Exterior calculus on the computer: The REDUCE-package EXCALC applied to general relativity and to the Poincaré gauge theory

The computer algebra system REDUCE has recently been enriched by a package on exterior calculus. Here we apply the EXCALC package to the calculation of quantities within the Poincaré gauge theory of gravity, general relativity being included in this scheme as a spcial case. Thereby we simplify and streamline earlier results found by means of tensor-analytical REDUCE calculations.     

A semiquantal evaluation ofd 2 σ/dθ dE in DIC dynamically based on classical transport equations

The quantal double differential cross-section averaged over micro channels is parametrized in a way that accounts for the transfer of radial momentum and orbital angular momentum of relative motion of two colliding heavy ions into intrinsic degrees of freedom. The formfactors introduced are related to the solutions of classical Fokker-Planck equations and to semiclassical approximations of the phase shifts. An application of the model to⁴⁰Ar→²³²Th atE _lab=388 MeV which is based on familiar classical friction models and contains no further parameters yields a cross sectiond ² σ/dθ dE in good overall agreement with the experimental data.