Dirac sea effects in K+K^+ scattering from nuclei

The ratio $R_T$ of $K^+-^{12}C$ to $K^+-d$ cross sections has been calculated microscopically using a boson-exchange $KN$ amplitude in which the $\sigma$ and $\omega$ mesons are dressed by the modifications of the Dirac sea in nuclear matter. In spite of the fact that this dressing leads to a scaling of the mesons effective mass in nuclear matter, the effect on the $R_T$ ratio is found to be weak.Comment: 8 pages, LaTeX, 2 figures available upon request, LPTB-93-

Gamow-Teller sum rule in relativistic nuclear models

Relativistic corrections are investigated to the Gamow-Teller(GT) sum rule with respect to the difference between the $\beta_-$ and $\beta_+$ transition strengths in nuclei. Since the sum rule requires the complete set of the nuclear states, the relativistic corrections come from the anti-nucleon degrees of freedom. In the relativistic mean field approximation, the total GT strengths carried by the nucleon sector is quenched by about 12% in nuclear matter, while by about 8% in finite nuclei, compared to the sum rule value. The coupling between the particle-hole states with the nucleon-antinucleon states is also discussed with the relativistic random phase approximation, where the divergence of the response function is renormalized with use of the counter terms in the Lagrangian. It is shown that the approximation to neglect the divergence, like the no-sea approximation extensively used so far, is unphysical, from the sum-rule point of view.Comment: 12 pages, Brief review for Mod. Phys. Lett. A, using ws-mpla.cl

Role of the Landau-Migdal Parameters with the Pseudovector and the Tensor Coupling in Relativistic Nuclear Models -- The Quenching of the Gamow-Teller Strength --

Role of the Landau-Migdal parameters with the pseudovector ($g_a$) and the tensor coupling ($g_t$) is examined for the giant Gamow-Teller (GT) states in the relativistic random phase approximation (RPA). The excitation energy is dominated by both $g_a$ and $g_t$ in a similar way, while the GT strength is independent of $g_a$ and $g_t$ in the RPA of the nucleon space, and is quenched, compared with that in non-relativistic one. The coupling of the particle-hole states with nucleon-antinucleon states is expected to quench the GT strength further through $g_a$.Comment: 7 pages, ReVTe

The Gamow-Teller States in Relativistic Nuclear Models

The Gamow-Teller(GT) states are investigated in relativistic models. The Landau-Migdal(LM) parameter is introduced in the Lagrangian as a contact term with the pseudo-vector coupling. In the relativistic model the total GT strength in the nucleon space is quenched by about 12% in nuclear matter and by about 6% in finite nuclei, compared with the one of the Ikeda-Fujii-Fujita sum rule. The quenched amount is taken by nucleon-antinucleon excitations in the time-like region. Because of the quenching, the relativistic model requires a larger value of the LM parameter than non-relativistic models in describing the excitation energy of the GT state. The Pauli blocking terms are not important for the description of the GT states.Comment: REVTeX4, no figure

Sum Rules of the Multiple Giant Dipole States

Various sum rules for multiple giant dipole resonance states are derived. For the triple giant dipole resonance states, the energy-weighted sum of the transition strengths requires a model to be related to those of the single and double giant dipole resonance states. It is also shown that the non-diagonal matrix elements of the double commutator between the dipole operator and the nuclear Hamiltonian give useful identities for the excitation energy and transition strength of each excited state. Using those identities, the relationship between width of the single dipole state and those of the multiple ones is qualitatively discussed.Comment: 8 pages, 1 figure, using PTPTeX styl

Optimal” Inflation Under Dollarization

This paper analyzes the effects of dollarization, where a country (C) uses money produced by another country (M). We derive a general formula to determine the optimal rate of inflation, which maximizes M\u27s welfare but does not take into account any loss to C. We show how this inflation varies with relative income size and output growth. Estimates of the optimal inflation rate are made for some countries. We also analyze a contract, under which M shares a fraction of total potential seignorage with C to induce M to inflate at a rate which leads to no seigniorage accruing to M from C. Finally, we provide estimates of the present discounted value of the seigniorage accruing from M to C. Despite this loss, we estimate the net welfare gain to C\u27s household when dollarization results in a lower rate of inflation