arXiv subjects

Yataro Horikawa

Publications and source records attributed to Yataro Horikawa.

3 recordsLinked to original sources

arXiv2004

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

We study the relativistic Hartree approach with the exact treatment of the vacuum polarization in the Walecka sigma-omega model. The contribution from the vacuum polarization of 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 the vacuum polarization in finite system, the total binding energies and charge radii of 16O and 40Ca can be reproduced. On the other hand, the level-splittings in the single-particle level, in particular the spin-orbit splittings, are not described nicely 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 which has been used to calculate the vacuum contribution for finite nuclei gives a fairly good approximation.

nucl-th↗

arXiv2002

Gauge Invariant Evaluation of Nuclear Polarization with Collective Model

The nuclear-polarization (NP) energies with the collective model commonly employed in the NP calculations for hydrogenlike heavy ions are found to have serious gauge violations when the ladder and cross diagrams only are taken into account. Using the equivalence of charge-current density with a schematic microscopic model, the NP energy shifts with the collective model are gauge invariantly evaluated for the $1s_{1/2}$ states in $^{208}_{~82}$Pb$^{81+}$ and $^{238}_{~92}$U$^{91+}$.

physics.atom-ph↗

arXiv2001

Nuclear polarization in hydrogenlike $^{208}_{~82}$Pb$^{81+}$

We calculate nuclear-polarization energy shifts for hydrogenlike $^{208}_{~82}$Pb$^{81+}$. A retarded transverse part as well as the Coulomb part is taken into account as the electromagnetic interaction between an electron and the nucleus. With a finite charge distribution for the nuclear ground state and the random-phase approximation to describe the nuclear excitations, we obtain nuclear polarization energy of the $1s_{1/2}$ state as --38.2 (--37.0) meV in the Feynman (Coulomb) gauge. For the $2s_{1/2}$, $2p_{1/2}$ and $2p_{3/2}$ states, they are --6.7 (--6.4), --0.2 (--0.2) and +0.0 (+0.0) meV, respectively. The seagull term in the two-photon exchange diagrams is shown to be quite important to obtain the gauge invariance of the nuclear polarization energies.

nucl-th↗