Disorder Averaging and Finite Size Scaling

We propose a new picture of the renormalization group (RG) approach in the presence of disorder, which considers the RG trajectories of each random sample (realization) separately instead of the usual renormalization of the averaged free energy. The main consequence of the theory is that the average over randomness has to be taken after finding the critical point of each realization. To demonstrate these concepts, we study the finite-size scaling properties of the two-dimensional random-bond Ising model. We find that most of the previously observed finite-size corrections are due to the sample-to-sample fluctuation of the critical temperature and scaling is more adequate in terms of the new scaling variables.Comment: 4 pages, 6 figures include

The Effects of Explicit and Implicit Interaction on User Experiences in a Mixed Reality Installation: The Synthetic Oracle

Virtual and mixed reality environments (VMRE) often imply full-body human-computer interaction scenarios. We used a public multimodal mixed reality installation, the Synthetic Oracle, and a between-groups design to study the effects of implicit (e.g., passively walking) or explicit (e.g., pointing) interaction modes on the users' emotional and engagement experiences, and we assessed it using questionnaires. Additionally, real-time arm motion data was used to categorize the user behavior and to provide interaction possibilities for the explicit interaction group. The results show that the online behavior classification corresponded well to the users' interaction mode. In addition, contrary to the explicit interaction, the engagement ratings from implicit users were positively correlated with a valence but were uncorrelated with arousal ratings. Interestingly, arousal levels were correlated with different behaviors displayed by the visitors depending on the interaction mode. Hence, this study confirms that the activity level and behavior of users modulates their experience, and that in turn, the interaction mode modulates their behavior. Thus, these results show the importance of the selected interaction mode when designing users' experiences in VMRE

Tenacibaculum adriaticum sp. nov., from bryozoans in the Adriatic Sea

A rod-shaped, translucent yellow-pigmented, Gram-negative bacterium, strain B390(T), was isolated from the bryozoan Schizobrachiella sanguinea collected in the Adriatic Sea, near Rovinj, Croatia. 16S rRNA gene sequence analysis indicated affiliation to the genus Tenacibaculum, with sequence similarity levels of 94.8-97.3 % to type strains of species with validly published names. It grew at 5-34 degrees C, with optimal growth at 18-26 degrees C, and only in the presence of NaCl or sea salts. In contrast to other type strains of the genus, strain B390(T) was able to hydrolyse aesculin. The predominant menaquinone was MK-6 and major fatty acids were iso-C-15:0, iso-C-15:0 3-OH and iSO-C-15:1. The DNA G + C content was 31.6 mol%. DNA-DNA hybridization and comparative physiological tests were performed with type strains Tenacibaculum aestuarii JCM 13491(T) and Tenacibaculum lutimaris DSM 16505 T, since they exhibit 16S rRNA gene sequence similarities above 97%. These data, as well as phylogenetic analyses, suggest that strain B390(T) (=DSM 18961(T) =JCM 14633(T)) should be classified as the type strain of a novel species within the genus Tenacibaculum, for which the name Tenacibaculum adriaticum sp. nov. is proposed

On the Finite Size Scaling in Disordered Systems

The critical behavior of a quenched random hypercubic sample of linear size $L$ is considered, within the ``random-$T_{c}$'' field-theoretical mode, by using the renormalization group method. A finite-size scaling behavior is established and analyzed near the upper critical dimension $d=4-\epsilon$ and some universal results are obtained. The problem of self-averaging is clarified for different critical regimes.Comment: 21 pages, 2 figures, submitted to the Physcal Review

Two-Dimensional Quantum XY Model with Ring Exchange and External Field

We present the zero-temperature phase diagram of a square lattice quantum spin 1/2 XY model with four-site ring exchange in a uniform external magnetic field. Using quantum Monte Carlo techniques, we identify various quantum phase transitions between the XY-order, striped or valence bond solid, staggered Neel antiferromagnet and fully polarized ground states of the model. We find no evidence for a quantum spin liquid phase.Comment: 4 pages, 4 figure

Ecofog - Gagner en compétitivité et réduire les impacts environnementaux de la filière foie gras

