Constraints on spin observables

Positivity constrains the allowed domain for sets of spin observables in exclusive or inclusive reactions. Examples are given for strangeness-echange reactions and photoproduction.Comment: 4 pages, to appear in the Proc. QCD08, MOntpellier, France, July 2008, ed. S. Nariso

Spin observables and spin structure functions: inequalities and dynamics

Model-independent identities and inequalities relating the various spin observables of a reaction are reviewed in a unified formalism, together with their implications for dynamical models, their physical interpretation, and the quantum aspects of the information carried by spins, in particular entanglement. These constraints between observables can be obtained from the explicit expression of the observables in terms of a set of amplitudes, a non-trivial algebraic exercise which can be preceded by numerical simulation with randomly chosen amplitudes, from anticommutation relations, or from the requirement that any polarisation vector is less than unity. The most powerful tool is the positivity of the density matrices describing the reaction or its crossed channels, with a projection to single out correlations between two or three observables. For the exclusive reactions, the cases of the strangeness-exchange proton-antiproton scattering and the photoproduction of pseudoscalar mesons are treated in some detail: all triples of observables are constrained, and new results are presented for the allowed domains. The positivity constraints for total cross-sections and single-particle inclusive reactions are reviewed, with application to spin-dependent structure functions and parton distributions. The corresponding inequalities are shown to be preserved by the evolution equations of QCD.Comment: 135 pages, 37 figures, pdflatex, to appear in Physics Reports, new subsections added, typos corrected, references adde

Spin observables in antiproton-proton to AntiLambda-Lambda and density-matrix constraints

The positivity conditions of the spin density matrix constrain the spin observables of the reaction antiproton-proton to AntiLambda-Lambda, leading to model-independent, non-trivial inequalities. The formalism is briefly presented and examples of inequalities are provided.Comment: 4 pages, Latex with included AIP style, Contribution to LEAP 05, to appear in the Proceeding

Model-independent constraints on spin observables

We discuss model-independent constraints on spin observables in exclusive and inclusive reactions, with special attention to the case of photoproduction.Comment: 6 pages, 5 figures, Talk by J.-M. Richard at NSTAR 2009, IHEP, Beijing (China), April 19-22, 2009, Proc. to appear in "Chinese Physics C

Constraints on spin observables in antiproton-proton to antiLambda-Lambda

It is recalled that spin-observables in the strangeness-exchange reaction $\bar{p}{p} \to \bar{\Lambda}{\Lambda}$ are not independent but are related to each other by simple algebraic relations. This provides constraints on the existing data on polarization and spin-correlation coefficients, and also on the forthcoming data obtained using a polarized proton target.Comment: RevTex, 9 page

Structural, electronic and magnetic properties of Ru2CrGe and Ru2MnGe: FP-LAPW calculations

Structural and magnetic properties as well as the electronic structures of [Formula: see text] Heusler alloys were investigated in the framework of first principle calculation. Using the full-potential linearized augmented plane wave (FP-LAPW) in connection with the generalized gradient approximation (GGA) treatment of exchange-correlation energy, we have performed the structural optimization in the non-magnetic (NM) and three different magnetic configurations: FM, AFM-I and AFM-II. We have found that our two compounds are stable for the AFM-II state, which agree with the available experimental and theoretical results. The exchange constants [Formula: see text] and [Formula: see text] as well as the temperature of transition to the paramagnetic state [Formula: see text] were estimated here by the use of the energy difference method and the mean field approximation. The electronic structure of our compounds in their magnetic state was also studied. The GGA [Formula: see text]+ [Formula: see text]U method has also been used to take into account the strong correlations among the d orbitals of [Formula: see text] and [Formula: see text] atoms. This has considerably improved both the electronic and magnetic results which became close to the corresponding experimental data. We have finally studied the thermodynamic properties using the quasi-harmonic Debye model as implemented in the Gibbs Program. </jats:p

Eddy Current Microsensor Dedicated to the Nondestructive Testing of Conductive Plates

To ensure the safety of transportation and prevent accidents, nondestructive testing by Eddy current (EC) is proposed to check the conditions of industrial parts. EC sensors are used for the inspection of defects in conductive parts using coil fed by alternative current. These sensors are sensitive to defects, easy to implement, and robust for industrial applications. In order to satisfy the requirement for both reliability and speed during inspection operations, innovative EC sensors that can provide higher sensitivity, better spatial resolution, and more information about the defect characteristics, such as microsensors, are developed. The miniaturization of these sensors’ coils conforms the sensor for micro-defects in critical parts and in complex materials. In this paper, a microsensor dedicated to EC application is studied and characterized to identify the coil parameters and to optimize the geometry of the probe. An approach for the modeling of microsensor dedicated to EC nondestructive applications is proposed. The moving band finite element method is implemented for this purpose to take into account the movement of the sensor and to simplify the modeling of EC testing configurations that use this kind ofsensor. Experimental validations were conducted on a nickel-based alloy specimen. The real and imaginary parts of the impedance at every position of the sensor computed by experiments and simulations were consistent with each other. Simulation results proved that the sensor was capable of detecting micro-defects with a size starting from 0.1 mm under the optimal excitation frequency of 0.8 MHz. It is not only sensitive to micro-cracks, but also it distinguishes the different crack sizes (length, width, anddepth).</jats:p