Showing papers on "Schwinger variational principle published in 2006"

Elastic electron scattering by fullerene, C60

Abstract: We report cross sections for elastic scattering of low-energy electrons by fullerene, C60, calculated within the static-exchange approximation. The calculations are carried out via the Schwinger multichannel (SMC) method, equivalent in this case to the standard Schwinger variational principle. Combining the high parallel efficiency of the SMC method with a quadrature specially adapted to the high symmetry of C60 facilitates the most demanding step of the calculation and so permits the use of a large basis set. We analyze the structure of the cross section with reference to a simple spherical-shell model, and we compare our results to prior measurements and calculations.

Spinorial Field and Lyra Geometry

Abstract: The Dirac field is studied in a Lyra space-time background by means of the classical Schwinger Variational Principle. We obtain the equations of motion, establish the conservation laws, and get a scale relation relating the energy-momentum and spin tensors. Such scale relation is an intrinsic property for matter fields in Lyra background.

Variational approach to excitation of atomic hydrogen atoms by impacts of protons at intermediate velocities

Abstract: A variational approach to the excitation of atoms by ion impacts at intermediate velocities is re-examined. Contributions from intermediate states of the target continuum, that were ignored in previous applications of this approach, are taken into account. With this improved variational approach, excitation cross sections of hydrogen atoms by intermediate energy protons are calculated and compared to recent experimental data and to previous theoretical cross sections. The influence of the intermediate target continuum is found to be very weak. In addition, the present approach is shown to apply as long as the capture process is negligible.