We present two re-derivations of the Scharnhorst effect. The latter was first obtained in 1990 by Klaus Scharnhorst, soon followed by Gabriel Barton, and consists in the theoretical prediction that the phase velocity of photons propagating in a Casimir vacuum normal to the plates would be larger than c. The first derivation given in the present work is relevant for the debates that have taken place in the physics literature regarding a possible greater-than-c value of the signal velocity. Indeed because the phase velocity result also held for the group velocity, the issue soon arose as to whether the same could be said for the signal velocity. Several arguments were presented against this notion, notably to the effect that measurement uncertainties would preclude such a measurement. These notably relied on the fact that the known phase velocity result is only valid within a certain frequency regime. Scharnhorst and Barton responded by arguing that given their previous result, the Kramers-Kronig relations imply one of two options: either the greater-than-c result holds for the signal velocity as well, or the Casimir vacuum behaves like an amplifying medium for some frequencies. Furthermore, the effect was later rederived and generalized within the framework of an effective metric approach, which has been argued to obviate the worries regarding causal paradoxes often associated with the possibility of faster-than-c signalling. However concerns related to theory errors as well as to the measurement uncertainties that had surfaced in the earlier debate have remained salient. By re-deriving the phase velocity using Soft-Collinear Effective Theory (SCET), one can address some of these concerns. Indeed, with regard to theory errors, SCET provides us with a framework where higher order corrections are known to be power-suppressed because SCET ensures that the expansion parameters are multiplied by factors of order 1. As a result, with due qualifications inherent to the nature of effective field theory, the result obtained within the SCET approach cannot be invalidated by higher order corrections. Furthermore, the theoretical description offered by SCET provides an argument relevant to the point that measurement uncertainties would prevent measuring the signal speed to be faster-than-c. Indeed, SCET implies the interaction between the Casimir vacuum and the propagating photon to be such that the latter would have the same phase velocity irrespective of its frequency. This in turn would entail that its signal velocity would be equal to this phase velocity, which is faster-than-c. The second calculation presented is concerned with the physical interpretation of the Scharnhorst effect, and constitutes an attempt at re-deriving it within source theory. Existing derivations imply that the Scharnhorst effect can be attributed to vacuum fluctuations. Other physical effects that share this feature have also been derived without any reference to the vacuum, but as due to source fields instead. We attempt a similar derivation for the Scharnhorst effect.

An investigation of Hawking radiation and a method for calculating particle creation in Schwarzschild spacetime using a quantum Langevin approach is presented in this thesis. In particular we shall show that an oscillator confined to a free-fall trajectory in Schwarzschild spacetime radiates as a result of such motions, and this radiation can be interpreted as Hawking radiation. In chapter 1 we present a literature review of the underlying concept: the Unruh effect. We also present some introductory material pertinent to the calculations. Chapter 2 is concerned with the case of a thin collapsing shell to form a black hole in Schwarzschild anti-de Sitter spacetime. We determine the temperature of the black hole to be T[subscript H] = h(r[subscript h])/4π = κ/2π where h(r[subscript h]) is the factorization of the conformal factor, r is the radial coordinate with the location of the horizon situated atr = r[subscript h], and κ the surface gravity. We also calculate the stress tensor at early and late spacetimes which allows us to calculate the renormalized stress-tensor {T[subscript μν]} which satisfies the semi-classical Einstien field equations. In chapter 3 we examine the case of a harmonic oscillator in 2D Schwarzschild spacetime and we show that the choice of trajectory is responsible for making the oscillator radiate. In chapter 4 we derive a quantum Langevin equation for the oscillator in the Heisenberg picture. By solving this equation using the Wigner-Weiskopff approximation we show that, in the case of an oscillator confined to a free fall trajectory in Schwarzschild spacetime, the oscillator radiates with respect to the Boulware vacuum. In agreement with Hawking[1] we obtain a temperature of the black hole as T = 1/8πM[subscript B]. In chapter 5 we present our conclusions and recommendations for further work.

