Dark solitons, dispersive shock waves, and transverse instabilities

The nature of transverse instabilities to dark solitons and dispersive shock waves for the (2+1)-dimensional defocusing nonlinear Schrodinger equation / Gross-Pitaevskii (NLS / GP) equation is considered. Special attention is given to the small (shallow) amplitude regime, which limits to the Kadomtsev-Petviashvili (KP) equation. We study analytically and numerically the eigenvalues of the linearized NLS / GP equation. The dispersion relation for shallow solitons is obtained asymptotically beyond the KP limit. This yields 1) the maximum growth rate and associated wavenumber of unstable perturbations; and 2) the separatrix between convective and absolute instabilities. The latter result is used to study the transition between convective and absolute instabilities of oblique dispersive shock waves (DSWs). Stationary and nonstationary oblique DSWs are constructed analytically and investigated numerically by direct simulations of the NLS / GP equation. The instability properties of oblique DSWs are found to be directly related to those of the dark soliton. It is found that stationary and nonstationary oblique DSWs have the same jump conditions in the shallow and hypersonic regimes. These results have application to controlling nonlinear waves in dispersive media.Comment: 34 pages, 15 figure

Risk Perception and Drug Safety Evaluation

The authors present a Risk communication framework based on a survey of empirical research concerning public Risk perceptions. They also apply it to the area of pharmaceutical regulation to suggest more effective regulatory strategies

Capital Account Liberalization and Foreign Direct Investment

We examine the impact of capital account policies on FDI inflows. Using an annual panel dataset of 83 developing and developed countries for 1984-2000, we find that capital account openness is positively but only very moderately associated with the amount of FDI inflows after controlling for other macroeconomic and institutional measures. To a large extent, other country characteristics seem to determine FDI inflows instead of capital account policies. Furthermore, we find that capital controls are easily circumvented in corrupt and politically unstable regimes. We conclude that liberalizing the capital account is not sufficient to generate increases in inflows unless it is accompanied by a lower level of corruption or a decrease in political risk.Foreign direct investment, capital controls, capital flows, capital account liberalization

Interference, Coulomb blockade, and the identification of non-abelian quantum Hall states

We examine the relation between different electronic transport phenomena in a Fabry-Perot interferometer in the fractional quantum Hall regime. In particular, we study the way these phenomena reflect the statistics of quantum Hall quasi-particles. For two series of states we examine, one abelian and one non-abelian, we show that the information that may be obtained from measurements of the lowest order interference pattern in an open Fabry-Perot interferometer is identical to the one that may be obtained from the temperature dependence of Coulomb blockade peaks in a closed interferometer. We argue that despite the similarity between the experimental signatures of the two series of states, interference and Coulomb blockade measurements are likely to be able to distinguish between abelian and non-abelian states, due to the sensitivity of the abelian states to local perturbations, to which the non-abelian states are insensitive.Comment: 10 pages. Published versio

Is Foreign Direct Investment Good for Growth? Evidence from Sectoral Analysis of China and Vietnam

We estimate the impact of FDI on growth using sectoral data for FDI inflows to China and Vietnam. Previous empirical studies, using either cross-country growth regressions or firm-level micro-econometric analysis, fail to reach a consensus. Our paper is the first to use sectoral FDI inflow data to evaluate the sector-specific impact of FDI on growth. Our results show that, for the two developing-transition economies we examine, FDI has a statistically-significant positive effect on economic growth operating directly and through its interaction with labor. Intriguingly, we find the effects seem to be very different across economic sectors, with almost all the beneficial impact limited to industrial sector. Other sectors appear to gain very little growth benefit from sector-specific FDI.Foreign direct investment, growth, China, Vietnam

Coulomb blockade as a probe for non-Abelian statistics in Read-Rezayi states

We consider a quantum dot in the regime of the quantum Hall effect, particularly in Laughlin states and non-Abelian Read-Rezayi states. We find the location of the Coulomb blockade peaks in the conductance as a function of the area of the dot and the magnetic field. When the magnetic field is fixed and the area of the dot is varied, the peaks are equally spaced for the Laughlin states. In contrast, non-Abelian statistics is reflected in modulations of the spacing which depend on the magnetic field.Comment: Published versio

Experimental signatures of non-Abelian statistics in clustered quantum Hall states

We discuss transport experiments for various non-Abelian quantum Hall states, including the Read-Rezayi series and a paired spin singlet state. We analyze the signatures of the unique characters of these states on Coulomb blockaded transport through large quantum dots. We show that the non-Abelian nature of the states manifests itself through modulations in the spacings between Coulomb blockade peaks as a function of the area of the dot. Even though the current flows only along the edge, these modulations vary with the number of quasiholes that are localized in the bulk of the dot. We discuss the effect of relaxation of edge states on the predicted Coulomb blockade patterns, and show that it may suppress the dependence on the number of bulk quasiholes. We predict the form of the lowest order interference term in a Fabry-Perot interferometer for the spin singlet state. The result indicates that this interference term is suppressed for certain values of the quantum numbers of the collective state of the bulk quasiholes, in agreement with previous findings for other clustered states belonging to the Read-Rezayi series.Comment: 19 pages, 4 figures, 2 tables. Published versio

Theory of Magnetodynamics Induced by Spin Torque in Perpendicularly Magnetized Thin Films

A nonlinear model of spin wave excitation using a point contact in a thin ferromagnetic film is introduced. Large-amplitude magnetic solitary waves are computed, which help explain recent spin-torque experiments. Numerical simulations of the fully nonlinear model predict excitation frequencies in excess of 0.2 THz for contact diameters smaller than 6 nm. Simulations also predict a saturation and red shift of the frequency at currents large enough to invert the magnetization under the point contact. The theory is approximated by a cubic complex Ginzburg-Landau type equation. The mode's nonlinear frequency shift is found by use of perturbation techniques, whose results agree with those of direct numerical simulations.Comment: 5 pages, 4 figures, submitted to PR