On a worldwide scale, France is the leading producer of foie gras. To maintain this leadership, the sector must remain competitive and control its production costs while meeting specific societal and environmental expectations such as preservation of product quality, respect for animal welfare or limited use of natural resources. The aim of the project was to develop innovative production systems that would limit the impacts of feed and its surrounding practices on the competitiveness of the sector and the environment. An experimental approach was associated with a multi-criteria sustainability assessment (farm level), complemented by an analysis of production cost (farm level) and environmental impacts (product level). Two domains were studied: one related to feed, and the other related to ambient conditions during breeding and force-feeding. Several issues have been identified to progress. Reducing the amount of food distributed (-10%) appears as a possible solution to reduce feeding costs during rearing. The use of sorghum is also of interest but its use should be limited to the rearing phase. Lastly, semi-open air system, compared to open-air system, helps to improve IC (Consumption Index) and reduces animal heterogeneity and mortality. This project also provided original results related to the understanding of mechanisms involved in body temperature regulation of ducks on the one hand and on the other hand to LCA results of different innovations. Lastly, it contributed to the creation of two tools: one to drill ventilation ducts and another to calculate production costs. The results were disseminated to the professionals throughout the project in order to make all data available.À l’échelle mondiale, la France est le premier producteur de foie gras. Afin de conserver ce leadership, la filière doit rester compétitive et maîtriser ses coûts de production tout en répondant à des attentes sociétales et environnementales spécifiques telles que la préservation de la qualité des produits, le respect du bien-être animal ou la gestion économe des ressources. Le projet ECOFOG avait pour objectif de développer des systèmes de production innovants, permettant de limiter l’impact de l’alimentation des canards et des pratiques qui l’entourent pour gagner en compétitivité de la filière et diminuer l’impact environnemental de la filière. La démarche expérimentale a été associée à une démarche d’évaluation multicritère de la durabilité à l’échelle de l’atelier, complétée par une analyse des coûts de production à l’échelle de l’atelier et des impacts environnementaux à l’échelle du produit. Deux axes d’étude ont en particulier été développés : l’un autour de l’aliment, et l’autre autour des conditions d’ambiance en élevage et en gavage.Plusieurs pistes ont été identifiées pour progresser. La réduction de la quantité d’aliment distribué (-10%) est une solution possible pour réduire les coûts d'alimentation. L’utilisation de sorgho présente par ailleurs un intérêt environnemental mais son utilisation devrait être limitée à la phase d’élevage. En termes de bâtiments enfin, le système semi plein-air, comparé au système plein-air, contribue à améliorer l’IC (Indice de Consommation) et réduit les écarts de poids entre les animaux et la mortalité. Ce projet a permis d’obtenir des résultats originaux sur les mécanismes impliqués dans la régulation de la température corporelle des canards. Il a aussi permis d’évaluer les impacts environnementaux de la production de foie gras, et d’analyser les conséquences des différents systèmes de production innovants sur les performances, les coûts et la durabilité de la production. Il a enfin contribué à la création de deux outils utiles pour la filière : un outil d’aide au perçage des gaines de ventilation en atelier de gavage et un outil de calcul du coût de production. Ces résultats ont été largement diffusés vers les professionnels afin de rendre l’ensemble de ces données disponibles

Wang-Landau study of the 3D Ising model with bond disorder

We implement a two-stage approach of the Wang-Landau algorithm to investigate the critical properties of the 3D Ising model with quenched bond randomness. In particular, we consider the case where disorder couples to the nearest-neighbor ferromagnetic interaction, in terms of a bimodal distribution of strong versus weak bonds. Our simulations are carried out for large ensembles of disorder realizations and lattices with linear sizes $L$ in the range $L=8-64$. We apply well-established finite-size scaling techniques and concepts from the scaling theory of disordered systems to describe the nature of the phase transition of the disordered model, departing gradually from the fixed point of the pure system. Our analysis (based on the determination of the critical exponents) shows that the 3D random-bond Ising model belongs to the same universality class with the site- and bond-dilution models, providing a single universality class for the 3D Ising model with these three types of quenched uncorrelated disorder.Comment: 7 pages, 7 figures, to be published in Eur. Phys. J.

A step towards a computing grid for the LHC experiments : ATLAS data challenge 1

The ATLAS Collaboration at CERN is preparing for the data taking and analysis at the LHC that will start in 2007. Therefore, a series of Data Challenges was started in 2002 whose goals are the validation of the Computing Model, of the complete software suite, of the data model, and to ensure the correctness of the technical choices to be made for the final offline computing environment. A major feature of the first Data Challenge (DC1) was the preparation and the deployment of the software required for the production of large event samples as a worldwide distributed activity. It should be noted that it was not an option to "run the complete production at CERN" even if we had wanted to; the resources were not available at CERN to carry out the production on a reasonable time-scale. The great challenge of organising and carrying out this large-scale production at a significant number of sites around the world had therefore to be faced. However, the benefits of this are manifold: apart from realising the required computing resources, this exercise created worldwide momentum for ATLAS computing as a whole. This report describes in detail the main steps carried out in DC1 and what has been learned form them as a step towards a computing Grid for the LHC experiments

Analytical and numerical study of hardcore bosons in two dimensions

We study various properties of bosons in two dimensions interacting only via onsite hardcore repulsion. In particular, we use the lattice spin-wave approximation to calculate the ground state energy, the density, the condensate density and the superfluid density in terms of the chemical potential. We also calculate the excitation spectrum, $\omega({\bf k})$. In addition, we performed high precision numerical simulations using the stochastic series expansion algorithm. We find that the spin-wave results describe extremely well the numerical results over the {\it whole} density range $0\leq \rho \leq 1$. We also compare the lattice spin-wave results with continuum results obtained by summing the ladder diagrams at low density. We find that for $\rho \leq 0.1$ there is good agreement, and that the difference between the two methods vanishes as $\rho^2$ for $\rho \to 0$. This offers the possibility of obtaining precise continuum results by taking the continuum limit of the spin-wave results for all densities. Finaly, we studied numerically the finite temperature phase transition for the entire density range and compared with low density predictions.Comment: 10 pages, 8 figures include