Precision direct photon and W-boson spectra at high p_T and comparison to LHC data

The differential p_T spectrum for vector boson production is computed at next-to-leading fixed order and including the resummation of threshold logarithms at next-to-next-to-leading logarithmic accuracy. A comparison is made to ATLAS data on direct photon and W production at high transverse momentum p_T, finding excellent agreement. The resummation is achieved by factorizing contributions associated with different scales using Soft-Collinear Effective Theory. Each part is then calculated perturbatively and the individual contributions are combined using renormalization group methods. A key advantage of the effective theory framework is that it indicates a set of natural scale choices, in contrast to the fixed-order calculation. Resummation of logarithms of ratios of these scales leads to better agreement with data and reduced theoretical uncertainties.Comment: 24 pages, 10 figures; v2: journal version; v3: corrections in (20), (37), (38

A Massively Parallel Algorithm for the Approximate Calculation of Inverse p-th Roots of Large Sparse Matrices

We present the submatrix method, a highly parallelizable method for the approximate calculation of inverse p-th roots of large sparse symmetric matrices which are required in different scientific applications. We follow the idea of Approximate Computing, allowing imprecision in the final result in order to be able to utilize the sparsity of the input matrix and to allow massively parallel execution. For an n x n matrix, the proposed algorithm allows to distribute the calculations over n nodes with only little communication overhead. The approximate result matrix exhibits the same sparsity pattern as the input matrix, allowing for efficient reuse of allocated data structures. We evaluate the algorithm with respect to the error that it introduces into calculated results, as well as its performance and scalability. We demonstrate that the error is relatively limited for well-conditioned matrices and that results are still valuable for error-resilient applications like preconditioning even for ill-conditioned matrices. We discuss the execution time and scaling of the algorithm on a theoretical level and present a distributed implementation of the algorithm using MPI and OpenMP. We demonstrate the scalability of this implementation by running it on a high-performance compute cluster comprised of 1024 CPU cores, showing a speedup of 665x compared to single-threaded execution

New Risks Ahead:The Eastward Enlargement of the Eurozone

Eastward enlargement is one of the hot topics in European economics. The accession of central and eastern European Countries (CEEC) into the European Union (EU) is accompanied by an extension of the eurozone to this region. This paper surveys likely outcomes and challenges of this specific feature of EU enlargement. Moreover, the ar-ticle represents the start of an international research project dealing with these ques-tions. Research is structured along different markets. Hence, the impact of an adoption of the euro is analysed for capital and labour markets as well as with respect to exchange rate and monetary policies. Our main position is that the euro has in general beneficiary ef-fects for the CEEC and the current EU in all examined markets. However, these bene-fits evolve mainly in the long run, whereas the short-term costs of adaptation to the new situation may be high. Although we believe that the present value of long-term benefits exceeds these costs, it is by no means clear that policy-makers will share this view. Due to the usual political-economy transformation, the assessment of costs and benefits may be different for politicians than compared to any overall perspective. If of-ficial policies become unforeseeable, so will private behaviour. International investors may reverse their capital flows, draining precious liquidity, and leading to currency and financial crises whenever they perceive the authorities’ commitment to EMU less credi-ble. This article highlights some thinkable mechanisms how any such crisis could evolve. It, thus, sets the agenda for further research, mainly, with the focus on appropriate policy strategies to keep adaptation costs as low as possible, minimise other external risks, without hampering the long-term benefits.EMU, EU enlargement, monetary integration

Indium-Gallium Segregation in CuInx_{x}Ga1−x_{1-x}Se2_2: An ab initio based Monte Carlo Study

Thin-film solar cells with CuIn$_x$Ga$_{1-x}$Se$_2$ (CIGS) absorber are still far below their efficiency limit, although lab cells reach already 19.9%. One important aspect is the homogeneity of the alloy. Large-scale simulations combining Monte Carlo and density functional calculations show that two phases coexist in thermal equilibrium below room temperature. Only at higher temperatures, CIGS becomes more and more a homogeneous alloy. A larger degree of inhomogeneity for Ga-rich CIGS persists over a wide temperature range, which may contribute to the low observed efficiency of Ga-rich CIGS solar cells

An Approach for Simplified Subsystem Replacement and Reconfiguration in Multimodal VR, AR and Other Simulation Frameworks

Nowadays, modern software for the development of augmented and virtual reality applications is designed with the aim to simplify its usability in order to provide services to a wider user base. In this context, our paper presents a novel approach to make the replacement and reconfiguration of a simulation framework's subsystems possible, without being bound by the restrictions, current plug-in strategies incur, or the need of manipulating its source code. Code manipulation requires a deep understanding of software engineering and the framework's software design, including all dependencies among the subsystems. For this purpose, common simulation systems were examined and their restrictions identified. Solutions of different problems in this context were elaborated and are discussed in this paper

Resummation for W and Z production at large pT

Soft-Collinear Effective theory is used to perform threshold resummation for W and Z production at large transverse momentum to next-to-next-to-leading logarithmic accuracy including matching to next-to-leading fixed-order results. The results agree very well with data from the Tevatron, and predictions are made for the high-pT spectra at the LHC. While the higher-log terms are of moderate size, their inclusion leads to a substantial reduction of the perturbative uncertainty. With these improvements, the PDF uncertainties now dominate the error on the predicted cross section.Comment: 5 pages, 5 figure

A smooth cascade of wrinkles at the edge of a floating elastic film

The mechanism by which a patterned state accommodates the breaking of translational symmetry by a phase boundary or a sample wall has been addressed in the context of Landau branching in type-I superconductors, refinement of magnetic domains, and compressed elastic sheets. We explore this issue by studying an ultrathin polymer sheet floating on the surface of a fluid, decorated with a pattern of parallel wrinkles. At the edge of the sheet, this corrugated profile meets the fluid meniscus. Rather than branching of wrinkles into generations of ever-smaller sharp folds, we discover a smooth cascade in which the coarse pattern in the bulk is matched to fine structure at the edge by the continuous introduction of discrete, higher wavenumber Fourier modes. The observed multiscale morphology is controlled by a dimensionless parameter that quantifies the relative strength of the edge forces and the rigidity of the bulk pattern.Comment: 4 pages, 4 figure