Currency crises and uncertainty about fundamentals

This paper extends some theoretical results of Morris and Shin (1998) concerning the role of uncertainty about fundamentals in currency crises and tests their empirical relevance using a novel approach based on the distribution of survey expectations. Econometric evidence from the Asian crisis confirms the prediction that the dispersion of expectations affects the probability of a speculative attack and that the sign of this effect depends on whether expected fundamentals are "good" or "bad". Extensive robustness checks support the findings.speculative attack, exchange rate crisis, public and private information

What is the Most Effective Monetary Policy for Aid-Receiving Countries?

This paper analyses how monetary policy can enhance the effectiveness of volatile aid fl ows. We find that monetary policy is effective in reducing trade balance volatility. We propose the following taxonomy, excluding the case of emergency assistance. Monetary policy should slow down consumption growth and build up international reserves when aid is abundant and deplete them to finance imports and support consumption when aid is scarce. If foreign aid also affects productivity growth, monetary policy should take this productivity effect into account in responding to aid flows.Aid effectiveness, monetary policy, real exchange rate, Dutch disease

Signaling Fiscal Regime Sustainability

This paper proposes a signaling model of fiscal stabilizations that offers a new perspective on why governments deviate from optimal tax smoothing. In our model, dependable - but not fully credible - governments have an incentive to tighten the fiscal regime when the signaling effect on credit ratings is larger (that is, when a sufficiently large stock of debt has been accumulated). At this point, they may deviate from tax smoothing in order to avoid being mimicked by weak governments. We show that a testable prediction of our model is that primary balances and debt stocks are complementary inputs in the credit rating function and we successfully test it on Irish, Belgian, and Danish data from the late 1970s to the early 1990s.fiscal policy, taxation, debt, credit, economic models

Aid, Exports, and Growth: A Time-Series Perspective on the Dutch Disease Hypothesis

The available evidence on the effects of aid on growth is notoriously mixed. We use a novel empirical methodology, a heterogeneous panel vector-autoregression model identified through factor analysis, to study the dynamic response of exports, imports, and per capita GDP growth to a "global" aid shock (the common component of individual country aid-to-GDP ratios). We find that the estimated cumulative resposive of exports and per capita GDP growth to a global aid shock are strongly positively correlated, and both responses are inversely related to exchange rate overvaluation measures. We interpret this evidence as consistent with the Dutch disease hypothesis. However, we also find that, in countries with less overvalued real exchange rates, exports and per capita GDP growth respond positively to a global aid shock. This evidence suggests that preventing exchange rate overvaluations may allow aid-receiving countries to avoid the Dutch disease.Aid, Common factors, Dutch Disease, Growth Panel VARs, Exchange rate overvaluation

Extrinsic electromagnetic chirality in all-photodesigned one-dimensional THz metamaterials

We suggest that all-photodesigned metamaterials, sub-wavelength custom patterns of photo-excited carriers on a semiconductor, can display an exotic extrinsic electromagnetic chirality in terahertz (THz) frequency range. We consider a photo-induced pattern exhibiting 1D geometrical chirality, i.e. its mirror image can not be superposed onto itself by translations without rotations and, in the long wavelength limit, we evaluate its bianisotropic response. The photo-induced extrinsic chirality turns out to be fully reconfigurable by recasting the optical illumination which supports the photo-excited carriers. The all-photodesigning technique represents a feasible, easy and powerful method for achieving effective matter functionalization and, combined with the chiral asymmetry, it could be the platform for a new generation of reconfigurable devices for THz wave polarization manipulation.Comment: 11 page

Terahertz optically tunable dielectric metamaterials without microfabrication

We theoretically investigate the terahertz dielectric response of a semiconductor slab hosting an infrared photoinduced grating. The periodic structure is due to the charge carries photo-excited by the interference of two tilted infrared plane waves so that the grating depth and period can be tuned by modifying the beam intensities and incidence angles, respectively. In the case where the grating period is much smaller than the terahertz wavelength, we numerically evaluate the ordinary and extraordinary component of the effective permittivity tensor by resorting to electromagnetic full-wave simulation coupled to the dynamics of charge carries excited by infrared radiation. We show that the photoinduced metamaterial optical response can be tailored by varying the grating and it ranges from birefringent to hyperbolic to anisotropic negative dielectric without resorting to microfabrication.Comment: 3 pages, 2 figure

Microwave Irradiation Effects on Random Telegraph Signal in a MOSFET

We report on the change of the characteristic times of the random telegraph signal (RTS) in a MOSFET operated under microwave irradiation up to 40 GHz as the microwave field power is raised. The effect is explained by considering the time dependency of the transition probabilities due to a harmonic voltage generated by the microwave field that couples with the wires connecting the MOSFET. From the dc current excited into the MOSFET by the microwave field we determine the corresponding equivalent drain voltage. The RTS experimental data are in agreement with the prediction obtained with the model, making use of the voltage data measured with the independent dc microwave induced current. We conclude that when operating a MOSFET under microwave irradiation, as in single spin resonance detection, one has to pay attention into the effects related to microwave irradiation dependent RTS changes.Comment: 3 pages, 4 figure

Reconfigurable photoinduced metamaterials in the microwave regime

We investigate optically reconfigurable dielectric metamaterials at gigahertz frequencies. More precisely, we study the microwave response of a subwavelength grating optically imprinted into a semiconductor slab. In the homogenized regime, we analytically evaluate the ordinary and extraordinary component of the effective permittivity tensor by taking into account the photo-carrier dynamics described by the ambipolar diffusion equation. We analyze the impact of semiconductor parameters on the gigahertz metamaterial response which turns out to be highly reconfigurable by varying the photogenerated grating and which can show a marked anisotropic behavior.Comment: 6 figures, 7 page

Higher-Order Permanent Scatterers Analysis

The permanent scatterers (PS) technique is a multi-interferogram algorithm for DInSAR analyses developed in the late nineties to overcome the difficulties related to the conventional approach, namely, phase decorrelation and atmospheric effects. The successful application of this technology to many geophysical studies is now pushing toward further improvements and optimizations. A possible strategy to increase the number of radar targets that can be exploited for surface deformation monitoring is the adoption of parametric super-resolution algorithms that can cope with multiple scattering centres within the same resolution cell. In fact, since a PS is usually modelled as a single pointwise scatterer dominating the background clutter, radar targets having cross-range dimension exceeding a few meters can be lost (at least in C-band datasets), due to geometrical decorrelation phenomena induced in the high normal baseline interferograms of the dataset. In this paper, the mathematical framework related to higher-order SAR interferometry is presented as well as preliminary results obtained on simulated and real data. It is shown how the PS density can be increased at the price of a higher computational load