All-optical control of surface plasmons by second-harmonic generation

Light with light control of surface plasmon polaritons is theoretically demonstrated. A barely simple and compact source of these waves consists in a finite number of slits (evenly spaced) perforating a metal film. The system scatters electromagnetic fields in one side of the metal film when it is illuminated from the opposite side by a polarized light source. High intensity light sources moreover efficiently generate light at second harmonic and higher frequencies in the metal led by optical nonlinearities. It is shown how the mixing of fields scattered by the slits from a weak beam at $\lambda$ wavelength, with the second harmonic fields generated by a high intensity $2 \lambda$ beam, creates a destructive interference of surface plasmons in one of the two possible directions of emission from the slits, while these are enhanced along the opposite direction. The unidirectional launching of surface plasmons is due to the different properties of symmetry at $\lambda$ whether they are linearly or nonlinearly generated. It is envisaged a nanodevice which might allow sending digital information codified in the surface plasmon field or be used to build ultra-narrow bandwidth surface plasmon frequency combs.Comment: 5 pages, 3 figures, Supplemental Materia

Pension Reform in Brazil: Transitional Issues in a Model with Endogenous Labor Supply

Brazilian PAYG system has been under financial stress and needs to be reformed. I use a computational general equilibrium model, with 55 overlapping generations to simulate macroeconomic and welfare impacts of alternative social security reforms. Transition turns out to have quite different redistributional effects for the generations involved depending on which tax is used to finance it. Under a variety of possible transitional schemes, there is no tax path that is strictly preferred by every generation.Social Security, Welfare, General Equilibrium, Macroeconomics, Overlapping Generation

Skinning the Cat: Education Distribution, Changes in the School Premium and Earnings Inequality

This paper applies the procedure in JUHN ET ALL (1993) to decompose changes in income inequality over time in terms of education-related causal factors: school premiums, educational distribution and residual changes. The main conclusion is that reductions in the school premiums have systematically had a negative impact on income inequality during the last twenty years. At the same time, education has become more unequally distributed for individuals below the median labor income level and more equally distributed for those above it. The combination of the two forces has reduced income dispersion for the top half of earners, and slightly increased it among the bottom half. This difference in trends of educational distribution lies behind an apparently stable profile of income inequality (considering the whole earnings distribution).

Reallocation of Resources within the National Productive System in Bolivia: A View from the Perspective of Tradable and Non-Tradable Goods

This paper explores Bolivia’s current unemployment situation taking into account the reallocation of resources within the aggregate supply. The origin of this internal imbalance is due to negative impacts of external real exchange rate (RER) shocks, as well as to changes in the destination of foreign direct investment (FDI) among different sectors of the economy. The model used to explain the imbalance is based on the Dependent Economy theoretical framework, in which production in a small open economy is disaggregated into tradable and non-tradable goods. Under this production scheme, any RER movement in terms of appreciation or depreciation produces a displacement of resources, either along the production possibilities frontier or through the unemployment zone. After demonstrating that the RER suffered an important appreciation in 1997, a model of the aggregate-supply function is constructed considering two variable outputs (tradable and non-tradable goods) and two variable inputs (capital and labor), suggesting in the end the existence of a slow restructuring process at the expense of unemployment of the labor force.Inter-sector labor mobility, Internal balance, Tradable-Nontradable (TNT) model

Leviathan as a Minority Shareholder: A Study of Equity Purchases by the Brazilian National Development Bank (BNDES), 1995-2003

There is a growing literature comparing the performance of private vs. state-owned companies. Yet, there is little work examining the effects of having the government as a minority shareholder of private companies. We conduct such a study using data for 296 publicly-traded corporations in Brazil, looking at the effects of equity purchases by the National Bank for Economic and Social Development (BNDES) on firm performance between 1995 and 2003. Our fixed-effects regressions show that BNDES's purchases of equity lead to increases in return on assets and investment in fixed assets. Finally, we find that the positive effect of BNDES' equity purchases is reduced when the target firms belong to state-owned and private pyramidal groups. Therefore, our argue that having development banks owning minority stakes can have a positive effect on performance as long as they promote long-term investments and are shielded from governmental interference and potential minority shareholder expropriation.

Public Policy and Economic Growth: Developing Neoclassical Implications

Why do the countries of the world display considerable disparity in long term growth rates? This paper examines the hypothesis that the answer lies in differences in national public policies which affect the incentives that individuals have to accumulate capital in both its physical and human forms. Our analysis shows that these incentive effects can induce large difference in long run growth rates. Since many of the key tax rates are difficult to measure, our procedure is an indirect one We work within a calibrated, two sector endogenous growth model, which has its origins in the microeconomic literature on human capital formation. We show that national taxation can substantially affect long run growth rates. In particular, for small open economies with substantial capital mobility, national taxation can readily lead to "development traps" (in which countries stagnate or regress) or to "growth miracles" (in which countries shift from little growth to rapid expansion) This influence of taxation on the rate of economic growth has important welfare implications: in basic endogenous growth models, the welfare cost of a 10 % increase in the rate of income tax can be 40 times larger than in the basic neoclassical model.

Expressing the Behavior of Three Very Different Concurrent Systems by Using Natural Extensions of Separation Logic

Separation Logic is a non-classical logic used to verify pointer-intensive code. In this paper, however, we show that Separation Logic, along with its natural extensions, can also be used as a specification language for concurrent-system design. To do so, we express the behavior of three very different concurrent systems: a Subway, a Stopwatch, and a 2x2 Switch. The Subway is originally implemented in LUSTRE, the Stopwatch in Esterel, and the 2x2 Switch in Bluespec