Solving String Field Equations: New Uses for Old Tools

It is argued that the (NS-sector) superstring field equations are integrable, i.e. their solutions are obtainable from linear equations. We adapt the 25-year-old solution-generating "dressing" method and reduce the construction of nonperturbative superstring configurations to a specific cohomology problem. The application to vacuum superstring field theory is outlined.Comment: Talk presented by O.L. at the 35th International Symposium Ahrenshoop on the Theory of Elementary Particles, Berlin, Germany, 26-30 Aug 2002; v2: minor corrections, textheight adjuste

Design and Analysis of Composite Panels

European aircraft industry demands for reduced development and operating costs, by 20% and 50% in the short and long term, respectively. Contributions to this aim are provided by the completed project POSICOSS (5thFP) and the running follow-up project COCOMAT (6thFP), both supported by the European Commission. As an important contribution to cost reduction a decrease in structural weight can be reached by exploiting considerable reserves in primary fibre composite fuselage structures through an accurate and reliable simulation of postbuckling up to collapse. The POSICOSS team developed fast procedures for postbuckling analysis of stiffened fibre composite panels, created comprehensive experimental data bases and derived design guidelines. COCOMAT builds up on the POSICOSS results and considers in addition the simulation of collapse by taking degradation into account. The results comprise an extended experimental data base, degradation models, improved certification and design tools as well as design guidelines. The projects POSICOSS and COCOMAT develop improved tools which are validated by experimental results obtained during the projects. Because the new tools must consider a wide range of different aspects a lot of different structures had to be tested. These structures were designed under different design objectives. For the design process the consortium applied already available simulation tools and brought in their own design experience. This paper deals with the design process within both projects and the analysis procedure applied within this task. It focuses on the experience of DLR on the design and analysis of stringer stiffened CFRP panels gained in the frame of these projects

The Impact of Surplus Distribution on the Risk Exposure of With Profit Life Insurance Policies Including Interest Rate Guarantees

This paper analyzes the numerical impact of different surplus distribution mechanisms on the risk exposure of a life insurance company selling with profit life insurance policies with a cliquet-style interest rate guarantee. Three representative companies are considered, each using a different type of surplus distribution: A mechanism, where the guaranteed interest rate also applies to surplus that has been credited in the past, a slightly less restrictive type in which a guaranteed rate of interest of 0% applies to past surplus, and a third mechanism that allows for the company to use former surplus in order to compensate for underperformance in “bad” years. Our study demonstrates that regulators should be very careful in deciding which design of a distribution mechanism is to be enforced. Within our model framework, a distribution mechanism of the third type yields preferable results with respect to the considered risk measure. In particular, throughout the analysis, our representative company 3 faces ceteris paribus a significantly lower shortfall risk than the other two companies. Requiring “strong” guarantees puts companies at a significant competitive disad¬vantage relative to insurers which are subject to regulation that only requires the third type of surplus distribution mechanism. This is particularly true, if annual minimum participation in the insurer’s investment returns is mandatory for long term contracts

The Impact of Surplus Distribution on the Risk Exposure of With Profit Life Insurance Policies Including Interest Rate Guarantees

This paper analyzes the numerical impact of different surplus distribution mechanisms on the risk exposure of a life insurance company selling with profit life insurance policies with a cliquet-style interest rate guarantee. Three representative companies are considered, each using a different type of surplus distribution: A mechanism, where the guaranteed interest rate also applies to surplus that has been credited in the past, a slightly less restrictive type in which a guaranteed rate of interest of 0% applies to past surplus, and a third mechanism that allows for the company to use former surplus in order to compensate for underperformance in “bad” years. Our study demonstrates that regulators should be very careful in deciding which design of a distribution mechanism is to be enforced. Within our model framework, a distribution mechanism of the third type yields preferable results with respect to the considered risk measure. In particular, throughout the analysis, our representative company 3 faces ceteris paribus a significantly lower shortfall risk than the other two companies. Requiring “strong” guarantees puts companies at a significant competitive disad¬vantage relative to insurers which are subject to regulation that only requires the third type of surplus distribution mechanism. This is particularly true, if annual minimum participation in the insurer’s investment returns is mandatory for long term contracts.life insurance; interest guarantees; surplus distribution

