Twining characters, orbit Lie algebras, and fixed point resolution

We describe the resolution of field identification fixed points in coset conformal field theories in terms of representation spaces of the coset chiral algebra. A necessary ingredient from the representation theory of Kac Moody algebras is the recently developed theory of twining characters and orbit Lie algebras, as applied to automorphisms representing identification currents.Comment: Latex, 24 pages. Slightly extended version of lectures by J. Fuchs at a workshop in Razlog (Bulgaria) in August 199

Debugging Scandal: The Next Generation

In 1997, the general lack of debugging tools was termed "the debugging scandal". Today, as new languages are emerging to support software evolution, once more debugging support is lagging. The powerful abstractions offered by new languages are compiled away and transformed into complex synthetic structures. Current debugging tools only allow inspection in terms of this complex synthetic structure; they do not support observation of program executions in terms of the original development abstractions. In this position paper, we outline this problem and present two emerging lines of research that ease the burden for debugger implementers and enable developers to debug in terms of development abstractions. For both approaches we identify language-independent debugger components and those that must be implemented for every new language. One approach restores the abstractions by a tool external to the program. The other maintains the abstractions by using a dedicated execution environment, supporting the relevant abstractions. Both approaches have the potential of improving debugging support for new languages. We discuss the advantages and disadvantages of both approaches, outline a combination thereof and also discuss open challenges

Stellungnahme zu den Steuerreformvorschlägen von CDU/CSU (Konzept 21) und FDP (Berliner Entwurf)

In seinem Jahresgutachten 2003/2004 hat der Sachverständigenrat ausführlich die Mängel der deutschen Einkommens- und Unternehmensbesteuerung aufgezeigt. Steuerpolitischer Handlungsbedarf besteht in erster Linie bei der Unternehmensbesteuerung. (1) Zur Stärkung der Standortattraktivität sind die tariflichen und effektiven Steuerbelastungen der unternehmerischen Gewinne zu senken. (2) Außerdem müssen durch eine Integration der Unternehmensbesteuerung in die Einkommensteuer Verzerrungen bei Finanzierungsentscheidungen und der Rechtsformwahl beseitigt oder zumindest abgebaut werden. (3) Daneben geht es um eine grundlegende Vereinfachung des Steuersystems und die Gewährleistung einer gerechten Besteuerung. Die Forderung nach Steuervereinfachung und Steuergerechtigkeit lässt sich grundsätzlich durch eine neutrale Besteuerung verwirklichen. (4) Schließlich sind bei einer Reform des Steuersystems die EU-rechtlichen Vorgaben zu beachten

Optical emission spectroscopy for rate and composition control of plasma-assisted EBPVD processes

Currently, EB-PVD of YSZ layers is the standard process for TBC on turbine components. Due to the similar vapor pressures of yttria and zirconia, processing is relatively uncomplicated, and the good performance of this material in various aspects is not easy to beat. However, the increasing need for enhanced turbine efficiency and reduced emissions requires new approaches and developments. This calls for improved TBC systems or ceramic-based turbine components coated with EBC systems, which go hand in hand with the use of new admixed materials and more complex coating compositions. Consequently, the corresponding PVD processes become more challenging as well and should be aided by enhanced monitoring and control means therefore. Plasma activation of various PVD processes has been shown to be key to success in order to combine high-rate film growth with the requested film properties. The vapor and the reactive gas species are excited, ionized, and dissociated. The energy of charged particles impinging the substrate surface can be tuned resulting in layers with desired density, composition, hardness, or microstructure. The effect of plasma activation by using a hollow cathode arc discharge onto the morphology of YSZ layers [1,2] and its potential for coating of dense EBC’s [3] have been discussed previously. In this paper, another aspect of utilizing a plasma discharge in the vapor cloud will be discussed. Due to excitation of neutrals and ions, element-specific light emission occurs which can be analyzed by optical emission spectroscopy (OES). The spectrum can be used to monitor and control the PVD process. As an example, YSZ has been evaporated by EB-PVD, and an emission line of excited zirconium neutrals has been used to maintain a constant deposition rate. Moreover, metallic zirconium and yttrium have been co-evaporated in oxygen atmosphere by spotless arc-assisted EB-PVD [4], and the vapor species have been monitored by OES. In another project, co-evaporation of several metallic ingots has been performed by the jumping beam method, and an OES-based control loop is being developed to automatically control the EB power input and feeding speed of the individual ingots. This plasma-based OES control method has a considerable potential for the development of reliable, well-defined deposition processes. In addition, the co-evaporation approach may be of increased interest to deposit new complex TBC and EBC systems. [1] G. Mattausch et al.: 55th SVC Annual Technical Conference Proceedings, 179-185 (2012) [2] B. Zimmermann et al.: Poster presentation at ECI Thermal Barrier Coatings IV, Irsee, Germany (2014) [3] B. Zimmermann et al.: Poster presentation at ECI Advanced Ceramic Matrix Composites, Santa Fe, USA (2017) [4] B. Scheffel et al.: Surface & Coatings Technology 316, 155–161 (2017

Kluges Konstellationen. Alexander Kluges Fortsetzung der Kritischen Theorie mit narrativen Mitteln

