Can non-linear real shocks explain the persistence of PPP exchange rate disequilibria?

A core stylized fact of the empirical exchange rate literature is that half-life deviations of equilibrium real exchange rates from levels implied by Purchasing Power Parity (PPP) are very persistent. Empirical efforts to explain this persistence typically proceed along two distinct paths, resorting either to the presence of real shocks such as productivity differentials that drive equilibrium exchange rates away from levels implied by PPP, or the presence of non-linearities in the adjustment process around PPP. By contrast, we combine these two explanations in the context of an innovative panel estimation methodology. We conclude that both explanations are relevant to the behavior of exchange rates and that resulting half-lives are much shorter than estimated using linear PPP and more consistent with the observed volatility of nominal and real exchange rates. JEL Classification: F31, C23, L6-L9Balassa-Samuelson, EPSTAR, exchange rate, PPP, productivity

Relaxation Methods for Mixed-Integer Optimal Control of Partial Differential Equations

We consider integer-restricted optimal control of systems governed by abstract semilinear evolution equations. This includes the problem of optimal control design for certain distributed parameter systems endowed with multiple actuators, where the task is to minimize costs associated with the dynamics of the system by choosing, for each instant in time, one of the actuators together with ordinary controls. We consider relaxation techniques that are already used successfully for mixed-integer optimal control of ordinary differential equations. Our analysis yields sufficient conditions such that the optimal value and the optimal state of the relaxed problem can be approximated with arbitrary precision by a control satisfying the integer restrictions. The results are obtained by semigroup theory methods. The approach is constructive and gives rise to a numerical method. We supplement the analysis with numerical experiments

Organochlorine Pesticide Contamination in New World Passerines

Organochlorine pesticide contaminants detrimentally affect wildlife in many ways, including lowered reproductive success, endocrine disruption, and embryonic defects. Most organochlorine pesticides have been banned in the United States after the recognition of these effects. However, these pesticides are still used in Central and South America, and little information is available concerning the levels of pesticide contamination in wildlife from these areas. Furthermore, little data exist regarding organochlorine pesticide contamination in passerines (songbirds). The purpose of this study was to determine the presence in passerines of organochlorine pesticides that are of concern to the Environmental Protection Agency. Neotropical resident species (i.e. those living year-round Central and South America) were collected from Argentina and Peru in 1996, Neotropical migrant species (i.e. those that winter in Central and South America and breed in North America) were collected in central and western Illinois from 1991-1996, and Nearctic resident species (i.e. those living year-round in North America) were collected in central Illinois in 1995 and 1996. Contamination levels were compared between each of the above geographic locations. Predominate pesticides found in Nearctic resident and Neotropical migrant species included DDE, dieldrin and heptachlor epoxide. No significant levels of organochlorine pesticides were found in the Neotropical resident birds. Significantly higher pesticide levels were found in Neotropical migrants than in Neotropical residents. No difference was found in pesticide levels among the Neotropical migrants in relation to age class. These findings suggest that passerines may be acquiring organochlorine pesticides in North America

Ghoshal’s Ghost: Financialization and the End of Management Theory

Sumantra Ghoshal’s condemnation of “bad management theories” that were “destroying good management practices” has not lost any of its salience, after a decade. Management theories anchored in agency theory (and neo-classical economics generally) continue to abet the financialization of society and undermine the functioning of business. An alternative approach (drawn from a more classic institutional, new ecological, and refocused ethical approaches) is reviewed

Superconductivity and Non-Classical Long-Range Order on a Quantum Computer

An important problem in quantum information is the practical demonstration of non-classical long-range order on quantum computers. One of the best known examples of a quantum system with non-classical long-range order is a superconductor. Here we achieve Cooper pairing of qubits on a quantum computer to represent superconducting or superfluid states. We rigorously confirm the quantum long-range order by measuring the large $O(N)$ eigenvalue of the two-electron reduced density matrix. The demonstration of maximal quantum long-range order is an important step towards more complex modeling of superconductivity and superfluidity as well as other phenomena with significant quantum long-range order on quantum computers