2,680 research outputs found
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
Preparation of an Exciton Condensate of Photons on a 53-Qubit Quantum Computer
Quantum computation promises an exponential speedup of certain classes of
classical calculations through the preparation and manipulation of entangled
quantum states. So far most molecular simulations on quantum computers,
however, have been limited to small numbers of particles. Here we prepare a
highly entangled state on a 53-qubit IBM quantum computer, representing 53
particles, which reveals the formation of an exciton condensate of photon
particles and holes. While elusive for more than 50 years, such condensates
were recently achieved for electron-hole pairs in graphene bilayers and metal
chalcogenides. Our result with a photon condensate has the potential to further
the exploration of this new form of condensate that may play a significant role
in realizing efficient room-temperature energy transport
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 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
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