chiral sigma model in the framework of relativistic mean field theory. We reconstruct an extended chiral sigma model in which the omega meson mass is generated dynamically by sigma condensation in the vacuum in the same manner as the nucleon mass. All the parameters of the chiral sigma model are essentially fixed by the hadron properties in free space. In nuclear matter, the saturation property is described correctly, but the incompressibility is too large, and the scalar and vector potentials are about half as large as their phenomenological values. This fact is reflected in the properties of finite nuclei. We carry out calculations for N = Z eveneven mass nuclei between N = 16 and N = 34. The extended chiral sigma model without the pion mean field leads to the result that the magic number appears at N = 18, instead of N = 20, and the magic number does not appear at N = 28, due to the above mentioned nuclear matter properties. The latter problem, however, could be removed through the

Relativistic Chiral Mean Field Model for Finite Nuclei

We present a relativistic chiral mean field (RCMF) model, which is a method for the proper treatment of pion-exchange interaction in the nuclear many-body problem. There the dominant term of the pionic correlation is expressed in two-particle two-hole (2p-2h) states with particle-holes having pionic quantum number, J^{pi}. The charge-and-parity-projected relativistic mean field (CPPRMF) model developed so far treats surface properties of pionic correlation in 2p-2h states with J^{pi} = 0^{-} (spherical ansatz). We extend the CPPRMF model by taking 2p-2h states with higher spin quantum numbers, J^{pi} = 1^{+}, 2^{-}, 3^{+}, ... to describe the full strength of the pionic correlation in the intermediate range (r > 0.5 fm). We apply the RCMF model to the ^{4}He nucleus as a pilot calculation for the study of medium and heavy nuclei. We study the behavior of energy convergence with the pionic quantum number, J^{pi}, and find convergence around J^{pi}_{max} = 6^{-}. We include further the effect of the short-range repulsion in terms of the unitary correlation operator method (UCOM) for the central part of the pion-exchange interaction. The energy contribution of about 50% of the net two-body interaction comes from the tensor part and 20% comes from the spin-spin central part of the pion-exchange interaction.

Relativistic Hartree approach with exact treatment of vacuum polarization for finite nuclei

We study the relativistic Hartree approach with an exact treatment of the vacuum polarization in the Walecka

Self-consistent relativistic random-phase approximation with vacuum polarization

(\ensuremath{\sigma}\text{\ensuremath{-}}\ensuremath{\omega})

THE MASSLESS LINEAR SIGMA MODEL WITH LOOP CORRECTIONS

model. The contribution from the vacuum polarization of the nucleon-antinucleon field to the source term of the meson fields is evaluated by performing the energy integrals of the Dirac Green function along the imaginary axis. With the present method of calculating the vacuum polarization in finite system, the total binding energies and charge radii of

Relativistic Description of Semi-Infinite Nuclear Matter with Vacuum Polarization

^{16}\mathrm{O}

NUCLEAR GROUND STATES AND EXCITATIONS IN RELATIVISTIC NUCLEAR MODELS

and

THE ROLE OF PION ON NUCLEI WITH CHARGE AND PARITY PROJECTED CHIRAL MEAN FIELD MODEL

^{40}\mathrm{Ca}

CHIRAL SYMMETRY IN NUCLEAR MANY BODY SYSTEM

can be reproduced. On the other hand, the level splittings in the single-particle level, in particular the spin-orbit splittings, are not described well because the inclusion of vacuum effect provides a large effective mass with small meson fields. We also show that the derivative expansion of the effective action is fairly useful for the estimation of the vacuum effect.

Relativistic Chiral Mean Field Model with Projection for Finite Nuclei

We present a theoretical formulation for the description of nuclear excitations within the framework of a relativistic random-phase approximation whereby the vacuum polarization arising from nucleon-antinucleon fields is duly accounted for. The vacuum contribution to the Lagrangian is explicitly described as extra new terms of interacting mesons by means of the derivative expansion of the effective action. It is shown that the self-consistent calculation yields zero eigenvalue for the spurious isoscalar-dipole state and also conserves the vector-current density.