2,703 research outputs found

    PROJECT FOR THE ANALYSIS OF LAND TENURE AND AGRICULTURAL PRODUCTIVITY IN THE REPUBLIC OF MACEDONIA

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    The paper arises out of the Land Market Project and covers detailed data at the individual farm level and in-depth analyses of legal and historical processes. The agricultural sector in Macedonia is characterized by two very different farm enterprise types: small family farms operating on privately owned land, and large socially owned farms. About 30 percent of the total arable land in Macedonia belongs to socially owned farms. Most of the balance belong to the private farm sector; the cooperative sector occupies a small percentage of the arable land. The Land Markets Project addressed five tasks during the six-month term of the project: (1) assess the appropriateness of legislation, regulations, and institutions affecting land tenure and land use, (2) document and assess the land-related constraints to increased productivity and profitability of private farms, (3) document and assess the land-related constraints to increased productivity and profitability of socially owned farms, (4) propose land policy adjustments that would promote increased productivity and profitability of the agricultural sector, (5) identify financial and technical assistance to support the development of land markets that promote efficient, sustainable, and equitable increases in agricultural incomes. This paper reports the results of the first three tasks and then presents a comparative review of the land tenure and productivity results for both the private and the social sector. This comparison forms a basis for policy dialogue. The paper also includes a comprehensive discussion of the policy recommendations that stem from the Land Markets Project.Land tenure--Macedonia (Republic), Land use, Rural--Economic aspects--Macedonia (Republic), Farms, Size of--Macedonia (Republic), Agriculture--Economic aspects--Macedonia (Republic), Agricultural productivity--Macedonia (Republic), Land markets--Macedonia (Republic), Agrarian structure--Macedonia (Republic), Land Economics/Use, Productivity Analysis,

    AGRARIAN REFORM IN UZBEKISTAN AND OTHER CENTRAL ASIAN COUNTRIES

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    The five Central Asian countries that gained their independence at the breakup of the Soviet Union in 1991 have followed different paths of transition to a market economy in the agricultural sector. Kyrgyzstan has been the most aggressive in restructuring agricultural enterprises, privatizing land, and promoting individual farming. Kazakstan and Turkmenistan have had similar legal and policy reforms, but implementation has lagged. Tajikistan's efforts at reform have been hampered by civil strife and continued weakness of government. Uzbekistan, in contrast to the others, has attempted to control its progress towards market-oriented agriculture very closely, with the result that the agrarian sector looks on the surface very similar today to what it looked like in 1991. After a brief discussion of the similarities and differences among the Central Asian countries, this essay explores the results of Uzbekistan's choice to proceed "step by step," as the government says, by examining the country's characteristics of agrarian structure, agricultural production, and policy concerns.Land reform -- Uzbekistan, Land reform -- Asia, Central, Agriculture and state -- Uzbekistan, Agriculture -- Economic aspects -- Uzbekistan, Agrarian structure (Post-reform) -- Uzbekistan, Privatization -- Uzbekistan, Agricultural and Food Policy,

    Light-cone-like spreading of correlations in a quantum many-body system

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    How fast can correlations spread in a quantum many-body system? Based on the seminal work by Lieb and Robinson, it has recently been shown that several interacting many-body systems exhibit an effective light cone that bounds the propagation speed of correlations. The existence of such a "speed of light" has profound implications for condensed matter physics and quantum information, but has never been observed experimentally. Here we report on the time-resolved detection of propagating correlations in an interacting quantum many-body system. By quenching a one-dimensional quantum gas in an optical lattice, we reveal how quasiparticle pairs transport correlations with a finite velocity across the system, resulting in an effective light cone for the quantum dynamics. Our results open important perspectives for understanding relaxation of closed quantum systems far from equilibrium as well as for engineering efficient quantum channels necessary for fast quantum computations.Comment: 7 pages, 5 figures, 2 table

    Running mass of the rho0 meson's implication for the dilepton mass spectrum and the mu+mu-/e+e- branching ratio in the K+ --> pi+l+l- decays

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    We make an attempt to resolve the discrepancy of the observed e+e- mass spectrum in the K+ --> pi+e+e- decay with that predicted by meson dominance. To this end we investigate the properties of the rho0 propagator. We use dispersion relations to evaluate the running mass squared m_rho^2(t) of the rho0 resonance without adjustable parameters. To improve the convergence of the dispersion integral, the momentum dependence of strong vertices is taken from the flux-tube-breaking model of Kokoski and Isgur. The obtained behavior of m_rho^2(t) at small momentum squared t makes the K+ --> pi+e+e- form factor rise faster with increasing tt than in the original meson-dominance calculation and more in agreement with the published data. As a consequence, the meson-dominance prediction of the mu+mu-/e+e- branching ratio changes slightly, from 0.224 to 0.236. We do not see any possibility to accommodate into the meson-dominance approach an even steeper e+e- spectrum, indicated by the preliminary data of the E865 collaboration at BNL AGS.Comment: 13 pages, RevTeX, epsf.sty, 4 embedded figure

