Thetareihen und modulare Spitzenformen zu den Hilbertschen Modulgruppen reell-quadratischer Körper

Ohne Zusammenfassung     

Optical constants of 3,4,9,10-perylenetetracarboxylic dianhydride films on silicon and gallium arsenide studied by spectroscopic ellipsometry

The optical constants of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) films grown by organic molecular beam deposition on Si and GaAs substrates were determined in the spectral range from 300 nm to 1700 nm. All PTCDA layers deposited at room temperature with a low deposition rate of about 0.2 nm/min are uniaxial and strongly optically anisotropic. For the layers on Si a refractive index of 2.21 is derived in the substrate plane at 830 nm. The out-of-plane refractive index has a much lower value of 1.58. A similar anisotropy is observed for PTCDA layers on GaAs. The altogether lower refractive indices of 2.03 and 1.54, however, indicate a lower density of the films, which can be explained by the film structure. Received: 6 November 2000 / Accepted: 10 August 2001 / Published online: 17 October 2001     

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.