Hartree-Fock (HF) calculations have had remarkable success in describing large nuclei athigh spin, temperature and deformation. To allow full range of possible deformations,the Skyrme HF equations can be discretized on a three-dimensional mesh. However, suchcalculations are currently limited by the computational resources provided by traditionalsupercomputers. To take advantage of recent developments in massively parallel computingtechnology, we have implemented the LLNL Skyrme-force static and rotationalHF codes on Intel's DELTA and GAMMA systems at Caltech.
We decomposed the HF code by assigning a portion of the mesh to each node, withnearest neighbor meshes assigned to nodes connected by communication· channels. Thiskind of decomposition is well-suited for the DELTA and the GAMMA architecture becausethe only non-local operations are wave function orthogonalization and the boundaryconditions of the Poisson equation for the Coulomb field.
Our first application of the HF code on parallel computers has been the study ofidentical superdeformed (SD) rotational bands in the Hg region. In the last ten years,many SD rotational bands have been found experimentally. One very surprising featurefound in these SD rotational bands is that many pairs of bands in nuclei that differby one or two mass units have nearly identical deexcitation gamma-ray energies. Ourcalculations of the five rotational bands in ^(192)Hg and ^(194)Pb show that the filling ofspecific orbitals can lead to bands with deexcitation gamma-ray energies differing by atmost 2 keV in nuclei differing by two mass units and over a range of angular momenta comparable to that observed experimentally. Our calculations of SD rotational bandsin the Dy region also show that twinning can be achieved by filling or emptying some specific orbitals.
The interpretation of future precise experiments on atomic parity nonconservation(PNC) in terms of parameters of the Standard Model could be hampered by uncertaintiesin the atomic and nuclear structure. As a further application of the massively parallelHF calculations, we calculated the proton and neutron densities of the Cesium isotopesfrom A = 125 to A = 139. Based on our good agreement with experimental chargeradii, binding energies, and ground state spins, we conclude that the uncertainties inthe ratios of weak charges are less than 10^(-3), comfortably smaller than the anticipated experimental error.
