Higher order QCD results for the fermionic contributions of the Higgs-boson decay into two photons and the decoupling function for the MSbar renormalized fine-structure constant

We compute the decoupling function of the MSbar renormalized fine-structure constant up to four-loop order in perturbative QCD. The results are used in order to determine the related top-quark contributions to the Higgs-boson decay into two photons in the heavy top-quark mass limit to order alpha_s^4.Comment: 19 pages, 4 figure

SusOrganic - Development of quality standards and optimised processing methods for organic produce - Final report

The SusOrganic project aimed to develop improved drying and cooling/freezing processes for organic products in terms of sustainability and objective product quality criteria. Initially, the consortium focused on a predefined set products to investigate (fish, meat, fruits and vegetables). Contacting participants in the fruit and vegetable sector showed that there is only little perceived need for making changes for the improvement of the processes. At the same time, it became clear that hops and herb producers (drying) face several challenges in terms of product quality and cost of drying processes. Therefore, the range of products was extended to these products. The results of a consumer survey conducted as part the project showed clearly that consumers trust in the organic label, but also tend to mix up the term organic with regional or fair ­trade. Further, the primary production on farm and not the processing is explicitly included in the consumers’ evaluation of sustainability. Appearance of organic products was found to be one of the least important quality criteria or attributes regarding buying decisions. However, there are indications that an imperfect appearance could be a quality attribute for consumers, as the product then is perceived to be processed without artificial additives. Regarding drying operations, small scale producers in the organic sector often work with old and/or modified techniques and technologies, which often leads to an inefficient drying processes due to high energy consumptions and decreased product quality. Inappropriate air volume flow and distribution often cause inefficient removal of the moisture from the product and heterogeneous drying throughout the bulk. Guidelines for improvement of the physical setup of existing driers as well as designs for new drying operations, including novel drying strategies were developed. Besides chilling and freezing, the innovative idea of superchilling was included into the project.The superchilled cold chain is only a few degrees colder than the refrigeration chain but has a significant impact on the preservation characteristic due to shock frosting of the outer layer of the product and the further distribution of very small ice crystals throughout the product during storage. Super­chilling of organically grown salmon eliminated the demand of ice for transport, resulting in both, a reduction of energy costs and a better value chain performance in terms of carbon foot printing. This is mainly due to the significantly reduced transport volume and weight without the presence of ice. The product quality is not different but the shelf life is extended compared to chilled fish. This means that the high quality of organic salmon can be maintained over a longer time period, which can be helpful,e.g. to reach far distant markets. The same trend was found for superchilled organic meat products such as pork and chicken. The consortium also developed innovative noninvasive measurement and control systems and improved drying strategies and systems for fruits, vegetables, herbs, hops and meat. Those systems are based on changes occurring inside the product and therefore require observation strategies of the product during the drying process. Through auditing campaigns as well as pilot scale drying tests it has been possible to develop optimisation strategies for both herb and hops commodities, which can help reduce microbial spoilage and retain higher levels of volatile product components whilst reducing the energy demands. These results can be applied with modifications to the other commodities under investigation. The environmental and cost performance of superchilling of salmon and drying of meat, fruit and vegetables were also investigated and the findings indicated that both superchilling and drying could improve sustainability of organic food value chains especially in case of far distant markets. An additional outcome of the project, beyond the original scope was the development of a noninvasive, visual sensor based detection system for authenticity checks of meat products in terms of fresh and prefrozen meats

Leptonic contributions to the effective electromagnetic coupling at four-loop order in QED

The running of the effective electromagnetic coupling is for many electroweak observables the dominant correction. It plays an important role for deriving constraints on the Standard Model in the context of electroweak precision measurements. We compute the four-loop QED corrections to the running of the effective electromagnetic coupling and perform a numerical evaluation of the different gauge invariant subsets.Comment: 26 pages, 4 figure

Sparse Vector Distributions and Recovery from Compressed Sensing

It is well known that the performance of sparse vector recovery algorithms from compressive measurements can depend on the distribution underlying the non-zero elements of a sparse vector. However, the extent of these effects has yet to be explored, and formally presented. In this paper, I empirically investigate this dependence for seven distributions and fifteen recovery algorithms. The two morals of this work are: 1) any judgement of the recovery performance of one algorithm over that of another must be prefaced by the conditions for which this is observed to be true, including sparse vector distributions, and the criterion for exact recovery; and 2) a recovery algorithm must be selected carefully based on what distribution one expects to underlie the sensed sparse signal.Comment: Originally submitted to IEEE Signal Processing Letters in March 2011, but rejected June 2011. Revised, expanded, and submitted July 2011 to EURASIP Journal special issue on sparse signal processin