1,831 research outputs found
Dynamics of Fluctuating Bose-Einstein Condensates
We present a generalized Gross-Pitaevskii equation that describes also the
dissipative dynamics of a trapped partially Bose condensed gas. It takes the
form of a complex nonlinear Schr\"odinger equation with noise. We consider an
approximation to this Langevin field equation that preserves the correct
equilibrium for both the condensed and the noncondensed parts of the gas. We
then use this formalism to describe the reversible formation of a
one-dimensional Bose condensate, and compare with recent experiments. In
addition, we determine the frequencies and the damping of collective modes in
this case.Comment: 4 pages of REVTeX, including 4 figure
Competition for Traders and Risk
Abstract: The financial crisis has been attributed partly to perverse incentives for traders at banks and has led policy makers to propose regulation of banksā remuneration packages. We explain why poor incentives for traders cannot be fully resolved by only regulating the bankās top executives, and why direct intervention in trader compensation is called for. We present a model with both trader moral hazard and adverse selection on trader abilities. We demonstrate that as competition on the labour market for traders intensifies, banks optimally offer top traders contracts inducing them to take more risk, even if banks fully internalize the costs of negative outcomes. In this way, banks can reduce the surplus they have to offer to lower ability traders. In addition, we find that increasing banksā capital requirements does not unambiguously lead to reduced risk-taking by their top traders.optimal contracts;remuneration policy;imperfect competition;financial institutions;risk
Competition Leverage: How the Demand Side Affects Optimal Risk Adjustment
We study optimal risk adjustment in imperfectly competitive health insurance markets when high-risk consumers are less likely to switch insurer than low-risk consumers. First, we find that insurers still have an incentive to select even if risk adjustment perfectly corrects for cost differences among consumers. Consequently, the outcome is not efficient even if cost differences are fully compensated. To achieve first best, risk adjustment should overcompensate for serving high-risk agents to take into account the difference in mark- ups among the two types. Second, the difference in switching behavior creates a trade off between efficiency and consumer welfare. Reducing the difference in risk adjustment subsidies to high and low types increases consumer welfare by leveraging competition from the elastic low-risk market to the less elastic high-risk market. Finally, mandatory pooling can increase consumer surplus even further, at the cost of efficiency.health insurance;risk adjustment;imperfect competition;leverage
Selective Contracting and Foreclosure in Health Care Markets
We analyze exclusive contracts between health care providers and insurers in a model where some consumers choose to stay uninsured. In case of a monopoly insurer, exclusion of a provider changes the distribution of consumers who choose not to insure. Although the foreclosed care provider remains active in the market for the non-insured, we show that exclusion leads to anti-competitive effects on this non-insured market. As a consequence exclusion can raise industry profits, and then occurs in equilibrium. Under competitive insurance markets, the anticompetitive exclusive equilibrium survives. Uninsured consumers, however, are now not better off without exclusion. Competition among insurers raises prices in equilibria without exclusion, as a result of a horizontal analogue to the double marginalization effect. Instead, under competitive insurance markets exclusion is desirable as long as no provider is excluded by all insurers.health insurance;uninsured;selective contracting;exclusion;foreclosure;anti-competitive effects
Collective Modes in a Dilute Bose-Fermi Mixture
We here study the collective excitations of a dilute spin-polarized
Bose-Fermi mixture at zero temperature, considering in particular the features
arising from the interaction between the two species. We show that a
propagating zero-sound mode is possible for the fermions even when they do not
interact among themselves.Comment: latex, 6 eps figure
Extended molecules and geometric scattering resonances in optical lattices
We develop a theory describing neutral atoms scattering at low energies in an
optical lattice. We show that for a repulsive interaction, as the microscopic
scattering length increases, the effective scattering amplitude approaches a
limiting value which depends only on the lattice parameters. In the case of
attractive interaction a geometric resonance occurs before reaching this limit.
Close to the resonance, the effective interaction becomes repulsive and
supports a weakly bound state, which can extend over several lattice sites.Comment: 4 pages, 1 figure, RevTe
Induction of morphological aberrations by enzyme inhibition in Drosophila melanogaster
Zusatz zum Futter vonDrosophila melanogaster von 5-Fluoro-2-deoxyuridin oder Aminopterin induziert Ć¼berzƤhlige Skutellar- und Dorsozentralborsten sowie gekerbte FlĆ¼gel. Diese Modifikationen wurden als Konsequenz von Enzymhemmung interpretiert
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