1,426 research outputs found
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 -- 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
on the magnetic ordering in the ground state of the spin-1/2
- frustrated Heisenberg antiferromagnet (- model) on the
stacked square lattice. In agreement with known results for the -
model on the strictly two-dimensional square lattice () we find that
the phases with magnetic long-range order at small and large
are separated by a magnetically disordered (quantum
paramagnetic) ground-state phase. Increasing the interlayer coupling
the parameter region of this phase decreases, and, finally, the
quantum paramagnetic phase disappears for quite small .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
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