Un des grand défis de la physique actuelle est la quantification de la gravit é. La théorie d’Einstein est remarquable pour ses prédictions. Malheureusement, elle reste une théorie classique et de ce fait en désaccord avec les progrès actuels en physique des particules qui montrent qu’à faible distance, une théorie physique doit être quantique. Une des pistes pour résoudre ce problème est d’étudier la version classique de la gravité dans l’espoir d’en déduire des propriétés ou même la forme de la théorie quantique.<p><p>Un des outils pour étudier une theorie est la notion de dualité. On dit que deux théories sont duales quand elles décrivent le même système par des moyens différents. La dualité est le dictionnaire permettant de passer d’une description à l’autre. Dans ma thèse, j’ai étudié deux dualités s’appliquant à la gravité en 4 dimensions.<p><p>La première est connue sous le nom de dualité électromagnétique. A l’origine, cette dualité s’applique à l’électromagnétisme où elle échange les rôles du champ & / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

In dieser Dissertation erweitern wir die Ideen des Yangian-Bootstrap-Algorithmus auf Feynman-Diagramme mit massiven Teilchen. Ausgehend von der massiven dual-konformen Symmetrie der N = 4 Super-Yang-Mills Theorie auf dem Coulomb-Zweig konstruieren wir einen Satz von bilokalen Yangian Level-Eins Generatoren und zeigen, dass sie eine unendliche Anzahl von planaren ein- und zwei-Schleifen-Diagrammen vernichten. Wir beschreiben außerdem wie der dual-konforme Level-Eins Impuls-Operator auf eine massive Verallgemeinerung des gewöhnlichen spezial-konformen Generators im Impulsraum abgebildet wird. Als nächstes wenden wir den Yangian-Bootstrap-Algorithmus mit großem Erfolg auf eine Reihe von massiven Ein-Schleifen-Diagrammen mit verallgemeinerten Propagatorexponenten und in beliebiger Anzahl von Raumdimensionen an. Im Spezialfall der dual-konformen Integrale, deren Propagatorexponenten sich zur Raumdimension addieren, finden wir neue sehr einfache Darstellungen durch hypergeometrische Funktionen, die eine natürliche Verallgemeinerung für Diagramme mit beliebig vielen äußeren Punkten erlauben. Außerdem diskutieren wir Aspekte des Yangian-Bootstrap-Algorithmus in Minkowski-Raumzeit am Beispiel des masselosen Box-Integrals. Wir zeigen, dass dessen Yangian-Symmetrie gemeinsam mit seinen diskreten Permutationssymmetrien das Box-Integrals bis auf 12 unbestimmte Konstanten komplett festlegt. Schließlich schlagen wir vor, dass das Auftreten von Yangian-Symmetrie in massiven Fischnetz-Diagrammen mit deren Rolle als Ein-Spur-Streuamplituden in einer massiven Fischnetz-Theorie zusammenhängen könnte. In Analogie mit der masselosen Fischnetz-Theorie zeigen wir, wie diese Theorie als Deformation der N = 4 Super-Yang-Mills Theorie auf dem Coulomb-Zweig definiert werden kann. Wir diskutieren eine bestimmte Klasse von planaren Grenzfällen, in der die off-shell Streuamplituden der Theorie eine massive dual-konforme Symmetrie sowie Yangian-Symmetrie aufweisen. / In this dissertation, we extend the ideas of the Yangian bootstrap algorithm to massive Feynman diagrams. Based on the massive dual-conformal symmetry of Coulomb branch N = 4 super-Yang-Mills theory, we construct a set of bi-local Yangian level-one generators and show that they annihilate infinite classes of massive planar Feynman integrals at one and two loops. We also describe how the dual-conformal level-one momentum generator maps to a massive deformation of the ordinary momentum space special conformal generator. We then apply the Yangian bootstrap to a set of massive one-loop integrals with generalised propagator powers and in an arbitrary number of space dimensions to great success. In the special case of dual-conformal integrals, whose propagator powers sum to the space dimension, we find very simple novel hypergeometric structures, suggesting a natural generalisation to diagrams with an arbitrary number of external points. In the particular case of the massless box integral we also discuss elements of the Yangian bootstrap in Minkowski space. We show that its Yangian and discrete permutation symmetries constrain it up to 12 undetermined constants. We then derive the values of these constants via analytic continuation from the box integral in the Euclidean region. Finally, we provide evidence that the appearance of Yangian symmetry for massive fishnet diagrams is related to their role as colour-ordered scattering amplitudes in a massive fishnet theory. We show how to construct this theory from Coulomb branch N = 4 super-Yang-Mills theory, paralleling the original construction of the massless fishnet theory. We discuss how a particular class of planar limits leads to the emergence of massive dual-conformal symmetry as well as massive Yangian symmetry for the theory’s off-shell scattering amplitudes.