Alexander Kluge befreit die Kritische Theorie aus ihrer diskursiven Verschanzung der letzten Jahrzehnte und verknüpft sie auf ästhetische wie bildungspolitische Weise wieder mit Gesellschaft. Dabei arbeitet er im Grunde nach vier Prinzipien: Entschleunigung, Subjektivierung, konstellative Darstellung und kooperative Gegenproduktion. Durch alle Freiheiten eines Erzählers gelingt es ihm darüber hinaus, auch die theoretischen Grundlagen insbesondere Benjamins und Adornos weiterzuentwickeln. Die Idee der Konstellation, die laut Kluge von Balzac stammt und die Adorno und Eisenstein in sein Leben bringen, hat in Walter Benjamins „Idee als Konfiguration“ eine weitere prominente Begleitung: „Die Ideen sind ewige Konstellationen und indem die Elemente als Punkte in derartigen Konstellationen erfaßt werden, sind die Phänomene aufgeteilt und gerettet zugleich.“ Das ausformulierte Ziel lautet deshalb: „Rettung der Phänomene“ und „Darstellung der Ideen“.Alexander Kluge affranchit la Théorie critique de son cloisonnement discursif de ces dernières décennies et rétablit – tant esthétiquement qu’au niveau de la politique éducative – sa liaison avec la société. Son travail fait fond sur quatre principes : ralentissement intentionnel, subjectivation, représentation par constellation, contre-production coopérative. Grâce à toutes les libertés dont dispose un conteur/narrateur, Kluge parvient en outre à développer les fondements théoriques de Benjamin et Adorno. L’idée de la constellation qui, selon Kluge, provient de Balzac, mais que lui ont apportée Adorno et Eisenstein, trouve dans « L’idée comme configuration » de Walter Benjamin un autre accompagnement célèbre : « Les idées sont des constellations éternelles, et dans la mesure où les éléments sont saisis comme des points à l’intérieur de ces constellations, les phénomènes sont en même temps dispersés et sauvés. » Dans ce cadre, le but proclamé est dès lors : « sauvetage des phénomènes » et « représentations des idées. »Alexander Kluge has liberated Critical theory from its discursively entrenched position of the last few decades and is attempting to reconnect it to society in the fields of both aesthetics and educational policy. Through this process, his work falls under the following four principles: deceleration, subjectivization, constellative (re)presentation/dramaturgy and finally cooperative counter-production. Furthermore, utilising the kind of artistic liberties which are granted to a narrator, he succeeds in developing theoretical principles, especially those of Benjamin and Adorno. The idea of constellation, which, according to Kluge, came from Balzac and was animated into life by Adorno and Eisenstein, is also connected to Walter Benjamin’s “idea of configuration”: “The ideas are eternal constellations and in grasping the elements in such constellations, the phenomena are divided up and redeemed at the same time.” In this context, the declared ambitions are: “(re)presentation of ideas” and “salvation of phenomena”

From Dynkin diagram symmetries to fixed point structures

Any automorphism of the Dynkin diagram of a symmetrizable Kac-Moody algebra induces an automorphism of the algebra and a mapping between its highest weight modules. For a large class of such Dynkin diagram automorphisms, we can describe various aspects of these maps in terms of another Kac-Moody algebra, the `orbit Lie algebra'. In particular, the generating function for the trace of the map on modules, the `twining character', is equal to a character of the orbit Lie algebra. Orbit Lie algebras and twining characters constitute a crucial step towards solving the fixed point resolution problem in conformal field theory.Comment: Latex, 60 pages (extended version 63 pages), 4 uuencoded figures Formula (6.25) corrected. While this correction might be important in applications of our work, the results of the paper are not affected by it. In the present submission the "extended version" is default. In this version the corrected formula is (6.32

Motion compensation with a scanned ion beam: a technical feasibility study

This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

The potential of plasma activation for EB-PVD of EBC systems on CMC components

Gas turbines are subject of intense research and development in order to meet increasing demands on fuel efficiency, reduction of emissions, or enhanced power. One of the major keys is improving the thermal efficiency by increased gas temperature within the turbine. In the hot turbine section, nickel-based superalloy components with thermal barrier coatings are utilized, which are still being refined and improved. Nevertheless, in order to significantly increase temperature capability and turbine efficiency, silicon-based non-oxide ceramics are being investigated and introduced as new base materials, allowing for lower-weight components operating at elevated temperatures. Severe weight losses due to water vapor corrosion, increasing temperature demands and other challenges require protecting environmental barrier coatings (EBC) to be applied on such ceramic components. The development of EBC systems already went through a number of generations, including mullite and barium-strontium-aluminosilicate (BSAS) based layers, various rear earth silicate coatings, hafnia or zirconia doping, and more. Utilizing processing techniques based on plasma spray and EB-PVD methods, tremendous progress has been made regarding the performance of the coating systems. However, improving the thermal, mechanical and chemical stability as well as the resistance against attack from calcia-magnesia-alumina-silica (CMAS) deposits, water vapor corrosion, or damage due to particle impact is still a hot topic of further development. Fraunhofer FEP has been developing PVD processes as well as corresponding hardware such as EB guns and plasma sources in a large field of applications for decades. Selected examples are corrosion protection layers on steel, oxygen and water vapor permeation barrier coatings on plastic webs, hard and wear-resistant coatings on tools, or TBC. In the most cases, plasma activation of the PVD process is the key to success in order to combine high-rate film growth with the requested film properties. The vapor and – if prevalent – the reactive gas species are excited, ionized, and dissociated. The energy of charged particles impinging the substrate surface can be tuned resulting in layers with desired density, composition, hardness, or microstructure. From FEP’s experience, it can be derived that the beneficial effect of plasma activation could complement the above mentioned EBC developments to address the present challenges. Please click Additional Files below to see the full abstract