Automotive active suspension, advanced seismic testing, and force/torque emulations of space manipulators are examples of applications, where the hydraulic actuator force control is required. In double-rod hydraulic actuators, the actuator force is the differential pressure across the actuator multiplied by the piston effective area. The focus of this work is to control the actuator force of a double-rod hydraulic actuator by controlling the differential pressure across the actuator. The double-rod hydraulic actuator of this study is run by two independent circuits: 1) electro-hydraulic actuation and 2) electro-hydrostatic actuation. In general, developing controllers for hydraulic actuators is challenging due to the presence of parametric uncertainties and uncertain nonlinearities. Also, a specific challenge in force control of hydraulic actuators is the limiting effect of environment dynamics on the maximum achievable tracking bandwidth. Considering the above challenges, in this research for the first time, quantitative feedback theory (QFT) is employed to control the hydraulic actuator force. Using QFT, a robust, linear, fixed-gain, and low-order controller is designed for each actuation system which: (i) keeps the closed-loop response within desired tracking bounds (ii) guarantees the closed-loop stability around desired operating points, (iii) rejects disturbance, and (iv) achieves desired tracking bandwidth. Among the performance criteria, special attention is paid to achieve high tracking bandwidth. Trade-offs between different performance criteria towards achieving high tracking bandwidth, are discussed. Experimental results are presented to validate that the performance criteria are satisfied by the designed QFT controllers. The QFT controllers are synthesized based on the families of frequency responses of the hydraulic actuation systems, which limits the stability results of the closed-loop system, only for these families of the frequency responses. In this thesis, to investigate the nonlinear stability of the closed-loop systems with QFT controllers, for the first time, Takagi-Sugeno (T-S) fuzzy modeling and its corresponding stability theory are used. The stability conditions are presented in the form of linear matrix inequalities (LMIs). As a result, the nonlinear stability of the designed QFT controllers for both the actuation systems is proven in the presence of parametric uncertainties. / February 2016

Submitted by ROBERTO PAULO CORREIA DE ARAÚJO (ppgorgsistem@ufba.br) on 2017-05-19T23:58:33Z No. of bitstreams: 1 TESE - Marilda - 2016 F.pdf: 1951206 bytes, checksum: f0d79f0e2b09130f482d4c5c8d7f00d3 (MD5) / Made available in DSpace on 2017-05-19T23:58:34Z (GMT). No. of bitstreams: 1 TESE - Marilda - 2016 F.pdf: 1951206 bytes, checksum: f0d79f0e2b09130f482d4c5c8d7f00d3 (MD5) / Introdução: A avaliação de risco para tuberculose (TB) em profissionais da saúde baseia-se no número de indivíduos doentes atendidos nas instituições, na evidência de sua transmissão entre pessoas dentro das instituições, ou cálculo de taxas de conversão do teste cutâneo tuberculínico (TCT). Sugere-se que os resultados negativos para este teste sejam repetidos periodicamente, de acordo com o risco que a instituição apresente e, ou, após exposições ocupacionais. O fato de apenas 10% das pessoas infectadas com Mγcobacterium tuberculosis desenvolverem a doença clínica sugere que diversos mecanismos podem desempenhar um papel importante na imunopatogênese da doença. Estudos genéticos estão sendo desenvolvidos com o objetivo de identificar possíveis marcadores de predisposição ou proteção ao desenvolvimento desta doença e sugerem que o desequilíbrio na produção de citocinas pró e anti-inflamatórias tem um importante papel na TB. Objetivo: Avaliar a liberação de interferon gama (IFN-γ) e o polimorfismo de citocinas nos PS com TCT de repetição, negativo e positivo, que trabalham em uma unidade de referência secundária e terciária em TB. Métodos: A população do estudo foi constituída por 48 profissionais TCT de repetição negativo, com resultado < 5 mm e 45 TCT positivo > 10 mm. O DNA genômico foi extraído a partir de sangue total, utilizando o kit de extração de DNA mini spin Kasvi. Foi realizada a genotipagem das citocinas (IL6, IL10, TNF, IFN-γ, TGFB1) e a associação entre o polimorfismo +874T/A do geneIFN- γ ,o resultado do ensaio de liberação de interferon gama IGRA (QFT®) e o TCT. Resultados: Não foi observada diferença estatística no polimorfismo do gene IFN-γ +874 T/A e o resultado do IGRA e TCT. A concordância entre o TCT e IGRA foi feita utilizando o índice Kappa que mostrou κ=0,24. Os resultados relativos aos fenótipos previstos de alto (TT), intermediário (TA) e baixo produtor (AA) de IFN-γ, a partir do polimorfismo na posição +874T/A, em ambos os grupos mostrou que a maior frequência foi o de baixo produtor. Ao analisar o grupo TCT+ / IGRA +, os dados mostram correlação dos testes in vivo e in vitro para reatividade em 24 indivíduos. O polimorfismo desses indivíduos tem o perfil dos fenótipos previstos de baixo produtor, sendo apenas 6 de intermediário e 3 de alto produtor. Conclusão: A concordância entre o TCT e o IGRA na população estudada é mediana e não foi observada diferença no polimorfismo do gene IFN-γ+874T/A para frequência de fenótipo previsto de baixo produtor, comparando os grupos do estudo e seus respectivos IGRA. Os polimorfismos dos genes IFN γ +874T/A, TNF -308G/A, IL6 -174G/C IL10 - 1082G/A, -819C/T e -592C/A e TGFβ1 -509 C/T não parecem ser marcadores de predisposição ou proteção ao desenvolvimento da TBIL. Foi encontrada diferença estatística no gene TGF1 +869 T/C.

