Transport coefficients of multi-particle collision algorithms with velocity-dependent collision rules

Detailed calculations of the transport coefficients of a recently introduced particle-based model for fluid dynamics with a non-ideal equation of state are presented. Excluded volume interactions are modeled by means of biased stochastic multiparticle collisions which depend on the local velocities and densities. Momentum and energy are exactly conserved locally. A general scheme to derive transport coefficients for such biased, velocity dependent collision rules is developed. Analytic expressions for the self-diffusion coefficient and the shear viscosity are obtained, and very good agreement is found with numerical results at small and large mean free paths. The viscosity turns out to be proportional to the square root of temperature, as in a real gas. In addition, the theoretical framework is applied to a two-component version of the model, and expressions for the viscosity and the difference in diffusion of the two species are given.Comment: 31 pages, 8 figures, accepted by J. Phys. Cond. Matte

Structural change in European calf markets: Policy decoupling and movement restrictions

We analyse weekly calf prices from 2003 to 2009 to assess the impact of two important events which changed the structure of European cattle markets. We find the four European calf markets studied to be integrated. The decoupling of farm payments in the framework of the 2003 reforms of the Common Agricultural Policy is found to reduce prices. We ascertain that the outbreak of the Blue Tongue disease induced a structural change in some of the markets. Using counterfactual scenarios, we provide an indication of the effects resulting from granting member states a high degree of discretion in implementation.2003 CAP reform, cattle market, decoupling, European Union, market integration, Agricultural and Food Policy, Farm Management, Land Economics/Use,

Spatial market integration in the EU beef and veal sector: policy decoupling and export bans

The 2003 reforms of the Common Agricultural Policy of the Euro-pean Union allowed for discretionary implementation among member states. Discretion was allowed with respect to the timing and the degree of decoupling of policy support. Differences among member states were particularly apparent in the European beef and veal sector. Using weekly data from 2003 to 2009, we assess the consequences of different national implementation strategies of the reforms on market integration for young calves, which are intensively traded in the European Union. Time series properties are analyzed with a range unit-root test after which a multivariate cointegration model is estimated. We find that the calf markets in Germany, France, the Netherlands and Spain are integrated and tightly interrelated as evidenced by both short and long-run price transmis-sion. We also find strong statistical support for the hypothesis that decoupling reduced calf price levels. Additionally, we ascertain that the outbreak of the Blue Tongue disease induced a structural change in parts of the EU calf market. Using counterfactual scenarios, we provide an indication of the cost involved with granting member states such a high degree of discretion in implementation. We conclude that the national markets studied here belong to a common market. --2003 CAP reform,calf market,decoupling,EU,market integration,price transmission

Slave-boson field fluctuation approach to the extended Falicov-Kimball model: charge, orbital, and excitonic susceptibilities

Based on the SO(2)-invariant slave-boson scheme, the static charge, orbital, and excitonic susceptibilities in the extended Falicov-Kimball model are calculated. Analyzing the phase without long-range order we find instabilities towards charge order, orbital order, and the excitonic insulator (EI) phase. The instability towards the EI is in agreement with the saddle-point phase diagram. We also evaluate the dynamic excitonic susceptibility, which allows the investigation of uncondensed excitons. We find qualitatively different features of the exciton dispersion at the semimetal-EI and at the semiconductor-EI transition supporting a crossover scenario between a BCS-type electron-hole condensation and a Bose-Einstein condensation of preformed bound electron-hole pairs.Comment: 8 pages, 9 figures, final versio

Comment on ``Solidification of a Supercooled Liquid in a Narrow Channel''

Comment on PRL v. 86, p. 5084 (2001) [cond-mat/0101016]. We point out that the authors' simulations are consistent with the known theory of steady-state solutions in this system

Quantum J1J_1--J2J_2 antiferromagnet on the stacked square lattice: Influence of the interlayer coupling on the ground-state magnetic ordering

Using the coupled-cluster method (CCM) and the rotation-invariant Green's function method (RGM), we study the influence of the interlayer coupling $J_\perp$ on the magnetic ordering in the ground state of the spin-1/2 $J_1$-$J_2$ frustrated Heisenberg antiferromagnet ($J_1$-$J_2$ model) on the stacked square lattice. In agreement with known results for the $J_1$-$J_2$ model on the strictly two-dimensional square lattice ($J_\perp=0$) we find that the phases with magnetic long-range order at small $J_2< J_{c_1}$ and large $J_2> J_{c_2}$ are separated by a magnetically disordered (quantum paramagnetic) ground-state phase. Increasing the interlayer coupling $J_\perp>0$ the parameter region of this phase decreases, and, finally, the quantum paramagnetic phase disappears for quite small $J_\perp \sim 0.2 ... 0.3 J_1$.Comment: 4 pages, 3 figure

AUSWIRKUNGEN DER FISCHLER-REFORM UND DER BLAUZUNGENKRANKHEIT AUF DIE EUROPÄISCHEN KÄLBERMÄRKTE

Entkopplung, Europäische Union, Faktormärkte, Fischlerreform, GAP, Kälbermarkt, Marktintegration, Agricultural and Food Policy, Demand and Price Analysis, Research Methods/ Statistical Methods,

Quasiperiodic Tip Splitting in Directional Solidification

We report experimental results on the tip splitting dynamics of seaweed growth in directional solidification of succinonitrile alloys with poly(ethylene oxide) or acetone as solutes. The seaweed or dense branching morphology was selected by solidifying grains which are oriented close to the {111} plane. Despite the random appearance of the growth, a quasiperiodic tip splitting morphology was observed in which the tip alternately splits to the left and to the right. The tip splitting frequency f was found to be related to the growth velocity V as a power law f V^{1.5}. This finding is consistent with the predictions of a tip splitting model that is also presented. Small anisotropies are shown to lead to different kinds of seaweed morphologies.Comment: 4 pages, 7 figures, submitted to Physical Review Letter