Probabilistic Approach for better Buckling Knock-down Factors of CFRP Cylindrical Shells - Tests and Analyses

The industry in the fields of civil and mechanical engineering, and in particular of aerospace demands for significantly reduced development and operating costs. Reduction of structural weight at safe design is one avenue to achieve this objective. The running ESA (European Space Agency) study Probabilistic Aspects of Buckling Knock Down Factors – Tests and Analyses contributes to this goal by striving for an improved buckling knock-down factor (the ratio of buckling loads of imperfect and perfect structures) for unstiffened CFRP (carbon fiber reinforce plastics) cylindrical shells, and by validation of the linear and non-linear buckling simulations based on test results. DLR is acting as study contractor. The paper presents an overview about the DLR buckling tests, the measurement setup and the buckling simulations which are done so far, and gives an outlook to the results which are expected until the end of the running project

SU(2) WZW D-branes and quantized worldvolume U(1) flux on S^2

We discuss possible D-brane configurations on SU(2) group manifolds in the sigma model approach. When we turn the boundary conditions of the spacetime fields into the boundary gluing conditions of chiral currents, we find that for all D-branes except the spherical D2-branes, the gluing matrices R^a_{b} depend on the fields, so the chiral Kac-Moody symmetry is broken, but conformal symmetry is maintained. Matching the spherical D2-branes derived from the sigma model with those from the boundary state approach we obtain a U(1) field strength that is consistent with flux quantization.Comment: 10 pages, Latex, several corrections (the previous version was not approved by the first two authors

Sharing is Caring:Multiprocessor Scheduling with a Sharable Resource

We consider a scheduling problem onm identical processors sharing an arbitrarily divisible resource. In addition to assigning jobs to processors, the scheduler must distribute the resource among the processors (e.g., for three processors in shares of 20%, 15%, and 65%) and adjust this distribution over time. Each job j comes with a size pj ∈R and a resource requirement rj >0. Jobs do not benefit when receiving a share larger than rj of the resource. But providing them with a fraction of the resource requirement causes a linear decrease in the processing efficiency. We seek a (non-preemptive) job and resource assignment minimizing the makespan. Our main result is an efficient approximation algorithm which achieves an approximation ratio of 2+1/(m−2). It can be improved to an (asymptotic) ratio of 1+1/(m−1) if all jobs have unit size. Our algorithms also imply new results for a well-known bin packing problem with splittable items and a restricted number of allowed item parts per bin. Based upon the above solution, we also derive an approximation algorithm with similar guarantees for a setting in which we introduce so-called tasks each containing several jobs and where we are interested in the average completion time of tasks (a task is completed when all its jobs are completed)

Das Verhältnis von res und verba: zu den Narrativen der Dinge

Dinge in Texten haben maßgeblich an der Konstruktion imaginärer Welten teil. Sie können intradiegetisch angefasst werden, sie riechen, haben ein spezifisches Gewicht und doch sind sie für die Leser in erster Linie: durch Zeichen repräsentierte Dinge. So einfach und so komplex lässt sich die doppelbödige Ausgangslage beschreiben, auf der die folgenden Überlegungen gründen. Denn auf diese Beobachtung kann Literaturwissenschaft in unterschiedlicher Weise reagieren: An einem Ende der Skala beschäftigt sie sich hauptsächlich mit der Zeichenhaftigkeit von repräsentierten Dingen, den Verweischarakteristiken, Funktionen und Bedeutungen, am anderen mit der Materialität, der Stofflichkeit und Widerständigkeit. Beide Pole haben ihre Verfechter, jeder der Ansätze seine Tradition und Konjunkturen. Bevor dieser Hintergrund, die Begrifflichkeit und der Forschungsstand erläutert werden, stehen in der Folge zwei literarische Beispiele im Zentrum, an denen gezeigt wird, welche Fragen sich mit literarischen Dingen stellen. Ludwig Tiecks 'Des Lebens Überfluß' (1838) und Ilija Trojanows 'Auf der Flucht' (2017) entstammen ganz unterschiedlichen Epochen und Kontexten, deshalb lässt sich an ihnen auch eine Bandbreite von Fragestellungen aufzeigen