acase@tulane.edu

acase@tulane.edu

acase@tulane.edu

acase@tulane.edu

acase@tulane.edu

acase@tulane.edu

acase@tulane.edu

This thesis work studies various nucleon-nucleon interaction models and their applications in two- and three-body calculations. Because direct solution of threebody Faddeev solutions reveals nearly unsurmountable calculational difficulties, EST method to generate a separable approximation to a given potential is examined with special care. Actual calculations are performed with EST approximations of the Paris and the Bonn potential, both of which are based on meson-exchange theories. The results manifest that meson-exchange picture is able to describe the nucleon-nucleon interaction for at least a wide energy range and that EST method is a simple and efficient way to construct a separable potential which carries both on-shell and off-shell informations of a given potential. Among other issues discussed in this thesis are some challenging problems in present three-nucleon physics, namely neutron analyzing power puzzle in neutron-deuteron scattering and triton binding energy gap between measured value and theoretical predictions. This work also investigates the possible existence of three-body force and its impacts on different observables and suggests the way to future progress in both two- and three-nucleon studies / acase@tulane.edu

acase@tulane.edu

The role of the nuclear orientation in the rotation of finite-temperature nuclei is investigated theoretically with microscopic nuclear structure models. An analytic formula is derived for the dynamic inertia tensor ${\cal J}\sp{(2)}$ of a hot rotating nucleus. This formula includes both mean field and pairing effects within the cranked finite-temperature Hartree-Fock-Bogoliubov (FTHFB) formalism. The intrinsic nuclear shape can have an arbitrary orientation relative to the rotation axis and the angular momentum can be large. Special case limits of this formula are presented and discussed. The rotation of hot triaxial nuclei is studied with the finite-temperature $i\sb{13/2}$ model. This model is used with three-dimensional cranking to calculate statistical fluctuations in the orientation of the intrinsic nuclear shape relative to the rotation axis. In the zero-temperature limit, the existence of 'tilted' yeast state solutions is demonstrated for even particle number. These solutions correspond to stable uniform rotation about an axis that lies in a principal plane of the nuclear potential. The possibility of stable tilting within the extended Landau theory of hot rotating nuclei is discussed. The FTHFB equation with three-dimensional cranking is solved to calculate statistical fluctuations in the orientation of $\sp{188}$Os relative to the nuclear spin vector. The principal axis frame is defined self-consistently for each orientation by constraining the quadrupole mass tensor to be diagonal. Orientation fluctuations are also computed with the macroscopic Landau theory of hot rotating nuclei, and the Landau results compare favorably with the microscopic FTHFB calculations. The possibility of stable tilted rotation is investigated for this nucleus. However, the nuclear free energy is found to be a minimum when the spin axis coincides with a principal axis of the quadrupole shape / acase@tulane.edu