Universal Soft Terms in the MSSM on D-branes

In Type II string vacua constructed from intersecting/magnetized D-branes, the supersymmetry-breaking soft terms are genericaly non-universal. It is shown that universal supersymmetry-breaking soft terms may arise in a realistic MSSM constructed from intersecting/magnetized D-branes in Type II string theory. For the case of dilaton-dominated supersymmetry-breaking, it is shown that the universal scalar mass and trilinear coupling are fixed such that $m_0=(1/2)m_{3/2}$ and $A_0 = - m_{1/2}$. In addition, soft terms where the universal scalar mass $m_0$ is much larger than the universal gaugino mass $m_{1/2}$ may be easily obtained within the model, corresponding to the Focus Point (FP)/Hyperbolic Branch (HB) regions of the mSUGRA/CMSSM parameter space. Finally, it is shown that the special dilaton and no-scale strict moduli boundary conditions, which are well-known in heterotic string constructions, may also be obtained.Comment: Version published in Nuclear Physics

Learning relationships from theory to design

This paper attempts to bridge the psychological and anthropological views of situated learning by focusing on the concept of a learning relationship, and by exploiting this concept in our framework for the design of learning technology. We employ Wenger's (1998) concept of communities of practice to give emphasis to social identification as a central aspect of learning, which should crucially influence our thinking about the design of learning environments. We describe learning relationships in terms of form (one‐to‐one, one‐to‐many etc.), nature (explorative, formative and comparative), distance (first‐, second‐order), and context, and we describe a first attempt at an empirical approach to their identification and measurement

The Value of Publishing Official Central Bank Forecasts

The aim of the present analysis is to shed light on the question whether Central Banks should publish their macroeconomic forecasts, and what could possibly be gained in monetary policy if they did so. We show that disclosing the Central Bank’s assessment of the prevailing inflationary pressures in the form of a forecast improves macroeconomic performance even if this assessment is imprecise. This is because it makes policy more predictable. We are also interested in finding out the useful content of the forecasts, if published, and answering the question whether it makes a difference if these official forecasts are “unconditional” in the sense of incorporating the Central Bank’s forecasts of its own policy as well, or “conditional” on some other policy assumption. Possible conditional alternatives may include assuming unchanged instruments, however specified, or assuming the kind of policy that the private sector is estimated to expect. The analysis comes out in favour of publishing unconditional forecasts, which reveal the intended results of monetary policy. A discussion of some practical issues related to publishing official macroeconomic forecasts is also provided.forecasting; transparency; monetary policy; central banks