Share-based payments have become a popular form of employee remuneration, largely for its potential to address the agency problem and are especially effective when made to senior employees. Accounting standards require companies to report share-based payments made to employees as expenses in their financial statements, but extant South African tax legislation does not permit a deduction where shares are awarded to serve as incentives for senior employees. This is due to the fact that the courts do not view the issue of a company‟s own shares as “expenditure”. South African tax legislation presently contains a special tax deduction for shares awarded to employees, but this provision‟s low monetary limit and restrictive requirements are considered to be inadequate, where the intention is to provide adequate incentives to senior employees in order to address the agency problem. The objective of this study is to evaluate whether sufficient grounds exist, based on the principles of sound tax policy, for the legislature to enact a special tax deduction for share-based payments, which would serve as an adequate incentive to senior employees. The evaluation found that the current tax position infringes upon several principles of sound tax policy and that an intervention by the legislature is required. / MCom (South African and International Tax), North-West University, Potchefstroom Campus, 2015

Share-based payments have become a popular form of employee remuneration, largely for its potential to address the agency problem and are especially effective when made to senior employees. Accounting standards require companies to report share-based payments made to employees as expenses in their financial statements, but extant South African tax legislation does not permit a deduction where shares are awarded to serve as incentives for senior employees. This is due to the fact that the courts do not view the issue of a company‟s own shares as “expenditure”. South African tax legislation presently contains a special tax deduction for shares awarded to employees, but this provision‟s low monetary limit and restrictive requirements are considered to be inadequate, where the intention is to provide adequate incentives to senior employees in order to address the agency problem. The objective of this study is to evaluate whether sufficient grounds exist, based on the principles of sound tax policy, for the legislature to enact a special tax deduction for share-based payments, which would serve as an adequate incentive to senior employees. The evaluation found that the current tax position infringes upon several principles of sound tax policy and that an intervention by the legislature is required. / MCom (South African and International Tax), North-West University, Potchefstroom Campus, 2015

Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Please refer to full text for abstract. / AFRIKAANSE OPSOMMING: Sien asb volteks vir opsomming.

