38852216
Pion optical potential with Delta dynamics.
A pion optical potential is constructed which incorporates the \ensuremath{\Delta} dynamics found to be important in \ensuremath{\Delta}-hole analyses of pion scattering from light nuclei. These dynamics include \ensuremath{\Delta} propagation, binding and Pauli blocking, and a \ensuremath{\Delta} spreading potential. We employ a local density approximation for the medium-modified \ensuremath{\Delta} propagator, resulting in a computationally flexible tool for the analysis of pion-nucleus data. We reproduce the \ensuremath{\Delta}-hole results for \ensuremath{\pi}${\mathrm{\ensuremath{-}}}^{16}$O scattering satisfactorily. Elastic ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$${\mathrm{\ensuremath{-}}}^{208}$Pb scattering is described very well with the same strongly damping spreading potential found for light nuclei. The pion wave functions in the medium are substantially modified by the \ensuremath{\Delta} dynamics.
44565255
Correlation effects in nuclear transparency.
The Glauber approximation is used to calculate the contribution of nucleon correlations in high-energy A(e,e'N) reactions. When the excitation energy of the residual nucleus is small, the increase of the nuclear transparency due to correlations between the struck nucleon and the other nucleons is mostly compensated by a decrease of the transparency due to the correlations between nondetected nucleons. We derive Glauber model predictions for nuclear transparency for the differential cross section when nuclear shell level excitations are measured. The role of correlations in color transparency is briefly discussed.
17521368
Quantization of the Bianchi type-IX model in supergravity with a cosmological constant.
Diagonal Bianchi type-IX models are studied in the quantum theory of $ N = 1 $ supergravity with a cosmological constant. It is shown, by imposing the supersymmetry and Lorentz quantum constraints, that there are no physical quantum states in this model. The $ k = + 1 $ Friedmann model in supergravity with cosmological constant does admit quantum states. However, the Bianchi type-IX model provides a better guide to the behaviour of a generic state, since more gravitino modes are available to be excited. These results indicate that there may be no physical quantum states in the full theory of $ N = 1 $ supergravity with a non-zero cosmological constant. are available to be excited. These results indicate that there may be no physical quantum states in the full theory of $ N = 1 $ supergravity with a non-zero cosmological constant.