Arbitrary Spacetimes from the SL(2,R)/U(1) Coset Model

We show that the gauged SL(2,R) WZWN model yields arbitrary spacetimes in two dimensions. The c = 1 matter field and the black hole singularity are just two particular cases in these spacetimes.Comment: 7 pages, latex file, BONN-HE-92-3

Field redefinition and renormalisability in scalar field theories

We have addressed the issue of field redefinition in connection with renormalisability. Our study is restricted to theories of interacting scalar fields. We have, in particular, shown that if a theory is renormalisable in the usual power-counting sense then it remains renormalisable in the same sense after a change of variables. This is due to the use of the powerful method of the background field expansion. In the case of a single complex sclar field, it turns out that the determination of the counter-terms is much simpler when polar coordinates are used. We illustate this by carrying out a one-loop calculation in the latter case.Comment: 13 pages, 2 figure

Classical duality in gauge theories

A dual action is obtained for a general non-abelian and non-supersymmetric gauge theory at the classical level. The construction follows steps similar to those used in pure abelian gauge theory. As an example we study the spontaneously broken SO(3) gauge theory and show that the electric and the magnetic fields get interchanged in the dual theory

Gauge invariance and non-constant gauge couplings

It is shown that space-time dependent gauge couplings do not completely break gauge invariance. We demonstrate this in various gauge theories.Comment: 18 page

Dynamical Evolution of the Extra Dimension in Brane Cosmology

The evolution of the extra dimension is investigated in the context of brane world cosmology. New cosmological solutions are found. In particular, solutions in the form of waves travelling along the extra dimension are identified.Comment: Latex file, 10 page