A microscopic model for Josephson currents

A microscopic model of a Josephson junction between two superconducting plates is proposed and analysed. For this model, the nonequilibrium steady state of the total system is explicitly constructed and its properties are analysed. In particular, the Josephson current is rigorously computed as a function of the phase difference of the two plates and the typical properties of the Josephson current are recovered

BEC for a Coupled Two-type Hard Core Bosons Model

We study a solvable model of two types hard core Bose particles. A complete analysis is given of its equilibrium states including the proof of existence of Bose-Einstein condensation. The plasmon frequencies and the quantum normal modes corresponding to these frequencies are rigorously constructed. In particular we show a two-fold degeneracy of these frequencies. We show that all this results from spontaneous gauge symmetry breakdown

Self-consistent equation for an interacting Bose gas

We consider interacting Bose gas in thermal equilibrium assuming a positive and bounded pair potential $V(r)$ such that 0<\int d\br V(r) = a<\infty. Expressing the partition function by the Feynman-Kac functional integral yields a classical-like polymer representation of the quantum gas. With Mayer graph summation techniques, we demonstrate the existence of a self-consistent relation $\rho (\mu)=F(\mu-a\rho(\mu))$ between the density $\rho$ and the chemical potential $\mu$, valid in the range of convergence of Mayer series. The function $F$ is equal to the sum of all rooted multiply connected graphs. Using Kac's scaling V_{\gamma}(\br)=\gamma^{3}V(\gamma r) we prove that in the mean-field limit $\gamma\to 0$ only tree diagrams contribute and function $F$ reduces to the free gas density. We also investigate how to extend the validity of the self-consistent relation beyond the convergence radius of Mayer series (vicinity of Bose-Einstein condensation) and study dominant corrections to mean field. At lowest order, the form of function $F$ is shown to depend on single polymer partition function for which we derive lower and upper bounds and on the resummation of ring diagrams which can be analytically performed.Comment: 33 pages, 6 figures, submitted to Phys.Rev.

Influence of Surface Conditions on Wear and Friction of Hardmetals

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From research to farm : ex ante evaluation of strategic deworming in pig finishing

This paper upgrades generic and partial information from parasitological research for farm-specific decision support, using two methods from managerial sciences: partial budgeting and frontier analysis. The analysis focuses on strategic deworming in pig finishing and assesses both effects on economic performance and nutrient efficiency. The application of partial budgeting and frontier analysis is based on a production-theoretical system analysis which is necessary to integrate parasitological research results to assess aggregate economic and environmental impacts. Results show that both statistically significant and insignificant parasitological research results have to be taken into account. Partial budgeting and frontier analysis appear to be complementary methods: partial budgeting yields more discriminatory and communicative results, while frontier methods provide additional diagnostics through exploring optimization possibilities and economic-environmental trade-offs. Strategic deworming results in a win-win effect on economic and environmental performances. Gross margin increases with 3 to 12 € per average present finisher per year, depending on the cyclic pig price conditions. The impact on the nutrient balance ranges from +0.2 to –0.5 kg nitrogen per average present finisher per year. The observed efficiency improvements are mainly technical and further economic and environmental optimizations can be achieved through input re-allocation. A user-friendly spreadsheet is provided to translate the generic experimental information to farm-specific conditions