This thesis is an empirically based, theoretical discussion of the process of decision making in relation to Library Management Systems (LMS). Although the conceptualization of the LMS decision process in rational terms, common in many LMS selection models, may be useful in different respects, here the process is viewed from a social constructivist stance. It is argued that due to the complexities involved, the potential choice of an LMS does not necessarily reflect the superiority of the chosen LMS based on objective inherent qualities. Nevertheless, libraries continually choose new systems and in many of these selection processes, the chosen system is perceived as the optimal choice. In this study, therefore focus is placed on examining the way in which this shared perception is constructed. Three theoretical views are adopted as the research framework, including Brunsson’s views on the process of decision making and its consequences, Collins’s views on methodological symmetry and construction of conceptual order, and finally Giddens’s views on duality of structure and the social order. Observations, interviews, and document studies are the methods employed in four different case studies that each lasted from 10 months to two years. In this study an array of different factors were found to be influential during the long process of the LMS decision making. It was also found that although the norms of rationality were striven for, and shared perceptions of rationality were constructed, the complexities involved did not allow a true rational choice by determination of all the options, projection of future needs, evaluation of the identified options, and selection of the optimal outcome. Instead, the different activities and happenings during the process helped construct a shared perception of the possible courses of action and optimality of the decision outcomes. Based on this study and with the help of the theoretical framework, it was suggested that an LMS choice is only one potential consequence of the LMS decision process; other consequences include legitimization, action, responsibility, and constructions of conceptual and social order. Through this study, the importance of the day-to-day actions and interactions (at micro level) and their wider implications for the construction of shared perceptions and shaping and reshaping of social structures are highlighted. This thesis contributes towards an alternative conceptualization of the process of LMS decision making. It may also have implications for the library practice, LMS related research, and educational programs within LIS. / <p>Akademisk av handling som med tillstånd av samhällsvetenskapliga fakulteten vid Göteborgs universitet för vinnande av doktorsexamen framläggs till offentlig</p><p>granskning kl. 13:15 fredagen den 1 oktober 2010, i hörsalen M404, Högskolan i Borås.</p><p>Avhandlingen har tilldelats den prestigefyllda utmärkelsen ”The 2011 Emerald/EFMD Outstanding Doctoral Research Awards”. The thesis has been awarded with the prestigious honor of ”The 2011 Emerald/EFMD Outstanding Doctoral Research Awards”</p>

Anthradithiophene (ADT) derivatives have proven to be a front-runner in the world of small molecule semiconductors for organic electronics and optoelectronics. This is mainly due to the improved stability, easy tuning of chemical and physical properties, and impressive device performance that these molecules possess, especially in organic field effect transistors (OFET) and organic photovoltaics (OPV). The second chapter of this dissertation shows that reducing the amount of alkylsilylethynyl groups, used for functionalizing and solubilizing the ADT backbone, does alter the chemical, physical and crystallographic properties of ADTs. These changes offer the opportunity to study and observe different intermolecular interactions as well as monitoring their influence on sulfur scrambling in solid state. Additionally, from the early days ADTs and functionalized ADTs have been synthesized as isomeric mixtures. In chapter three, I demonstrate a new and simple method that can separate the syn and anti isomers of the F-TES-ADT and F-TEG-ADT chromatographically. The effects of isomeric purity on crystal packing and field effect transistor performance were studied extensively. Chapter four of this dissertation reveals a new generation of acceptor (electron poor) ADT derivatives obtained by attaching cyanide as electron withdrawing group (EWG) to the ADT chromophore. An extensive study was conducted on CN-ADT (acceptor) molecules in small molecule (F-TES-ADT) donor/ small molecule (CN-ADT) acceptor binary BHJ blends as well as P3HT/CN-ADT/PCBM ternary BHJ blends. Photophysical studies of the Donor/ acceptor blends (interface, domains, and crystal orientation) were conducted to obtain a better understanding of the film morphology and its effect on solar cell performance. Finally, the last part of the dissertation, Chapter five, focus on studying singlet fission in ADT derivatives, as well as the effect of varying the size of the alkylsilylethynyl functional group (used for solubilizing the ADT backbone) on altering the electronic couplings and how can that potentially affect the singlet fission rate in these molecules. We also tried to inspect the extent of the correlation between long-range order in crystal packing and singlet fission by monitoring singlet fission rate and efficiency for ADT derivatives with different thin film morphologies.