Unified derivation of Bohmian methods and the incorporation of interference effects

We present a unified derivation of Bohmian methods that serves as a common starting point for the derivative propagation method (DPM), Bohmian mechanics with complex action (BOMCA) and the zero-velocity complex action method (ZEVCA). The unified derivation begins with the ansatz $\psi=e^{\frac{iS}{\hbar}}$ where the action, $S$, is taken to be complex and the quantum force is obtained by writing a hierarchy of equations of motion for the phase partial derivatives. We demonstrate how different choices of the trajectory velocity field yield different formulations such as DPM, BOMCA and ZEVCA. The new derivation is used for two purposes. First, it serves as a common basis for comparing the role of the quantum force in the DPM and BOMCA formulations. Second, we use the new derivation to show that superposing the contributions of real, crossing trajectories yields a nodal pattern essentially identical to that of the exact quantum wavefunction. The latter result suggests a promising new approach to deal with the challenging problem of nodes in Bohmian mechanics

Structural and electronic influences on phosphite basicity and its application to heterogeneous and homogeneous catalysis

NiL(,4) complexes of various monocyclic and bicyclic phosphite ligands have been shown to be effective catalysts for the isomerization and hydrocyanation of olefins. The catalytic activity of the NiL(,4) complex was found to be dependent upon the electronic and structural properties of the phosphite ligand. It was observed that in order for these complexes to function as catalysts, the presence of either a protic or a Lewis acid co-catalyst was required.;An x-ray structural investigation of a NiL(,4) complex containing a monocyclic phosphite showed that the complex is tetrahedrally coordinated. It is suggested that the marked difference in catalytic activity of these complexes is derived from the differences in the steric properties of the ligands contained in the complex.;Attempts were also made at heterogenizing these homogeneous NiL(,4) catalysts by means of ligand exchange with nonchelating diphosphorus ligands (P-P). Complexes of the following types were prepared and (UNFORMATTED TABLE FOLLOWS); L L L;-Ni-(P-P)-Ni-(P-P)-Ni-; L L L(TABLE ENDS);evaluated as catalysts for olefin isomerization under the same conditions used with the homogeneous NiL(,4) catalysts.;The structural and electronic properties of some selected monocyclic aminophosphite compounds were investigated in order to determine how their unique electronic and structural properties could influence the catalytic activities of the NiL(,4) compounds they formed.;A method for the quantitative analysis of alcohols using phosphorus-containing derivatizing reagents was developed. This method entailed the use of quantitative (\u2731)P NMR techniques

Trade policy reform and poverty alleviation

In this paper, developed as part of the World Bank's Poverty Reduction Strategy Sourcebook, the authors examine how to implement trade liberalization as part of a strategy for alleviating poverty in developing countries. They discuss trade policy instruments, institutions, complementary policies, sector issues, adjustment policies, and safety nets in an integrated approach to trade policy as a tool for poverty alleviation. The authors examine the patterns or models of trade policy that have been successful in alleviating poverty. They discuss the role of tariffs, nontariff barriers, contingent protection (such as safeguards and antidumping), special import regimes (such as duty drawback), export taxes, export subsidies, and trade-related institutions (such as standards, marketing, export finance, customs clearance, and regional trade arrangements). The authors also discuss policies that complement successful trade reform, including macroeconomic stability, a competitive exchange rate, flexible labor markets, competitive product markets, and policies that do not discriminate against foreigners in investment. They suggest approaches to policies and institutions in services and agriculture, key sectors in poverty reduction. They explain the roles of retraining and safety nets in dealing with the adjustment costs of trade liberalization. Finally, the authors elaborate guidelines for implementing trade reform and explain tools for assessing whether trade reform will help or harm the poor in particular sectors in the short run.Environmental Economics&Policies,Payment Systems&Infrastructure,Economic Theory&Research,Trade Policy,Labor Policies,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Environmental Economics&Policies,Economic Theory&Research,Trade Policy,Achieving Shared Growth

Complex trajectory method in time-dependent WKB

We present a significant improvement to a time-dependent WKB (TDWKB) formulation developed by Boiron and Lombardi [JCP {\bf108}, 3431 (1998)] in which the TDWKB equations are solved along classical trajectories that propagate in the complex plane. Boiron and Lombardi showed that the method gives very good agreement with the exact quantum mechanical result as long as the wavefunction does not exhibit interference effects such as oscillations and nodes. In this paper we show that this limitation can be overcome by superposing the contributions of crossing trajectories. We also demonstrate that the approximation improves when incorporating higher order terms in the expansion. These improvements could make the TDWKB formulation a competitive alternative to current time-dependent semiclassical methods

Optimal Design Of English Auctions With Discrete Bid Levels

This paper considers a form of ascending price English auction widely used in both live and online auctions. This discrete bid auction requires that the bidders submit bids at predetermined discrete bid levels, and thus, there exists a minimal increment by which the bid price may be raised. In contrast, the academic literature of optimal auction design deals almost solely with continuous bid auctions. As a result, there is little practical guidance as to how an auctioneer, seeking to maximize its revenue, should determine the number and value of these discrete bid levels, and it is this omission that is addressed here. To this end, a model of a discrete bid auction from the literature is considered, and an expression for the expected revenue of this auction is derived. This expression is used to determine both numerical and analytical solutions for the optimal bid levels, and uniform and exponential bidder’s valuation distributions are compared. Finally, the limiting case where the number of discrete bid levels is large is considered. An analytical expression for the distribution of the optimal discrete bid levels is derived, and an intuitive understanding of how this distribution maximizes the revenue of the auction is developed

Bragg Scattering as a Probe of Atomic Wavefunctions and Quantum Phase Transitions in Optical Lattices

We have observed Bragg scattering of photons from quantum degenerate $^{87}$Rb atoms in a three-dimensional optical lattice. Bragg scattered light directly probes the microscopic crystal structure and atomic wavefunction whose position and momentum width is Heisenberg-limited. The spatial coherence of the wavefunction leads to revivals in the Bragg scattered light due to the atomic Talbot effect. The decay of revivals across the superfluid to Mott insulator transition indicates the loss of superfluid coherence.Comment: 5 pages, 4 figure