7508491
Effect of isospin mixing on superallowed Fermi beta decay.
We study the effect of isospin impurity on the superallowed Fermi {beta} decay using the microscopic Hartree-Fock and random phase approximation (or Tamm-Dancoff approximation) model taking into account charge symmetry and independence breaking interactions. It is found that the isospin impurity of {ital N}={ital Z} nuclei gives enhancement of the sum rule of Fermi transition probabilities. On the other hand, the superallowed transitions between odd-odd {ital J}=0 nuclei and even-even {ital J}=0 nuclei are quenched because of the cancellation of the isospin impurity effects of mother and daughter nuclei. An implication of the calculated Fermi transition rate on the unitarity of the Cabibbo-Kobayashi-Maskawa mixing matrix is also discussed. {copyright} {ital 1996 The American Physical Society.}
121477777
Double giant resonance states
The strength, excitation energy and width of the double giant dipole and quadrupole resonances are studied. The model-independent sum rules for the strength are derived. It is shown that the folding model satisfies the sum rule, but can not reproduce experimental data. The energy and width of the double giant dipole resonance can be expressed rather model-independently in terms of those of the single giant dipole resonance. Their relationship is in good agreement with experiment.
120525345
DAMPING WIDTH OF THE MIE PLASMON
1660325
Effects of the Dirac sea on the giant monopole states
Abstract Effects of the Dirac sea on the excitation energy of the giant monopole states are investigated in an analytic way within the σ − ω model. The excitation energy is determined by the relativistic Landau-Migdal parameters, F 0 and F 1 . Their analytic expressions are derived in the relativistic random phase approximation (RRPA) without the Dirac sea, with the Pauli blocking terms and with the full Dirac sea. It is shown that in the RRPA based on the mean field approximation the Pauli blocking terms should be included in the configuration space, according to the relativistic Landau theory. In the renormalized RRPA, the incompressibility coefficient becomes negative, if NN excitations are neglected.
121914219
The Continuity Equation of RPA
The Hartree-Fock approximation violates the continuity equation of the nuclear four­ current. It is shown that the random phase approximation restores the equation approx­ imately. The RPA theorem on the sum rule is derived from the approximate continuity equation. The nuclear four-current should satisfy the continuity equation. In particular, the continuity equation plays an essential role in the study of nuclear response to electromagnetic fields. The Siegert theorem for photo reactions relies on this equa­ tion. In electron scattering, longitudinal and transverse form factors are related to each other through the continuity equation. Generally speaking, this equation is as­ sured by the gauge invariance. In many-body calculations, however, it is not trivial that matrix elements of the density and current satisfy the continuity equation, since the Schrodinger equation is not satisfied exactly. The purpose of the present paper is to show that in the random phase approximation (RPA) based on the Hartree-Fock approximation (HFA), the continuity equation is satisfied approximately, The RPA theOrem with regard to the energy-weighted sum rule of Thouless 1) is obtained from the approximate continuity equation. Before considering RPA, it is instructive to show how the HFA violates the conti­ nuity equation. We discuss in detail the isoscalar density, which is in the momentum space given by A
8239852
Exotic Structure of Carbon Isotopes
We studied firstly the ground state properties of C-isotopes using a deformed Hartree-Fock (HF)+ BCS model with Skyrme interactions. Shallow deformation minima are found in several neutron$-$rich C-isotopes. It is shown also that the deformation minima appear in both the oblate and the prolate sides in $^{17}$C and $^{19}$C having almost the same binding energies. Secondly, we carried out shell model calculations to study electromagnetic moments and electric dipole transitions of the C-isotopes. We point out the clear configuration dependence of the quadrupole and magnetic moments in the odd C-isotopes, which will be useful to find out the deformations and the spin-parities of the ground states of these nuclei. We studied electric dipole states of C-isotopes focusing on the interplay between low energy Pigmy strength and giant dipole resonances. 
Reasonable agreement is obtained with available experimental data for the photoreaction cross sections both in the low energy region below $\hbar \omega $=14 MeV and in the high energy giant resonance region (14 MeV $<\hbar \omega \leq $30 MeV). 
The calculated transition strength below dipole giant resonance ($\hbar \omega \leq $14 MeV) in heavier C-isotopes than $^{15}$C is found to exhaust about $12\sim16%$ of the classical Thomas-Reiche-Kuhn sum rule value and $50\sim80%$ of the cluster sum rule value.
39484293
Flat directions in de Sitter space.
The one loop level effective potential along the flat direction in global supersymmetric models is evaluated in de Sitter space. In flat space the direction \ensuremath{\varphi} only has a curvature determined by the supersymmetry soft breaking mass term ${\mathit{m}}^{2}$${\mathrm{\ensuremath{\varphi}}}^{2}$ and in the supersymmetric limit m\ensuremath{\rightarrow}0 it receives no radiative corrections because of the nonrenormalization theorem. In this paper we show that in de Sitter space the one loop radiative correction induces a term \ensuremath{\sim}-3${\mathit{g}}^{2}$${\mathit{H}}^{2}$${\mathrm{\ensuremath{\varphi}}}^{2}$ ln(${\mathrm{\ensuremath{\varphi}}}^{2}$)/(16${\mathrm{\ensuremath{\pi}}}^{2}$) on the flat direction, where g is a typical coupling constant and H is the Hubble parameter. If the (renormalized) curvature coupling is nearly zero, \ensuremath{\xi}\ensuremath{\simeq}0, and the soft breaking mass is sufficiently small as ${\mathit{m}}^{2}$\ensuremath{\lesssim}${\mathit{g}}^{2}$${\mathit{H}}^{2}$/${\mathrm{\ensuremath{\pi}}}^{2}$, the correction may qualitatively modify the tree level potential and give an unbounded potential for the flat direction. We argue that this behavior is irrespective of the matter content and the details of the model if the flat direction couples to a scalar multiplet (as realistic supersymmetric models should do). The unbounded potential may give a large vacuum expectation value of \ensuremath{\varphi} in the inflationary expanding universe and be desirable for baryogenesis by the Affleck-Dine mechanism. Including the back reaction effect, the unbounded potential may also cause the adjustment mechanism for the cosmological constant problem.
38379322
Quantum tunneling with dissipation: Possible enhancement by dissipative interactions.
The macroscopic quantum tunneling in a double-well potential with dissipation is formulated without referring to instantons. This formulation, in the domain of small dissipation, goes beyond the instanton approximation which corresponds to the two-state truncated system (or, the so-called spin-boson Hamiltonian). It is first confirmed that our formulation, when applied to the two-state truncated system, reproduces all the known results of the instanton approximation. It is then shown that the ground state is mixed with excited states by dissipative interactions and this effect tends to enhance the ground-state quantum tunneling. In the Ohmic dissipation case this enhancement factor, even for a shallow double-well potential, can be at most comparable to the suppression factor which has been known from the work by Caldeira and Leggett. In the super-Ohmic case, however, the enhancement factor generally exceeds the suppression factor and the two-state approximation fails. A salient feature in the choice of counter terms in macroscopic quantum tunneling, which is essential to the above conclusion, is emphasized.