    Strong Decays of Light Vector Mesons

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    The vector meson strong decays rho-->pi pi, phi-->KK, and K^star-->pi K are studied within a covariant approach based on the ladder-rainbow truncation of the QCD Dyson--Schwinger equation for the quark propagator and the Bethe--Salpeter equation for the mesons. The model preserves the one-loop behavior of QCD in the ultraviolet, has two infrared parameters, and implements quark confinement and dynamical chiral symmetry breaking. The 3-point decay amplitudes are described in impulse approximation. The Bethe--Salpeter study motivates a method for estimating the masses for heavier mesons within this model without continuing the propagators into the complex plane. We test the accuracy via the rho, phi and K^{star} masses and then produce estimates of the model results for the a_1 and b_1 masses as well as the mass of the proposed exotic vector pi_1(1400).Comment: Submitted for publication; 10x2-column pages, REVTEX 4, 3 .eps files making 3fig

    The Quark-Photon Vertex and the Pion Charge Radius

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    The rainbow truncation of the quark Dyson-Schwinger equation is combined with the ladder Bethe-Salpeter equation for the dressed quark-photon vertex to study the low-momentum behavior of the pion electromagnetic form factor. With model gluon parameters previously fixed by the pion mass and decay constant, the pion charge radius rπr_\pi is found to be in excellent agreement with the data. When the often-used Ball-Chiu Ansatz is used to construct the quark-photon vertex directly from the quark propagator, less than half of rπ2r_\pi^2 is generated. The remainder of rπ2r^2_\pi is seen to be attributable to the presence of the ρ\rho-pole in the solution of the ladder Bethe-Salpeter equation.Comment: 21 pages, 9 figure

    Driven Tunneling Dynamics: Bloch-Redfield Theory versus Path Integral Approach

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    In the regime of weak bath coupling and low temperature we demonstrate numerically for the spin-boson dynamics the equivalence between two widely used but seemingly different roads of approximation, namely the path integral approach and the Bloch-Redfield theory. The excellent agreement between these two methods is corroborated by a novel efficient analytical high-frequency approach: it well approximates the decay of quantum coherence via a series of damped coherent oscillations. Moreover, a suitably tuned control field can selectively enhance or suppress quantum coherence.Comment: 4 pages including 3 figures, submitted for publicatio

    The π\pi, K+K^+, and K0K^0 electromagnetic form factors

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    The rainbow truncation of the quark Dyson-Schwinger equation is combined with the ladder Bethe-Salpeter equation for the meson amplitudes and the dressed quark-photon vertex in a self-consistent Poincar\'e-invariant study of the pion and kaon electromagnetic form factors in impulse approximation. We demonstrate explicitly that the current is conserved in this approach and that the obtained results are independent of the momentum partitioning in the Bethe-Salpeter amplitudes. With model gluon parameters previously fixed by the condensate, the pion mass and decay constant, and the kaon mass, the charge radii and spacelike form factors are found to be in good agreement with the experimental data.Comment: 8 pages, 6 figures, Revte

    Designing spin-1 lattice models using polar molecules

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    We describe how to design a large class of always on spin-1 interactions between polar molecules trapped in an optical lattice. The spin degrees of freedom correspond to the hyperfine levels of a ro-vibrational ground state molecule. Interactions are induced using a microwave field to mix ground states in one hyperfine manifold with the spin entangled dipole-dipole coupled excited states. Using multiple fields anistropic models in one, two, or three dimensions, can be built with tunable spatial range. An illustrative example in one dimension is the generalized Haldane model, which at a specific parameter has a gapped valence bond solid ground state. The interaction strengths are large compared to decoherence rates and should allow for probing the rich phase structure of strongly correlated systems, including dimerized and gapped phases.Comment: 24 pages, 5 figure

    Nuclear Inelastic X-Ray Scattering of FeO to 48 GPa

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    The partial density of vibrational states has been measured for Fe in compressed FeO (w\"ustite) using nuclear resonant inelastic x-ray scattering. Substantial changes have been observed in the overall shape of the density of states close to the magnetic transiton around 20 GPa from the paramagnetic (low pressure) to the antiferromagnetic (high pressure) state. Our data indicate a substantial softening of the aggregate sound velocities far below the transition, starting between 5 and 10 GPa. This is consistent with recent radial x-ray diffraction measurements of the elastic constants in FeO. The results indicate that strong magnetoelastic coupling in FeO is the driving force behind the changes in the phonon spectrum of FeO.Comment: 4 pages, 4 figure
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