An alternative to the Allen-Cahn phase field model for interfaces in solids - numerical efficiency

The derivation of the Allen-Cahn and Cahn-Hilliard equations is based on the Clausius-Duhem inequality. This is not a derivation in the strict sense of the word, since other phase field equations can be fomulated satisfying this inequality. Motivated by the form of sharp interface problems, we formulate such an alternative equation and compare the properties of the models for the evolution of phase interfaces in solids, which consist of the elasticity equations and the Allen-Cahn equation or the alternative equation. We find that numerical simulations of phase interfaces with small interface energy based on the alternative model are more effective then simulations based on the Allen-Cahn model.Comment: arXiv admin note: text overlap with arXiv:1505.0544

A systematic study of two particle correlations from NA49 at CERN SPS

A systematic study of two particle correlations measured by the NA49 experiment is summarized. Radii from Bose Einstein interferometry have been determined separately in different parts of phase space, for different collision systems and at different incident beam energies. Moreover, first results of a new method of accessing space-time asymmetries in the emission of particles by means of non identical particle correlations are presented.Comment: 4 pages 3 figures publ. in proc. of QM99, Torino It Nuclear Physics

Entanglement and the linearity of quantum mechanics

Optimal universal entanglement processes are discussed which entangle two quantum systems in an optimal way for all possible initial states. It is demonstrated that the linear character of quantum theory which enforces the peaceful coexistence of quantum mechanics and relativity imposes severe restrictions on the structure of the resulting optimally entangled states. Depending on the dimension of the one-particle Hilbert space such a universal process generates either a pure Bell state or mixed entangled states. In the limit of very large dimensions of the one-particle Hilbert space the von-Neumann entropy of the optimally entangled state differs from the one of the maximally mixed two-particle state by one bit only.Comment: Proceedings of the X International Symposium on Theoretical Electrical Engineering, ISTET 99, Magdebur

Destruction of quantum coherence and wave packet dynamic

The main aim of this article is to discuss characteristic physical phenomena which govern the destruction of quantum coherence of material wave packets.Comment: to be published in `The Physics and Chemistry of Wave Packets', edited by J. A. Yeazell and T. Uzer (Wiley, N. Y.

Where Turkey stands in Europe and why it should be admitted to the EU

Turkeys position relative to Europe is analyzed from three different perspectives, i.e (i) the semi-official perspective of the Copenhagen criteria, the Maastricht criteria and the Lisbon strategy, (ii) the perspective of comparative surveys, and (iii) the perspective of key European worries regarding future strains on cohesion funds and the complex relationship of the Turkish population to European values. It is shown that Turkeys standing in international comparisons of good governance has been improving in recent years and that the country is on a path of convergence with the Maastricht criteria. Turkey falls considerably short, however, of the employment and education goals of the Lisbon agenda. Comparative surveys show the Turkish population to have not only a low standard of living, but also a very low level of satisfaction with life and with public services, to have comparatively little trust in other people and a low level of civic engagement, and to nourish traditional attitudes concerning religious beliefs, womens rights and gender roles. Since Turkeys admission to the EU would enlarge the EU population by 15 %, but economic output by less than 3 %, Turkeys accession would severely strain EU cohesion funds. Despite these reservations, Turkeys admission to the Union is here advocated for three reasons: (1) Risks of a fundamentalist backlash against Europe would considerably increase if the long-standing accession promise were not kept. (2) Given that the country is entering a very favourable demographic phase for about 2-3 decades, there is considerable economic opportunity with a vast growth potential. (3) Since the recent Eastern enlargements have already decided the debate between federalists and inter-governmentalists in favour of the latter, Europe has more to gain than to lose from Turkeys membership which would strengthen the countrys ties to the West, and provide a chance of proving to the world that the motto of the European Union united in diversity is a better model for the future of international relations than the scenario of a clash of civilizations. --

Renormalization Group Analysis of a Confined, Interacting Bose Gas

The renormalization group is not only a powerful method for describing universal properties of phase transitions but it is also useful for evaluating non- universal properties beyond mean-field theory. In this contribution we concentrate on these latter aspects of the renormalization group approach. We introduce its main underlying ideas in the familiar context of the ideal Bose gas and then apply them to the case of an interacting, confined Bose gas within the framework of the random phase approximation. We model confinement by periodic boundary conditions and demonstrate how confinement modifies the flow equations of the renormalization group changing thus the thermodynamic properties of the gas.Comment: 24 pages, 5 figure

Charged particle production in proton-, deuteron-, oxygen- and sulphur-nucleus collisions at 200 GeV per nucleon

The transverse momentum and rapidity distributions of net protons and negatively charged hadrons have been measured for minimum bias proton-nucleus and deuteron-gold interactions, as well as central oxygen-gold and sulphur-nucleus collisions at 200 GeV per nucleon. The rapidity density of net protons at midrapidity in central nucleus-nucleus collisions increases both with target mass for sulphur projectiles and with the projectile mass for a gold target. The shape of the rapidity distributions of net protons forward of midrapidity for d+Au and central S+Au collisions is similar. The average rapidity loss is larger than 2 units of rapidity for reactions with the gold target. The transverse momentum spectra of net protons for all reactions can be described by a thermal distribution with temperatures' between 145 +- 11 MeV (p+S interactions) and 244 +- 43 MeV (central S+Au collisions). The multiplicity of negatively charged hadrons increases with the mass of the colliding system. The shape of the transverse momentum spectra of negatively charged hadrons changes from minimum bias p+p and p+S interactions to p+Au and central nucleus-nucleus collisions. The mean transverse momentum is almost constant in the vicinity of midrapidity and shows little variation with the target and projectile masses. The average number of produced negatively charged hadrons per participant baryon increases slightly from p+p, p+A to central S+S,Ag collisions

A new Coulomb correction method for Bose-Einstein correlations, based on the Pi+ Pi- correlation measurements

We present the measured correlation functions for pi+ pi-, pi- pi- and pi+ pi+ pairs in central S+Ag collisions at 200 GeV per nucleon. The Gamov function, which has been traditionally used to correct the correlation functions of charged pions for the Coulomb interaction, is found to be inconsistent with all measured correlation functions. Certain problems which have been dominating the systematic uncertainty of the correlation analysis are related to this inconsistency. It is demonstrated that a new Coulomb correction method, based exclusively on the measured correlation function for pi+ pi- pairs, may solve the problem