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Crossing symmetry relates scattering and annihilation processes to each other. Its derivation is straightforward in perturbative approaches to quantum field theory: it merely reflects the exchange of in- and outgoing states in Feynman diagram computations. In soliton models, the situation is much more complicated because the scattering and the annihilation processes concern distinct topological sectors that are not related by any continuous transformation. In this thesis a simple soliton model will be employed to address this problem numerically. First, in the unit topological sector we extract asymptotically the phase shift of the scattering process of a wave packet off the kink-solution. To this end we solve the time-dependent equation of motion of the non-integrable '4 field model in (1+1) spacetime dimensions for two distinct initial conditions: the wave packet in a trivial vacuum background and in the background of the kink-solution. Second, in the topologically trivial sector we present numerical solutions of the kink– antikink interaction in the same model. We find that the final state of this interaction varies dramatically with the impact velocity. As result, we analyze our numerical solutions for the kink–antikink collisions system in two regimes. For the initial velocity of the system less than some critical velocity, vc 0:26, the kink and the antikink either annihilate or inelastically scatter. On the other hand, the kink and the antikink always inelastically scatter when the initial velocity of the system is higher than this critical velocity. However, the scattering processes of the kink–antikink with initial velocity below and above the critical velocity are different. Below the critical velocity the kink and the antikink collide and always undergo n-bounces (n 2) before they depart to infinity. When the initial velocity of the system is higher than vc, the kink and the antikink depart to infinity after only one bounce. We present a qualitative description for these bounce effects between the kink and the antikink motivated by earlier studies as well as our numerical simulations. We utilize collective coordinates to study the dynamics of the kink–antikink system in two degrees of freedom. In this regime, we modify the ansätze of the kink–antikink system from earlier studies to account for relativistic effects. We perform a comparison between this approximation and the full system. We end our discussion of this sector by discussing the scattering data for the inelastic scattering and the annihilation processes of the kink–antikink. Third, we compare the extracted scattering data for the scattering process of a wave packet off the kink-solution and the annihilation process of the kink–antikink to each other. Finally, these studies of different sectors allow us to make a conjecture about the validity of crossing symmetry within the non-integrable '4 field model. / AFRIKAANSE OPSOMMING: Kruising-simmetrie beskryf ’n verband tussen verstrooiings- en vernietigingsprosesse. Die afleiding daarvan binne die raamwerk van steuringsteorie is eenvoudig: dit behels bloot die omruil van ingaande en uitgaande toestande in die Feynman-diagram. In soliton-modelle is die situasie egter meer ingewikkeld aangesien die verstrooiings- en vernietigingsprosesse in verskillende topologiese sektore plaasvind wat nie deur kontinue transformasies aan mekaar gekoppel is nie. In hierdie tesis word daar van ’n eenvoudige soliton-model gebruik gemaak om hierdie probleem numeries te ondersoek. Eerstens word die faseverskuiwing van die verstrooiingsproses van ’n golfpakkie vanaf ’n kinkoplossing asimptoties in die topologiese eenheidssektor bepaal. Vir hierdie doel word die tydafhanklike bewegingsvergelykings van die klassieke, nie-integreerbare 4-veldeteorie in (1+1) dimensionele ruimte-tyd opgelos. Twee beginkondisies word ondersoek: ’n golfpakkie in die triviale vakuum agtergrond asook in die kinkoplossing agtergrond. Tweedens ondersoek ons ook numeriese oplossings vir die kink-antikink wisselwerking binne die triviale topologiese sektor van dieselfde model. Hier vind ons dat die finale toestand van hierdie wisselwerkingsproses op ’n uiters sensitiewe wyse van die impaksnelheid afhang. Ons ondersoek gevolglik die numeriese oplossings vir die kink-antikink botsings in twee gebiede. Vir beginsnelhede onder die kritieke snelheid vc 0:26 sal die kink en antikink mekaar óf vernietig óf nie-elasties verstrooi. In teenstelling hiermee sal die kink-antikink altyd nie-elastiese verstrooiing ondergaan as die beginsnelheid die kritieke snelheid oorskry. Die aard van die verstrooiingsprosesse vir beginsnelhede bo en onder die kritieke snelheid is egter verskillend. Onder die kritieke snelheid sal die kink en antikink ’n n-bots proses (n 2) ondergaan voor hulle finaal van mekaar weg beweeg. Bo die kritieke snelheid sal die kink-antikink egter net ’n enkele botsing ondergaan en dan uitmekaar beweeg. Ons lewer ’n kwalitatiewe beskrywing vir die bons-effek tussen die kink en antikink wat deur vorige studies asook ons numeriese resultate gemotiveer word. Ons maak gebruik van ’n kollektiewe koördinaatstelsel om die dinamika van die kink-antikink in terme van twee vryheidsgrade te bestudeer. In hierdie gebied pas ons ook die ansatz vir die kink-antikink stelsel aan om relatiwistiese effekte in ag te neem. Ons vergelyk dan hierdie benadering met die oplossing van die volle sisteem. Die bespreking van hierdie sektor word afgesluit met ’n analise van die verstrooiingsdata vir die verstrooiing- en vernietingsprosesse van die kink-antikink. Derdens vergelyk ons die verstrooiingsdata vir die verstrooiing van ’n golfpakkie vanaf ’n kinkoplossing met die van die vernietigingsproses van die kink-antikink. Ons studie van die verskillende sektore laat ons dan toe om ’n vermoede te formuleer oor die geldigheid van kruissing-simmetrie binne die nie-integreerbare 4-model.

