Gauge principle and QED

One of the major developments of twentieth century physics has been the gradual recognition that a common feature of the known fundamental interactions is their gauge structure. In this talk the early history of gauge theory is reviewed, emphasizing especially Weyl's seminal contributions of 1918 and 1929.Comment: Invited talk at PHOTON2005, 31.8-04.09, 2005, Warsaw, 19 page

Proof of a decomposition theorem for symmetric tensors on spaces with constant curvature

In cosmological perturbation theory a first major step consists in the decomposition of the various perturbation amplitudes into scalar, vector and tensor perturbations, which mutually decouple. In performing this decomposition one uses -- beside the Hodge decomposition for one-forms -- an analogous decomposition of symmetric tensor fields of second rank on Riemannian manifolds with constant curvature. While the uniqueness of such a decomposition follows from Gauss' theorem, a rigorous existence proof is not obvious. In this note we establish this for smooth tensor fields, by making use of some important results for linear elliptic differential equations.Comment: 4 pages, accepted for publication in Annalen der Physi

The Membrane Model of Black Holes and Applications

These lectures provide a detailed introduction to the electro- dynamics of black holes. A simplified derivation of the basic membrane equations for stationary, axisymmetric black holes is given. The general theory is applied to idealized current generators involving rotating black holes, and we also analyse the Blandford-Znajek process for magnetic energy extraction from rotating black holes.Comment: 41 pages Latex document. 11 postscript figures available at ftp://130.60.164.117/pub/Straumann_Bad_Honnef/Straumann_Bad_Honnef_Bilder.tgz Lecture held at the 179. WE-Heraeus-Seminar, 18-22 of August 1997 at Bad Honnef (Germany). To be published in: Black Holes: Theory and Observation eds. F.W. Hehl, C. Kiefer and R. Metzler, Springer 199