The Interrelationship between Exchange Rates and Stock Prices: Evidence from China

For more than 30 years, the relationship between stock prices and foreign exchange rates has drawn attention of economists, because they both play crucial roles in influencing the development of a country's economy. Many studies have been conducted both theoretically and empirically. So far, the research thus far has extended the inquiry into the stock market and exchange rate relations across developed and emerging economies to bring a broadly-based insight into the issue and to fill the gap in the literature. However, the China's market is rarely included in the existing literature. The main objective of this study is to examine the relationship between stock prices and RMB exchange rates in China. The sample period for this study is from Jan 1, 2002 to Jul 31,2009, and the weekly data of Shanghai and Shenzhen A share stock index and RMB exchange rate against U.S. dollar, Euro and Japanese Yen were gathered from Datastream. During the data period, the range of Shanghai A share is from 1066 to 6396 points, and the range of Shenzhen A share is from 246 to 1660 points during the data period. And at the same time, the RMB exchange rates also changed dramatically, especially before and after the reform of RMB exchange rate formation mechanism on Jul 21, 2005. According to this, the data are divided and examined by two parts, that is before and after the China's exchange rate reform. The models applied in this study includes Augmented Dickey-Fuller Test, Engle and Granger Two-step Test and Granger Causality Test. The results show that, first, in terms of the broad relationship the relationship between the exchange rate and stock price are either positive or negative, and the relationships are opposite before and after the reform. Second, there is no sign indicating that the Chinese exchanges rates and stock prices become more connected after the reform. What's more, before the reform, Shenzhen A share stock index is more connected with RMB exchange rates and their relationships are negative. While, after the reform, Shanghai A share stock index is comparatively more connected with RMB exchange rates and their relationships become positive. Finally, the Granger causal order is found between some pairs of variables, that is the RMB exchange rate with Japanese Yen is the Granger Cause of Shanghai stock price before the exchange rate reform and is Granger Cause of both Shanghai stock price and Shenzhen Stock price after the reform. While, for another direction, before the reform, Shenzhen A share stock index is the Granger cause for RMB exchange rate with U.S. dollar. However, after the reform, there is no causal relationship between these two variables

Cavity-Assisted Dynamical Spin-Orbit Coupling in Cold Atoms

We consider ultracold atoms subjected to a cavity-assisted two-photon Raman transition. The Raman coupling gives rise to effective spin-orbit interaction which couples atom's center-of-mass motion to its pseudospin degrees of freedom. Meanwhile, the cavity photon is dynamically affected by the atom. This feedback between atom and photon leads to a dramatic modification of the atomic dispersion relation, and further leads to dynamical instability of the system. We propose to detect the change of cavity photon number as a direct way to demonstrate dynamical instability.Comment: 5 pages, 5 figure

Sound speed of a Bose-Einstein condensate in an optical lattice

The speed of sound of a Bose-Einstein condensate in an optical lattice is studied both analytically and numerically in all three dimensions. Our investigation shows that the sound speed depends strongly on the strength of the lattice. In the one-dimensional case, the speed of sound falls monotonically with increasing lattice strength. The dependence on lattice strength becomes much richer in two and three dimensions. In the two-dimensional case, when the interaction is weak, the sound speed first increases then decreases as the lattice strength increases. For the three dimensional lattice, the sound speed can even oscillate with the lattice strength. These rich behaviors can be understood in terms of compressibility and effective mass. Our analytical results at the limit of weak lattices also offer an interesting perspective to the understanding: they show the lattice component perpendicular to the sound propagation increases the sound speed while the lattice components parallel to the propagation decreases the sound speed. The various dependence of the sound speed on the lattice strength is the result of this competition.Comment: 15pages 6 figure

Nuclear-nuclear interaction mediated by a mechanically controlled nitrogen-vacancy-center spin in diamond

We propose a scheme to achieve nuclear-nuclear indirect interactions mediated by a mechanically driven nitrogen-vacancy (NV) center in diamond. Here we demonstrate two-qubit entangling gates and quantum-state transfer between two carbon nuclei in diamond. In such a system, the NV center interacts with a nearby nuclear spin via a dipole-dipole interaction. Under the quantum Zeno condition, the scheme is robust against decoherence caused by coupling between the NV center (nuclear spins) and the environment. Conveniently, precise control of dipole coupling is not required so this scheme is insensitive to fluctuating positions of the nuclear spins and the NV center. Our scheme provides a general blueprint for multi-nuclear-spin gates and for multi-party communication in a polygon geometry with each vertex occupied by a nuclear spin.Comment: 11 pages, 8 figure

Optimal tracking control for uncertain nonlinear systems with prescribed performance via critic-only ADP

This paper addresses the tracking control problem for a class of nonlinear systems described by Euler-Lagrange equations with uncertain system parameters. The proposed control scheme is capable of guaranteeing prescribed performance from two aspects: 1) A special parameter estimator with prescribed performance properties is embedded in the control scheme. The estimator not only ensures the exponential convergence of the estimation errors under relaxed excitation conditions but also can restrict all estimates to pre-determined bounds during the whole estimation process; 2) The proposed controller can strictly guarantee the user-defined performance specifications on tracking errors, including convergence rate, maximum overshoot, and residual set. More importantly, it has the optimizing ability for the trade-off between performance and control cost. A state transformation method is employed to transform the constrained optimal tracking control problem to an unconstrained stationary optimal problem. Then a critic-only adaptive dynamic programming algorithm is designed to approximate the solution of the Hamilton-Jacobi-Bellman equation and the corresponding optimal control policy. Uniformly ultimately bounded stability is guaranteed via Lyapunov-based stability analysis. Finally, numerical simulation results demonstrate the effectiveness of the proposed control scheme