Examples of N=2 to N=1 supersymmetry breaking

In this paper we consider gauged N=2 supergravities which arise in the low-energy limit of type II string theories and study examples which exhibit spontaneous partial supersymmetry breaking. For the quantum STU model we derive the scalar field space and the scalar potential of the N=1 supersymmetric low-energy effective action. We also study the properties of the Minkowskian N=1 supersymmetricground states for a broader class of supergravities including the quantum STU model.Comment: 22 pages, added references, version to appear in JHE

Estimation of real equilibrium exchange rates.

The purpose of this paper is to provide a consistent and transparent theoretical and empirical framework to analyse real effective equilibrium exchange rates for a large number of industrial countries. The theoretical and empirical model, as well as the applied methodology, are closely related to a recently published working paper by the IMF (Alberola et.al (1999)).In the theoretical part, a macroeconomic model of internal and external equilibrium is presented (chapters 2, 3 and 4). The empirical part estimates a simplified version of the theoretical model and results are thereafter reported and evaluated on a country by country basis (chapter 5). The purpose of the empirical part is not to arrive at point estimates for equilibrium exchange rates, but rather to provide some basic econometric evidence as a complement and illustration of the theoretical analysis. The empirical model and statistical methodology is kept simple and uniform for all countries in order to facilitate interpretation and evaluation of the results.exchange rates, modelling

Failure and avalanches in complex networks

We study the size distribution of power blackouts for the Norwegian and North American power grids. We find that for both systems the size distribution follows power laws with exponents $-1.65 \pm 0.05$ and $-2.0 \pm 0.1$ respectively. We then present a model with global redistribution of the load when a link in the system fails which reproduces the power law from the Norwegian power grid if the simulation are carried out on the Norwegian high-voltage power grid. The model is also applied to regular and irregular networks and give power laws with exponents $-2.0\pm0.05$ for the regular networks and $-1.5\pm0.05$ for the irregular networks. A presented mean field theory is in good agreement with these numerical results.Comment: Added new references and some minor extentions on request from referee. Changed figure order. Added journal re