Finite-Size Effects in Lattice QCD with Dynamical Wilson Fermions

As computing resources are limited, choosing the parameters for a full Lattice QCD simulation always amounts to a compromise between the competing objectives of a lattice spacing as small, quarks as light, and a volume as large as possible. Aiming to push unquenched simulations with the Wilson action towards the computationally expensive regime of small quark masses we address the question whether one can possibly save computing time by extrapolating results from small lattices to the infinite volume, prior to the usual chiral and continuum extrapolations. In the present work the systematic volume dependence of simulated pion and nucleon masses is investigated and compared with a long-standing analytic formula by Luescher and with results from Chiral Perturbation Theory. We analyze data from Hybrid Monte Carlo simulations with the standard (unimproved) two-flavor Wilson action at two different lattice spacings of a=0.08fm and 0.13fm. The quark masses considered correspond to approximately 85 and 50% (at the smaller a) and 36% (at the larger a) of the strange quark mass. At each quark mass we study at least three different lattices with L/a=10 to 24 sites in the spatial directions (L=0.85-2.08fm).Comment: 21 pages, 20 figures, REVTeX 4; v2: caption of Fig.7 corrected, one reference adde

Variational approach to interfaces in random media: negative variances and replica symmetry breaking

A Gaussian variational approximation is often used to study interfaces in random media. By considering the 1+1 dimensional directed polymer in a random medium, it is shown here that the variational Ansatz typically leads to a negative variance of the free energy. The situation improves by taking into account more and more steps of replica symmetry breaking. For infinite order breaking the variance is zero (i.e. subextensive). This situation is reminiscent of the negative entropies in mean field spin glass models, which were also eliminated by considering infinite order replica symmetry breaking.Comment: 8 pages revtex. Submitted to Journal de Physique (France

New Two-Dimensional Models of Supernova Explosions by the Neutrino-Heating Mechanism: Evidence for Different Instability Regimes in Collapsing Stellar Cores

The neutrino-driven explosion mechanism for core-collapse supernovae in its modern flavor relies on the additional support of hydrodynamical instabilities in achieving shock revival. Two possible candidates, convection and the so-called standing accretion shock instability (SASI), have been proposed for this role. In this paper, we discuss new successful simulations of supernova explosions that shed light on the relative importance of these two instabilities. While convection has so far been observed to grow first in self-consistent hydrodynamical models with multi-group neutrino transport, we here present the first such simulation in which the SASI grows faster while the development of convection is initially inhibited. We illustrate the features of this SASI-dominated regime using an explosion model of a 27 solar mass progenitor, which is contrasted with a convectively-dominated model of an 8.1 solar mass progenitor with subsolar metallicity, whose early post-bounce behavior is more in line with previous 11.2 and 15 solar mass explosion models. We analyze the conditions discriminating between the two different regimes, showing that a high mass-accretion rate and a short advection time-scale are conducive for strong SASI activity. We also briefly discuss some important factors for capturing the SASI-driven regime, such as general relativity, the progenitor structure, a nuclear equation of state leading to a compact proto-neutron star, and the neutrino treatment. Finally, we evaluate possible implications of our findings for 2D and 3D supernova simulations. Our results show that a better understanding of the SASI and convection in the non-linear regime is required.Comment: 12 pages, 13 figures; revised version accepted for publication in Ap

THE NON-ENGLISH LECTURERS’ READING COMPETENCE IN READING ENGLISH TEXT AT HIGHER EDUCATION IN CENTRAL JAVA

Abstract Nowadays, the government offers a lot of scholarships to non-English lecturers to study abroad. However, only a few that could get the scholarship due to their inability to communicate in English or to comprehend English texts. In this paper, therefore, the writers want to find out whether or not the non-English lecturers could get some benefits to comprehend the English texts after being given the manual book developed by the researchers. Besides, the researchers also want to find out the elements of the text that are easy or difficult to be understood by them. The method used in this research was experimental research with the population of non English lecturers at Kopertis Wilayah VI. One hundred (100) people from several universities in Central Java were taken as the sample. Two kinds of instrument for collecting the data, namely reading test and interview were used. Reading test material was taken from the modification of the TOEFL test with the intention to know the ability of non English lecturers in reading English texts and which elements of the text are difficult or easy to be mastered by the lecturers. The interview was used to know the lecturers’ perception on the appropriateness of the manual book given and whether they got some benefits from it

