Policy reform and farmers' wheat allocation in rural China: a case study

Market-oriented policy reforms often have important effects on farm-level grain production and utilisation decisions in developing countries. China’s grain farmers are of particular interest because of China’s importance in world grain markets and because of China’s recent major agricultural policy advances and retrenchments. An empirical evaluation of market liberalisation among farmers located in two provinces in China on farm-level wheat consumption, market sales and on-farm storage during 1994 is presented. The results indicate that policymakers should account for such changes in farm household behaviour in designing and assessing the consequence ofmarket liberalisation programs for agricultural sectors in developing countries.China, grain storage, household allocation decisions, procurement quotas, wheat, Crop Production/Industries,

Ultracold fermions in a one-dimensional bipartite optical lattice: metal-insulator transitions driven by shaking

We describe the behavior of a system of fermionic atoms loaded in a bipartite one-dimensional optical lattice that is under the action of an external time-periodic driving force. By using Floquet theory, an effective model with renormalized hopping coefficients is derived. The insulating behavior characterizing the system at half-filling in the absence of driving is dynamically suppressed and for particular values of the driving parameter the system becomes either a standard metal or an unconventional metal with four Fermi points. We use the bosonization technique to investigate the effect of on-site Hubbard interactions on the four Fermi-point metal-insulator phase transition. Attractive interactions are expected to enlarge the regime of parameters where the unconventional metallic phase arises, whereas repulsive interactions reduce it. This metallic phase is known to be a Luther-Emery liquid (spin gapped metal) for both, repulsive and attractive interactions, contrarily to the usual Hubbard model which exhibits a Mott insulator phase for repulsive interactions. Ultracold fermions in driven one-dimensional bipartite optical lattices provide an interesting platform for the realization of this long studied four Fermi-point unconventional metal.Comment: 11 pages, 6 figure

GOVERNMENT POLICIES AND ON-FARM WHEAT ALLOCATION IN RURAL CHINA

Market-oriented policy reforms have potentially important effects on farm-level grain production and utilization decisions in developing countries. This paper provides an empirical evaluation of the potential effects of market liberalization in China on farm-level wheat consumption, market sales, and on-farm storage. The results indicate that price changes have economically important impacts on utilization decisions by farm families through both income and substitution effects and that off- farm income also appears to be significant. The potential to earn off-farm income is also shown to be an important factor in grain utilization decisions. Storage is affected by government procurement policies as well as by more traditional food and income security considerations. The results indicate that policy makers should account for such changes in farm household behavior in designing and assessing the consequence of market liberalization programs for agricultural sectors in developing countries.China, wheat, grain storage, procurement quotas, household allocation decisions, Agricultural and Food Policy, Q18,

Exploring the international linkages of the euro area: a global VAR analysis

This paper presents a quarterly global model linking individual country vector errorcorrecting models in which the domestic variables are related to the country-specific foreign variables. The global VAR (GVAR) model is estimated for 26 countries, the euro area being treated as a single economy, over the period 1979-2003. It advances research in this area in a number of directions. In particular, it provides a theoretical framework where the GVAR is derived as an approximation to a global unobserved common factor model. It develops a sieve bootstrap procedure for simulation of the GVAR as a whole to test the structural stability of the regression coefficients and error variances, and to establish confidence bounds for the impulse responses. Finally, in addition to generalized impulse responses, the paper also considers the use of the GVAR for "structural" impulse response analysis. JEL Classification: C32, E17, F47Global interdependencies, global macroeconomic modeling, Global VAR (GVAR), impulse responses

Quantum simulation of correlated-hopping models with fermions in optical lattices

By using a modulated magnetic field in a Feshbach resonance for ultracold fermionic atoms in optical lattices, we show that it is possible to engineer a class of models usually referred to as correlated-hopping models. These models differ from the Hubbard model in exhibiting additional density-dependent interaction terms that affect the hopping processes. In addition to the spin-SU(2) symmetry, they also possess a charge-SU(2) symmetry, which opens the possibility of investigating the $\eta$-pairing mechanism for superconductivity introduced by Yang for the Hubbard model. We discuss the known solution of the model in 1D (where $\eta$ states have been found in the degenerate manifold of the ground state) and show that, away from the integrable point, quantum Monte Carlo simulations at half filling predict the emergence of a phase with coexisting incommensurate spin and charge order.Comment: 10 pages, 9 figure

Coupled-resonator-induced transparency with a squeezed vacuum

We present the first experimental observation of quantum fluctuation spectra in two coupled optical cavities with an injected squeezed vacuum light. The quadrature components of the reflected squeezed vacuum spectra are measured by phase sensitive homodyne detector. The experimental results demonstrate coupled-resonator-induced transparency in the quantum regime, in which electromagnetically-induced-transparency-like characteristic of the absorption and dispersion properties of the coupled optical cavities determines the line-shape of the reflected quantum noise spectra.Comment: 4 pages, 4 figures, appear in Phys. Rev. Let

Exploring the International Linkages of the Euro Area: a Global VAR Analysis

This paper presents a global model linking individual country vector error-correcting models in which the domestic variables are related to the country-specific variables as an approximate solution to a global common factor model. This global VAR is estimated for 26 countries, the euro area being treated as a single economy. This paper proposes two important extensions of previous research (see Pesaran, Schuermann and Weiner, 2004). First, it provides a theoretical framework where the GVAR is derived as an approximation to a global unobserved common factor model. Also using average pair-wise cross-section error correlations, the GVAR approach is shown to be quite effective in dealing with the common factor interdependencies and international comovements of business cycles. Second, in addition to generalised impulse response functions, we propose an identification scheme to derive structural impulse responses. We focus on identification of shocks to the US economy, particularly the monetary policy shocks, and consider the time profiles of their effects on the euro area. To this end we include the US model as the first country model and consider alternative orderings of the US variables. Further to the US monetary policy shock, we also consider oil price, US equity and US real output shocks.Global VAR (GVAR), global interdependencies, global macroeconomic modeling, impulse responses

Finite-momentum Bose-Einstein condensates in shaken 2D square optical lattices

We consider ultracold bosons in a 2D square optical lattice described by the Bose-Hubbard model. In addition, an external time-dependent sinusoidal force is applied to the system, which shakes the lattice along one of the diagonals. The effect of the shaking is to renormalize the nearest-neighbor hopping coefficients, which can be arbitrarily reduced, can vanish, or can even change sign, depending on the shaking parameter. It is therefore necessary to account for higher-order hopping terms, which are renormalized differently by the shaking, and introduce anisotropy into the problem. We show that the competition between these different hopping terms leads to finite-momentum condensates, with a momentum that may be tuned via the strength of the shaking. We calculate the boundaries between the Mott-insulator and the different superfluid phases, and present the time-of-flight images expected to be observed experimentally. Our results open up new possibilities for the realization of bosonic analogs of the FFLO phase describing inhomogeneous superconductivity.Comment: 7 pages, 7 figure

Anomalous RR Lyrae stars(?). III. CM Leonis

Time series of B,V,I CCD photometry and radial velocity measurements from high resolution spectroscopy (R=30,000) covering the full pulsation cycle are presented for the field RR Lyrae star CM Leonis. The photometric data span a 6 year interval from 1994 to 1999, and allow us to firmly establish the pulsation mode and periodicity of the variable. The derived period P=0.361699 days (+/- 0.000001) is very close to the value published in the Fourth Edition of the General Catalogue of Variable Stars (P=0.361732 days). However, contrary to what was previously found, the amplitude and shape of the light curve qualify CM Leo as a very regular first overtone pulsator with a prominent hump on the rising branch of its multicolour light curves. According to an abundace analysis performed on three spectra taken near minimum light (0.42 < phase < 0.61), CM Leo is a metal-poor star with metal abundance [Fe/H]=-1.93 +/- 0.20. The photometric and radial velocity curves of CM Leo have been compared with the predictions of suitable pulsational models to infer tight constraints on the stellar mass, effective temperature, and distance modulus of the star. We derive a true distance modulus of CM Leo of (m-M)0=13.11 +/- 0.02 mag and a corresponding absolute magnitude of Mv=0.47 +/- 0.04. This absolute magnitude, once corrected for evolutionary and metallicity effects, leads to a true distance modulus of the Large Magellanic Cloud of (m-M)0=18.43 +/- 0.06 mag, in better agreement with the long astronomical distance scale.Comment: 14 pages, 10 figures, accepted for publication in MNRA