Constraining heavy colored resonances from top-antitop quark events

Recent measurements of the top quark charge asymmetry at Tevatron disfavor the existence of flavor universal axigluons and colorons at 2 sigmas. In this letter we explore the possibility to reconcile the data with these models and use the charge asymmetry and the invariant mass distribution of top-antitop quark pair events to constrain the mass and couplings of massive color-octet gauge bosons decaying to top quarks.Comment: 4 pages, 4 figures. References added, final version to appear in Phys.Rev.

Possibilities for consumer government actions to support coffee producers

This is the final report of a study commissioned by the Belgian Secretary of State for Development Co-operation, with the purpose of outlining possible actions to be adopted by the European Union to ensure a better share of total coffee revenues to producers in developing countries. The way to improve the participation of coffee producers in the economic gains accrued in the world coffee market translates, ultimately, in their receiving a fair price for the commodity they supply. A fair price is not an abstract entity in itself, but - in the competitive world economy - is perhaps better defined as a market price that results from fair market conditions in the whole coffee producing chain. Because of this, as will be seen below, for improving the lot of coffee producers, this reports outlines proposals to take place in the consuming countries, particularly Europe. At first sight, it might seem a contradiction acting in one region to directly impact others, far away. The key to the logic of the argument lies in the definition in the previous paragraph. As we try to demonstrate, market conditions in the consuming-countries side of the coffee producing chain are not fair; the market failures and distortions ingenuously created there are responsible for the enormous asymmetry of gains in the two sides. Radical positive measures for the coffee farms must begin, ironically, in Brussels. The structure of this report is as follows. Section 2 introduces preliminary background considerations. A summary of the past and present experiences in the application of supply management schemes is the content of Section 3 . Section 4 is an introduction to the main issues in the analysis of the coffee market . Finally, section 5 presents the proposals for consumer government supporting actions, and suggestions for a series of detailed studies to support the actions.

Angular Inflation from Supergravity

We study supergravity inflationary models where inflation is produced along the angular direction. For this we express the scalar component of a chiral superfield in terms of the radial and the angular components. We then express the supergravity potential in a form particularly simple for calculations involving polynomial expressions for the superpotential and Kahler potential. We show for a simple Polonyi model the angular direction may give rise to a stage of inflation when the radial field is fixed to its minimum. We obtain analytical expressions for all the relevant inflationary quantities and discuss the possibility of supersymmetry breaking in the radial direction while inflating by the angular component.Comment: 7 pages, one figure. Final version. Title changed, two figures droppe

Challenging the pro-development role of trade agreements when remoteness counts: the Ecuadorian experience

The question whether global financial integration is beneficial for everyone remains highly disputed. It is often assumed that financial globalization involves threshold effects, where integration is worthwhile only when certain preconditions are met. However, it has also been noted that financial account liberalization also brings about considerable additional indirect benefits. These indirect benefits are often the same as the preconditions, such that there exists a complex two-way relationship between financial globalization and the preconditions/additional benefits. Such a relationship can lead to financial globalization traps, where some economies are trapped at a low level stable equilibrium, while others enjoy ever increasing financial integration. In this paper, we use de facto indicators of international financial integration to investigate if the dynamics of financial integration exhibit signs of such thresholds and traps. We present a parametric way of estimating these important parameters, based on recently developed sample splitting and threshold estimation methods. We find that there are indeed signs of multiple equilibriums if we look at the growth rates of total assets and liabilities. We also find that a group of countries are apparently caught in a high debt stock trap.

Hybrid natural inflation from non Abelian discrete symmetry

A spontaneously broken global discrete symmetry may have pseudo Goldstone modes associated with the spontaneous breaking of the approximate continuous symmetry of the low dimension terms in the Lagrangian. These provide natural candidates for an inflaton that can generate slow roll inflation. We show that, in the case of a non Abelian discrete symmetry, the pseudo Goldstone modes readily couple to further scalar fields in a manner that the end of inflation is determined by these additional scalar fields, generating hybrid inflation. We give a simple parameterisation of the inflationary potential in this case, determine the inflationary parameters resulting, and show that phenomenological successful inflation is possible while keeping the scale of symmetry breaking sub-Plankian. Unlike natural inflation the inflation scale can be very low. We construct two simple hybrid inflation models, one non supersymmetric and one supersymmetric. In the latter case no parameters need be chosen anomalously small.Comment: Accepted for publication in Phys. Lett.