Deformations of WZW models

Current-current deformations for WZW models of semisimple compact groups are discussed in a sigma model approach. We start with the abelian rank one group U(1). Afterwards, we keep the rank one but allow for non abelian structures by considering SU(2). Finally, we present the general case of rank larger than one.Comment: 8 pages, contribution to the proceedings of the 36th International Symposium Ahrenshoop, Berlin, August 26-30, 2003, and of the RTN Workshop in Copenhagen, September 15-20, 2003, references adde

A Small Cosmological Constant and Backreaction of Non-Finetuned Parameters

We include the backreaction on the warped geometry induced by non-finetuned parameters in a two domain-wall set-up to obtain an exponentially small Cosmological Constant $\Lambda_4$. The mechanism to suppress the Cosmological Constant involves one classical fine-tuning as compared to an infinity of finetunings at the quantum level in standard D=4 field theory.Comment: 13 pages, minor corrections and references adde

New brane solutions in higher order gravity

We consider the higher order gravity with dilaton and with the leading string theory corrections taken into account. The domain wall type solutions are investigated for arbitrary number of space-time dimensions. The explicit formulae for the fixed points and asymptotic behavior of generic solutions are given. We analyze and classify solutions with finite effective gravitational constant. There is a class of such solutions which have no singularities. We discuss in detail the relation between fine tuning and self tuning and clarify in which sense our solutions are fine-tuning free. The stability of such solutions is also discussed.Comment: 22 pages, Latex, 3 figures; discussion of effective gravitational constant and of one type of solutions extended; references adde

Heterotic orbifold models on Lie lattice with discrete torsion

We provide a new class of Z_N x Z_M heterotic orbifolds on non-factorisable tori, whose boundary conditions are defined by Lie lattices. Generally, point groups of these orbifolds are generated by Weyl reflections and outer automorphisms of the lattices. We classify abelian orbifolds with and without discrete torsion. Then we find that some of these models have smaller Euler numbers than those of models on factorisable tori T^2 x T^2 x T^2. There is a possibility that these orbifolds provide smaller generation numbers of N=1 chiral matter fields than factorisable models.Comment: 24 pages, 5 figures; v2: a few errors on tables are corrected, typos corrected, version to appear in JHE

Transparency in Local Government A Case Study of Transparency in Hamburg and Antwerp: Giving People What They Need?

This paper examines through what means local government can realize transparency policies and to what extent real transparency is achieved. We conduct a comparative study of information policies in Hamburg and Antwerp. In these studies we compare how both cities score on building real transparency in implementing laws aimed at increasing transparency. We define six indicators of real transparency in section 2 Indicators of Real Transparency. The aim of this paper is to show that there can be limits to the transparency effect of information distribution in terms of what is necessary, useful and understandable information transmitted to the public. Ill-considered implementation of right of information and transparency policies is not sufficient. We claim that, the subjective quality of the information, in terms of accessibility but also understandability is of overriding importance

Deformations and Geometric Cosets

I review some marginal deformations of SU(2) and SL(2,R) Wess-Zumino-Witten models, which are relevant for the investigation of the moduli space of NS5/F1 brane configurations. Particular emphasis is given to the asymmetric deformations, triggered by electric or magnetic fluxes. These exhibit critical values, where the target spaces become exact geometric cosets such as S2 = SU(2)/U(1) or AdS2 = SL(2,R)/U(1)-space. I comment about further generalizations towards the appearance of flag spaces as exact string solutions.Comment: 10 page

D-branes on a Deformation of SU(2)

We discuss D-branes on a line of conformal field theories connected by an exact marginal deformation. The line contains an SU(2) WZW model and two mutually T-dual SU(2)/U(1) cosets times a free boson. We find the D-branes preserving a U(1) isometry, an F-flux quantization condition and conformal invariance. Away from the SU(2) point a U(1) times U(1) symmetry is broken to U(1) times Z_k, i.e. continuous rotations of branes are accompanied by rotations along the branes. Requiring decoupling of the cosets from the free boson at the endpoints of the deformation breaks the continuous rotation of branes to Z_k. At the SU(2) point the full U(1) times U(1) symmetry is restored. This suggests the occurrence of phase transitions for branes at angles in the coset model, at a semiclassical level. We also discuss briefly the orientifold planes along the deformation line.Comment: 19 pages, latex, 5 figures, references adde

Strings from Orientifolds

We construct models in 1+1 dimensions with chiral (0,N) supersymmetry by taking orientifolds of type IIB on an eight-torus identified by different numbers of reflections. The resulting models have Dirichlet strings, fivebranes and ninebranes stretched along different directions. The cases we study in detail have residual chiral supersymmetry (0,8), (0,4) and (0,2). The gravitational anomaly in all cases is shown to cancel.Comment: 30 pages, Latex, v2: references added, version to appear in Nucl. Phys.

Exit from inflation and a paradigm for vanishing cosmological constant in self-tuning models

We propose a paradigm for the inflation and the vanishing cosmological constant in a unified way with the self-tuning solutions of the cosmological constant problem. Here, we consider a time-varying cosmological constant in self-tuning models of the cosmological constant. As a specific example, we demonstrate it with a 3-form field in 5D.Comment: 11 pages of LaTeX fil