Casimir-Polder forces in the presence of the cosmic photon heat bath

We study the effect of a photon background at finite temperature $T$ on the Van der Waals interactions among neutral bodies. It turns out that the long-range Casimir-Polder force is unaffected for distances much less than $T^{-1}$ and strongly enhanced for distances much above $T^{-1}$.Comment: 8 pages, 2 figure

THE WELFARE REFORM BILL AND ITS EFFECTS IN THE SOUTH

Political Economy,

The Tragedy of the Commons in a Fishery when Relative Performance Matters

This paper presents a simple model of a common access fishery where fishermen care about relative performance as well as absolute profits. Our specification captures the idea that status (which depends on relative performance) in a community infuences a person's well-being. We consider two alternative specifications of relative performance. In our first specication, relative performance is equated to relative after-tax profits. In our second specification, it is relative harvests that matter. We show that overharvesting resulting from the tragedy of the commons problem is exacerbated by the desire for higher relative performance, leading to a smaller steady-state fish stock and smaller steady-state profit for all the fishermen. We examine a tax package, consisting of a tax on relative profit and a tax on effort, and an individual quota as alternatives to implement the socially effcient equilibrium.relative income, relative performance, status, fishery, tragedy of the commons

The structural dependence of the effective mass and Luttinger parameters in semiconductor quantum wells

A detailed comparison of the empirical pseudopotential method with single and multiple band calculations based on the envelope function and effective mass approximations are presented. It is shown that, in order to give agreement with the more rigorous microscopic approach of the pseudopotential method, structural dependent effective masses and Luttinger parameters must be invoked. The CdTe/Cd(1 – x)Mn(x)Te system has been employed as an example, and the first pseudopotential calculations of quantum wells and superlattices in this material are presented. It is shown that the electron, light- and heavy-hole effective masses tend towards twice their bulk values in the limit of narrow quantum wells. © 1997 American Institute of Physics