Predicting the potential geographical distribution of the harlequin ladybird, Harmonia axyridis, using the CLIMEX model - BioControl

Harmonia axyridis (Pallas, 1773) (Coleoptera: Coccinellidae) is a ladybird beetle native to temperate and subtropical parts of Asia. Since 1916 populations of this species have been introduced throughout the world, either deliberately, or by accident through international transport. Harmonia axyridis was originally released as a classical biological control agent of aphid and coccid pests in orchards and forests, but since 1994 it is also available as a commercial product for augmentative control in field and greenhouse crops. It is a very voracious and effective natural enemy of aphids, psyllids and coccids in various agricultural and horticultural habitats and forests. During the past 20 years, however, it has successfully invaded non-target habitats in North America (since 1988), Europe (1999) and South America (2001) respectively in a short period of time, attacking a wide range of non-pest species in different insect orders. Becoming part of the agricultural commercial pathway, it is prone to being introduced into large areas across the world by accident. We use the CLIMEX programme (v2) to predict the potential geographical distribution of H. axyridis by means of matching the climate of its region of origin with other regions in the world and taking in account biological characteristics of the species. Establishment and spread seem likely in many regions across the world, including those areas which H. axyridis has already invaded (temperate Europe, North America). Based on the CLIMEX prediction a large part of Mediterranean Europe, South America, Africa, Australia and New Zealand seem highly suitable for long-term survival of H. axyridis as well. In addition we evaluate CLIMEX as a strategic tool for estimating establishment potential as part of an environmental risk assessment procedure for biological control agents we discuss biological and ecological aspects necessary to fine-tune its establishment and spread in areas after it has been introduce

Benefits from clinicians and healthcare organisations engaging in research

In Editor’s Choice, Godlee supports and re-emphasises the positive points about National Institute for Health Research (NIHR) clinical research networks that are made in Gulland’s article.1 2 We welcome this support for research networks and for the part they can play in a more fully integrated research and healthcare system. Research engagement by clinicians and healthcare organisations is widely held to improve health services performance. However, we found the issue to be complex in our review conducted for the NIHR Health Services and Delivery Research (HS&DR) Programme in 2012-13.3 Thirty three papers were included in the analysis, and 28 were positive about improved performance, although only seven identified improved outcomes rather than improved processes. Diverse mechanisms contributed to these improvements. In a subsequent article we consider more recent evidence,4 including that UK NHS trusts active in research have lower risk adjusted mortality for acute admissions.5 Increased attention to this issue covers not only clinician participation but also organisational developments in the NIHR and NHS, such as Collaborations for Leadership in Applied Health Research and Care (CLAHRC) and Academic Health Science Networks (AHSNs).6 7 These seek to promote better integration of research and healthcare systems by strengthening research networks, developing research capacity, and ensuring that healthcare organisations (both providers and commissioners) see research as an integral component of their overall structure. Such initiatives need to be linked to further empirical analysis that considers not only the research engagement of all relevant actors but also the organisational determinants of the impact on practice of such engagement

Collective Atomic Motion in an Optical Lattice formed inside a High Finesse Cavity

We report on collective non-linear dynamics in an optical lattice formed inside a high finesse ring cavity in a so far unexplored regime, where the light shift per photon times the number of trapped atoms exceeds the cavity resonance linewidth. We observe bistability and self-induced squeezing oscillations resulting from the retro-action of the atoms upon the optical potential wells. We can well understand most of our observations within a simplified model assuming adiabaticity of the atomic motion. Non-adiabatic aspects of the atomic motion are reproduced by solving the complete system of coupled non-linear equations of motion for hundred atoms.Comment: 4 pages, 5 figure

The Renormalization Group Evolution of the CKM Matrix

We compute the renormalization of the complete CKM matrix in the MSbar scheme and perform a renormalization group analysis of the CKM parameters. The calculation is simplified by studying only the Higgs sector, which for the \beta-function of the CKM matrix is at one loop the same as in the full Standard Model. The renormalization group flow including QCD corrections can be computed analytically using the hierarchy of the CKM parameters and the large mass differences between the quarks. While the evolution of the Cabibbo angle is tiny V_{ub} and V_{cb} increase sizably. We compare our results with the ones in the full Standard Model.Comment: Latex, 31 pages, extensions amsmath, epsfig required The complete paper, including figures, is also available via anonymous ftp at ftp://ttpux2.physik.uni-karlsruhe.de/, or via www at http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints