Trade and Linked Exchange; Price Discrimination Through Transaction Bundling

In this paper we try to explain how price discrimination can cause bilateral trade patterns of the type seen under countertrade agreements. We interpret countertrade as a form of transaction bundling which can discriminate between potential trading partners and we combine characteristics from both explanations as to the existence of countertrade. There is both price discrimination through transaction bundling, and informational asymmetry in the form of uncertainty in the quality of the goods produced by trading partners in less developed countries (LDCs) leading to a partner preference from the side of the Western (DC) firm. Our paper shows that although the ability of firms in LDCs to overcome their creditworthiness constraints by engaging in countertrade arrangements may be restricted by this quality uncertainty as it reduces the willingness of a firm in a DC to exchange, the trade volume prospects of a firm in a LDC can be considerably enhanced if a countertrade transaction does occur. Our paper goes beyond the case of linked exchange, which is only one of the three cases of transaction bundling examined. The other two cases are that of the Western firm being a monopoly selling a bundle of two goods used as a benchmark case, and the more interesting case of the Western firm being the buyer of two goods and setting both two separate buying prices and a bundling (i.e. package) purchase price. Many procurement decisions are not simply a matter of price, but also the identity and reputation of the supplier matters, especially when the supplier is located in an LDC. We show than when bundling its purchases, the Western firm buyer will be willing to offer a bundled price greater than the sum of the two separate prices, as the option of a bundled purchase would increase its pro…ts even if there are no complementarities between the goods bundled. In our model the argument is that just as it is profitable for a monopolist to offer mixed bundling at a bundled price which is lower than the sum of the individual prices (hence exploiting the average willingness to pay), it is also profitable for a monopsonist to offer a bundled purchase price which is higher that the sum of the individual prices on offer (hence exploiting the average willingness to sell). Equally interestingly, it is found that a LDC can substantially increase its sales of a good with a high degree of quality uncertainty by being offered to bundle it with the sale of a more basic good with a low degree of quality uncertainty

Partial scaling transform of multiqubit states as a criterion of separability

The partial scaling transform of the density matrix for multiqubit states is introduced to detect entanglement of quantum states. The transform contains partial transposition as a special case. The scaling transform corresponds to partial time scaling of subsystem (or partial Planck's constant scaling) which was used to formulate recently separability criterion for continous variables.A measure of entanglement which is a generalization of negativity measure is introduced being based on tomographic probability description of spin states.Comment: 16 pages, 5 figures, submitted to J. Phys. A: Math. Ge

Prediction of airfoil stall using Navier-Stokes equations in streamline coordinates

A Navier-Stokes procedure to calculate the flow about an airfoil at incidence was developed. The parabolized equations are solved in the streamline coordinates generated for an arbitrary airfoil shape using conformal mapping. A modified k-epsilon turbulence model is applied in the entire domain, but the eddy viscosity in the laminar region is suppressed artificially to simulate the region correctly. The procedure was applied to airfoils at various angles of attack, and the results are quite satisfactory for both laminar and turbulent flows. It is shown that the present choice of the coordinate system reduces the error due to numerical diffusion, and that the lift is accurately predicted for a wide range of incidence

A method to find quantum noiseless subsystems

We develop a structure theory for decoherence-free subspaces and noiseless subsystems that applies to arbitrary (not necessarily unital) quantum operations. The theory can be alternatively phrased in terms of the superoperator perspective, or the algebraic noise commutant formalism. As an application, we propose a method for finding all such subspaces and subsystems for arbitrary quantum operations. We suggest that this work brings the fundamental passive technique for error correction in quantum computing an important step closer to practical realization.Comment: 5 pages, to appear in Physical Review Letter

The growth of galaxies in cosmological simulations of structure formation

We use hydrodynamic simulations to examine how the baryonic components of galaxies are assembled, focusing on the relative importance of mergers and smooth accretion in the formation of ~L_* systems. In our primary simulation, which models a (50\hmpc)^3 comoving volume of a Lambda-dominated cold dark matter universe, the space density of objects at our (64-particle) baryon mass resolution threshold, M_c=5.4e10 M_sun, corresponds to that of observed galaxies with L~L_*/4. Galaxies above this threshold gain most of their mass by accretion rather than by mergers. At the redshift of peak mass growth, z~2, accretion dominates over merging by about 4:1. The mean accretion rate per galaxy declines from ~40 M_sun/yr at z=2 to ~10 M_sun/yr at z=0, while the merging rate peaks later (z~1) and declines more slowly, so by z=0 the ratio is about 2:1. We cannot distinguish truly smooth accretion from merging with objects below our mass resolution threshold, but extrapolating our measured mass spectrum of merging objects, dP/dM ~ M^a with a ~ -1, implies that sub-resolution mergers would add relatively little mass. The global star formation history in these simulations tracks the mass accretion rate rather than the merger rate. At low redshift, destruction of galaxies by mergers is approximately balanced by the growth of new systems, so the comoving space density of resolved galaxies stays nearly constant despite significant mass evolution at the galaxy-by-galaxy level. The predicted merger rate at z<~1 agrees with recent estimates from close pairs in the CFRS and CNOC2 redshift surveys.Comment: Submitted to ApJ, 35 pp including 15 fig