Currency Crises: Is Central America Different?

In a recent paper we analyzed the determinants of currency crises in a sample of 30 high and middle income countries (Esquivel and Larrain, 1998). In this work we focus on Central America and analyze whether the determinants of currency crises in this region are different from those identified in our previous work. We conclude that they are not, and show that a small set of macroeconomic variables helps to explain the currency crises that took place in Central America between 1976 and 1996. The results of tests applied here support the empirical approach that attempts to explain currency crises by focusing on the behavior of a few macroeconomic indicators. Part of the interest of this result stems from the fact that the Central American countries had an exchange rate system markedly different from that prevailing in the economies that are usually analyzed in similar studies.

THE IMPACT OF G-3 EXCHANGE RATE VOLATILITY ON DEVELOPING COUNTRIES,

This paper describes G-3 exchange rate volatility and evaluates its impact on developing countries. The paper presents empirical evidence showing that G-3 exchange rate volatility has a robust and significantly negative impact on developing countries’ exports. A one percentage point increase in G-3 exchange rate volatility decreases real exports of developing countries by about 2 per cent, on average. G-3 exchange rate volatility also appears to have a negative influence on foreign direct investment to certain regions, and increases the probability of occurrence of exchange rate crises in developing countries. These results imply that greater stability in the international exchange rate system would help improve trade and foreign direct investment prospects for developing countries – and would help prevent currency crises.

Wave breaking and particle jets in intense inhomogeneous charged beams

This work analyzes the dynamics of inhomogeneous, magnetically focused high-intensity beams of charged particles. While for homogeneous beams the whole system oscillates with a single frequency, any inhomogeneity leads to propagating transverse density waves which eventually result in a singular density build up, causing wave breaking and jet formation. The theory presented in this paper allows to analytically calculate the time at which the wave breaking takes place. It also gives a good estimate of the time necessary for the beam to relax into the final stationary state consisting of a cold core surrounded by a halo of highly energetic particles.Comment: Accepted in Physics of Plasma Letter

Superconducting pipes and levitating magnets

Motivated by a beautiful demonstration of the Faraday's and Lenz's law in which a small neodymium magnet falls slowly through a conducting non-ferromagnetic tube, we consider the dynamics of a magnet falling through a superconducting pipe. Unlike the case of normal conducting pipes, in which the magnet quickly reaches the terminal velocity, inside a superconducting tube the magnet falls freely. On the other hand, to enter the pipe the magnet must overcome a large electromagnetic energy barrier. For sufficiently strong magnets, the barrier is so large that the magnet will not be able to penetrate it and will be suspended over the front edge. We calculate the work that must done to force the magnet to enter a superconducting tube. The calculations show that superconducting pipes are very efficient at screening magnetic fields. For example, the magnetic field of a dipole at the center of a short pipe of radius $a$ and length $L \approx a$ decays, in the axial direction, with a characteristic length $\xi \approx 0.26 a$. The efficient screening of the magnetic field might be useful for shielding highly sensitive superconducting quantum interference devices, SQUIDs. Finally, the motion of the magnet through a superconducting pipe is compared and contrasted to the flow of ions through a trans-membrane channel

Optical signatures of quantum delocalization over extended domains in photosynthetic membranes

The prospect of coherent dynamics and excitonic delocalization across several light-harvesting structures in photosynthetic membranes is of considerable interest, but challenging to explore experimentally. Here we demonstrate theoretically that the excitonic delocalization across extended domains involving several light-harvesting complexes can lead to unambiguous signatures in the optical response, specifically, linear absorption spectra. We characterize, under experimentally established conditions of molecular assembly and protein-induced inhomogeneities, the optical absorption in these arrays from polarized and unpolarized excitation, and demonstrate that it can be used as a diagnostic tool to determine the coherent coupling among iso-energetic light-harvesting structures. The knowledge of these couplings would then provide further insight into the dynamical properties of transfer, such as facilitating the accurate determination of F\"orster rates.Comment: 4 figures and Supplementary information with 7 figures. To appear in Journal of physical chemistry A, 201