Dans ce travail, nous proposons des procédures de test paramétriques et nonparamétrique localement et asymptotiquement optimales au sens de Hajek et Le Cam, pour trois modèles d'asymétrie. La construction de modèles d'asymétrie est un sujet de recherche qui a connu un grand développement ces dernières années, et l'obtention des tests optimaux (pour trois modèles différents) est une étape essentielle en vue de leur mise en application. Notre approche est fondée sur la théorie de Le Cam d'une part, pour obtenir les propriétés de normalité asymptotique, bases de la construction des tests paramétriques optimaux, et la théorie de Hajek d'autre part, qui, via un principe d'invariance permet d'obtenir les procédures non-paramétriques. Nous considérons dans ce travail deux classes de distributions univariées asymétriques, l'une fondée sur un développement d'Edgeworth (décrit dans le Chapitre 1), et l'autre construite en utilisant un paramètre d'échelle différent pour les valeurs positives et négatives (le modèle de Fechner, décrit dans le Chapitre 2). Le modèle d'asymétrie elliptique étudié dans le dernier chapitre est une généralisation multivariée du modèle du Chapitre 2. Pour chacun de ces modèles, nous proposons de tester l'hypothèse de symétrie par rapport à un centre fixé, puis par rapport à un centre non spécifié. Après avoir décrit le modèle pour lequel nous construisons les procédures optimales, nous obtenons la propriété de normalité locale asymptotique. A partir de ce résultat, nous sommes capable de construire les tests paramétriques localement et asymptotiquement optimaux. Ces tests ne sont toutefois valides que si la densité sous-jacente f est correctement spécifiée. Ils ont donc le mérite de déterminer les bornes d'efficacité paramétrique, mais sont difficilement applicables. Nous adaptons donc ces tests afin de pouvoir tester les hypothèses de symétrie par rapport à un centre fixé ou non, lorsque la densité sous-jacente est considérée comme un paramètre de nuisance. Les tests que nous obtenons restent localement et asymptotiquement optimaux sous f, mais restent valides sous une large classe de densités. A partir des propriétés d'invariance du sous-modèle identifié par l'hypothèse nulle, nous obtenons les tests de rangs signés localement et asymptotiquement optimaux sous f, et valide sous une vaste classe de densité. Nous présentons en particulier, les tests fondés sur les scores normaux (ou tests de van der Waerden), qui sont optimaux sous des hypothèses Gaussiennes, tout en étant valides si cette hypothèse n'est pas vérifiée. Afin de comparer les performances des tests paramétriques et non paramétriques présentés, nous calculons les efficacités asymptotiques relatives des tests non paramétriques par rapport aux tests pseudo-Gaussiens, sous une vaste classe de densités non-Gaussiennes, et nous proposons quelques simulations.

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