Von Neumann spin measurements with Rashba fields

We show that dynamics in spin-orbit coupling field simulates the von Neumann measurement of a particle spin. We demonstrate how the measurement influences the spin and coordinate evolution of a particle by comparing two examples of such a procedure. First example is a simultaneous measurement of spin components, $\sigma _{x}$ and $\sigma _{y}$, corresponding to non-commuting operators, which cannot be accurately obtained together at a given time instant due to the Heisenberg uncertainty ratio. By mapping spin dynamics onto a spatial walk such a procedure determines measurement-time averages of $\sigma _{x}$ and $\sigma _{y}$, which already can be precisely evaluated in a single short-time measurement. The other, qualitatively different, example is the spin of a one-dimensional particle in a magnetic field. Here the outcome depends on the angle between the spin-orbit coupling and magnetic fields. These results can be applied to studies of spin-orbit coupled cold atoms and electrons in solids.Comment: 6 figure

Pulse-pumped double quantum dot with spin-orbit coupling

We consider the full driven quantum dynamics of a qubit realized as spin of electron in a one-dimensional double quantum dot with spin-orbit coupling. The driving perturbation is taken in the form of a single half-period pulse of electric field. Spin-orbit coupling leads to a nontrivial evolution in the spin and charge densities making the dynamics in both quantities irregular. As a result, the charge density distribution becomes strongly spin-dependent. The transition from the field-induced tunneling to the strong coupling regime is clearly seen in the charge and spin channels. These results can be important for the understanding of the techniques for the spin manipulation in nanostructures.Comment: 6 figure

Partners or predators? : the impact of regional trade liberalization on Indonesia

The authors empirically assess regional integration and liberalization scenarios impact on Indonesia and other Pacific Rim economies, including the complete Uruguay Round, further global liberalization and the creation of the Association of Southeast Asian Nations (ASEAN) or Asia-Pacific Economic Cooperation (APEC) free trade areas. They consider how major international exchange rate realignments affect the world trade pattern, and Indonesia in particular. The analysis uses a multi-country, computable general equilibrium (CGE) model to quantify the trade liberalization impact on countries, sectors, and factors. The extended APEC-CGE model consists of nine linked country models: Indonesia, Malaysia, and Singapore (together), the Philippines, Thailand, China (including Hong Kong), Korea and Taiwan, Japan, the United States and the European Union. Each country model is linked through explicit bilateral trade flows modeling for each traded sector. The empirical results lead to several conclusions: a) eliminating tariff and non tariff barriers in industrial countries (especially the Multifibre Agreement) gives Asian developing countries the opportunity to expand exports and achieve productivity gains; b) creation of an APEC free trade area gives participants significant benefits, with little effect on nonmembers while creation of an ASEAN free trade area gives its members little benefit, thus ASEAN countries should work toward more liberalization under GATT or hasten the APEC free trade area creation; c) all economies gain the most from further multilateral liberalization; and d) major exchange rate realignments significantly affect bilateral trade balances and world trade volume and direction. However, they have less effect than trade liberalization on the internal production and trade structure. Sectoral protection andsubsidy rates vary greatly and their elimination yields significant efficiency gains. Changes in exchange rates have less effect.Trade Policy,Environmental Economics&Policies,Payment Systems&Infrastructure,Economic Theory&Research,Transport and Trade Logistics,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Economic Theory&Research,Environmental Economics&Policies,Trade and Regional Integration,Trade Policy

After the negotiations: assessing the impact of free trade agreements in Southern Africa

After protracted and difficult negotiations, agreement was recently reached on the dimensions of a South African-EU free trade deal. Because of South Africa's prominence in the sub-region, implementation of this agreement will have an impact not only on South Africa, but on all the SADC economies. This paper traces how this impact may be felt over time, using a multi-region model constructed to focus on the determination of sectoral and geographic trade patterns. By separatelymodeling South Africa and the rest of southern Africa, the model can be used to evaluate how alternative SADC regional trade strategies can influence how the EU deal affects the region's economies; by distinguishing among major trading partners (EU, North America, East Asia), the simulations can help illuminate how the trade deal will likely affect current trade patterns The empirical results lead to a number of conclusions: (1) trade creation dominates trade diversion for the region under all FTA arrangements; (2) the rest of southern Africa benefits from an FTA between the EU and South Africa — the recently signed bilateral agreement is not a “beggar thy neighbor” policy; (3) the rest of southern Africa gains more from zero-tariff access to EU markets than from a partial (50 percent) reduction in global tariffs; and (4) the South African economy is not large enough to serve as a growth pole for the region. Access to EU markets provides substantially bigger gains for the rest of southern Africa than does access to South Africa.Trade policy Africa., Free trade., South Africa.,

Low-Frequency Quantum Oscillations due to Strong Electron Correlations

The normal-state energy spectrum of the two-dimensional $t$-$J$ model in a homogeneous perpendicular magnetic field is investigated. The density of states at the Fermi level as a function of the inverse magnetic field $\frac{1}{B}$ reveals oscillations in the range of hole concentrations $0.08<x<0.18$. The oscillations have both high- and low-frequency components. The former components are connected with large Fermi surfaces, while the latter with van Hove singularities in the Landau subbands, which traverse the Fermi level with changing $B$. The singularities are related to bending the Landau subbands due to strong electron correlations. Frequencies of these components are of the same order of magnitude as quantum oscillation frequencies observed in underdoped cuprates.Comment: 10 pages, 3 figures, Proc. NSS-2013, Yalta. arXiv admin note: text overlap with arXiv:1308.056