Stability of an upwind Petrov Galerkin discretization of convection diffusion equations

We study a numerical method for convection diffusion equations, in the regime of small viscosity. It can be described as an exponentially fitted conforming Petrov-Galerkin method. We identify norms for which we have both continuity and an inf-sup condition, which are uniform in mesh-width and viscosity, up to a logarithm, as long as the viscosity is smaller than the mesh-width or the crosswind diffusion is smaller than the streamline diffusion. The analysis allows for the formation of a boundary layer.Comment: v1: 18 pages. 2 figures. v2: 22 pages. Numerous details added and completely rewritten final proof. 8 pages appendix with old proo

Bogoliubov theory of entanglement in a Bose-Einstein condensate

We consider a Bose-Einstein condensate which is illuminated by a short resonant light pulse that coherently couples two internal states of the atoms. We show that the subsequent time evolution prepares the atoms in an interesting entangled state called a spin squeezed state. This evolution is analysed in detail by developing a Bogoliubov theory which describes the entanglement of the atoms. Our calculation is a consistent expansion in $1/\sqrt{N}$, where $N$ is the number of particles in the condensate, and our theory predict that it is possible to produce spin squeezing by at least a factor of $1/\sqrt{N}$. Within the Bogoliubov approximation this result is independent of temperature.Comment: 14 pages, including 5 figures, minor changes in the presentatio

BIOMECHANICAL PROFILE OF SOCCER GOALKEEPERS

Although the soccer goalkeeper often plays a decisive role in the outcome of a match, research on the goalkeeper’s actions or the qualities required of a top class goalkeeper is scarce. With this study we attempted to define a biomechanical profile of the goalkeeper. We tested whether the skill level of 6 goalkeepers, determined by the league they played in, correlated with a number of biomechanical tests. The tests were devised as standardized measurements of typical goalkeeper actions; they comprised various jumps, a short sprint and a leg strength measurement. We found no correlation between the goalkeepers’ skill level and their score in any of the tests. Thus, with reservation for the limited number of subjects, we conclude that the measured biomechanical parameters are of minor importance compared to skills as tactical understanding, perception and anticipation

Quantification of Salmonella and Yersinia on pork carcasses by simulation modelling

Stagnation in the success of control programmes in pig production in Denmark has led to an increased interest in the development of alternative control strategies such as decontamination of carcasses to further decrease the attribution of pork meat to human foodborne illness. This project sets out to develop a model for quantitative estimation of slaughterhouse output of Salmonella and Yersinia . Distributions of the occurrence of Salmonefla, Yersinia and E. coli on pork carcasses are based on the analysis of paired faecal samples and carcass swabs from 2880 animals originating from four abattoirs. By combining the estimated quantity of faecal contamination of carcasses with a semi-quantitative distribution of the number of Safmoneffa or Yersinia per gram faeces, an output distribution describing the number of Salmonella or Yersinia bacteria per carcass can be established. In order to validate the model, carcass swabs, analysed for Salmonefla and Yersinia serve as control. After the model has been validated, the effect of various decontamination methods on human exposure to foodborne pathogens in pork will be evaluated in both economic terms as well as with regard to public health impact

Spin Squeezing in the Ising Model

We analyze the collective spin noise in interacting spin systems. General expressions are derived for the short time behaviour of spin systems with general spin-spin interactions, and we suggest optimum experimental conditions for the detection of spin squeezing. For Ising models with site dependent nearest neighbour interactions general expressions are presented for the spin squeezing parameter for all times. The reduction of collective spin noise can be used to verify the entangling powers of quantum computer architectures based on interacting spins.Comment: 7 pages, including 3 figure

Structure of boson systems beyond the mean-field

We investigate systems of identical bosons with the focus on two-body correlations. We use the hyperspherical adiabatic method and a decomposition of the wave function in two-body amplitudes. An analytic parametrization is used for the adiabatic effective radial potential. We discuss the structure of a condensate for arbitrary scattering length. Stability and time scales for various decay processes are estimated. The previously predicted Efimov-like states are found to be very narrow. We discuss the validity conditions and formal connections between the zero- and finite-range mean-field approximations, Faddeev-Yakubovskii formulation, Jastrow ansatz, and the present method. We compare numerical results from present work with mean-field calculations and discuss qualitatively the connection with measurements.Comment: 26 pages, 6 figures, submitted to J. Phys. B. Ver. 2 is 28 pages with modified figures and discussion

Entanglement and Extreme Spin Squeezing

For any mean value of a cartesian component of a spin vector we identify the smallest possible uncertainty in any of the orthogonal components. The corresponding states are optimal for spectroscopy and atomic clocks. We show that the results for different spin J can be used to identify entanglement and to quantity the depth of entanglement in systems with many particles. With the procedure developed in this letter, collective spin measurements on an ensemble of particles can be used as an experimental proof of multi-particle entanglementComment: 4 pages, 2 figures, minor changes in the presentatio