Development threshold, capital flows, and financial turbulence

We study capital flows in a panel of 130 countries, and derive the implications for the observed patterns of capital flows and capital controls before and into the crisis of 2008–11. We find that the size of capital flows is positively correlated with country's income level. In addition, capital flight has a non-linear relationship with the income level. Using the Hansen threshold estimation, we identify a three-stage threshold effect: for low-income countries (GDP per capita below US$3,000), capital flight increases as the income level rises; and only after the economy passes a threshold level (GDP per capita above US$ 5,000), capital flight declines with income. We conclude with a case study of Brazil and Korea, observing that the decisions to implement capital control measures tend to be pushed around by the feedbacks among economic growth, currency appreciation, and the global financial conditions

Coherent Exciton Lasing in ZnSe/ZnCdSe Quantum Wells?

A new mechanism for exciton lasing in ZnSe/ZnCdSe quantum wells is proposed. Lasing, occurring below the lowest exciton line, may be associated with a BCS-like condensed (coherent) exciton state. This state is most stable at low temperatures for densities in the transition region separating the exciton Bose gas and the coherent exciton state. Calculations show the gain region to lie below the exciton line and to be separated from the absorption regime by a transparency region of width, for example, about 80 meV for a 90 Angstrom ZnSe/Zn_(0.75)Cd_(0.25)Se quantum well. Experimental observation of the transparency region using differential spectroscopy would confirm this picture.Comment: 9 pages + 3 figs contained in 4 postscript files to appear Appl. Phys. Lett. March 13, 199