The main focus of the work is the construction of a quantum spacetime emerging from theory.

In this text we explore the case of pure Yang-Mills amplitudes in 5 spacetime dimensions for vector particles. Extending current toolsets such as the Spinor-Helicity formalism in 5D would be beneficial to the study of the various cases of super Yang-Mills and supergravity. In this text we provide an expression for the 5D BCFW shifts and test them in the 4-point setting. A method for obtaining the 5-point gluon amplitude is presented as well as a way to classify possible building blocks of the ansatz. We also provide a non-trivial expression for the 5-point case. The text begins with a short review of Spinor-Helicity formalism in 4D is given at the beginning followed by a discussion of its extension to 5D. Next, we review the pure Yang-Mills theory and modern methods of amplitude calculations. Finally we discuss our methods and results. / Vi utforskar fallet med rena Yang-Mills-amplituder i 5 rymdtidsdimensioner för vektorpartiklar. Utvidgningen av Spinor-Helicity-formalismen i 5D skulle vara fördelaktig för studiet av de olika fallen av super Yang-Mills och supergravitation. I denna avhandling ger vi ett uttryck för 5D BCFW-skiften och tillämpar dem i 4-punktsinställningen. Vi presenterar en metod för att erhålla 5-punkts gluonamplituden och ett sätt att klassificera möjliga byggstenar i ansatsen. Med hjälp av dessa utvecklar vi ett icke-trivialt uttryck för 5-punktsfallet i 5D SH-variabler. Texten börjar med en kortöversikt över Spinor-Helicity-formalismen i 4D som ges i början följt av en diskussion om dess utvidgning till 5D. Därefter granskar vi den rena Yang-Mills-teorin och moderna metoder för amplitudberäkningar och slutligen diskuterar vi våra metoder och resultat

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Die perturbative Quantenfeldtheorie ist das am weitesten entwickelte Modell, zur präzisen Analyse vieler verschiedener physikalischer Phänomene. Das Standardwerkzeug der perturbativen QFT sind Feynman-Diagramme. Bei Rechnungen bis zu einer Schleife ist aber auch der Wärmekern eine mächtige Technik. Um in der QFT, über die Störungstheorie hinauszugehen ist Symmetrie von großer Bedeutung. Insbesondere die konforme Symmetrie schränkt die Korrelatoren stark ein. In dieser Arbeit wird sie mit der Average Null Energy Condition (ANEC) kombiniert, um die Hofman-Maldacena-Schranken für die Anomaliekoeffizienten in vier Dimensionen abzuleiten. Im Folgenden untersuchen wir verschiedene Probleme der perturbativen Quantenfeldtheorie. Zunächst studieren wir die Weyl-Anomalie für einen nicht-konformen freien Skalar in einer vierdimensionalen gekrümmten Raumzeit. Wir verstehen die Definition der Anomalie diagrammatisch ohne klassische Symmetrie und wir interpretieren die bekannte Wärmekernberechnung präzise. Dann untersuchen wir Eichtheorien mit höheren Ableitungen in sechs Dimensionen. Diese sind natürliche Kandidaten, um perturbativ nicht-unitäre konforme Theorien zu konstruieren. Die Berechnung erfolgt mit der Wärmekernmethode und wir leiten den allgemeinen Ausdruck des, zuvor nicht Bekannten, relevanten Koeffizienten her. Supersymmetrie sowie das Hinzufügen des Yang-Mills-Terms werden ebenfalls berücksichtigt. Schließlich beginnen wir die Untersuchung der Implikationen der ANEC auf nicht-konforme Feldtheorien, angefangen mit dem selbst-wechselwirkenden Skalar in vier Dimensionen. Der Energiefluss eines Zustands mit einer einzelnen Feldeinfügung wird berechnet. Ausgehend von den perturbativen Euklidischen Korrelatoren im Impulsraum konstruieren wir die relevante Wightman-Funktion, um den Energiefluss auszuwerten. Die Berechnung ist kompliziert, aber wir erhalten das erwartete Ergebnis und eröffnen so die Möglichkeit, interessantere Zustände zu untersuchen. / Perturbative quantum field theory is our most developed framework to accurately analyse many physical phenomena. The standard tool is Feynman diagrams, but at one-loop the heat kernel is also a powerful technique. It is however difficult to go beyond perturbation theory, and symmetry is a key factor. In particular, conformal symmetry strongly restricts the correlators, and have been combined with the average null energy condition (ANEC) to derive the Hofman-Maldacena bounds on the anomaly coefficients in four dimensions. In this thesis we study different problems in perturbative quantum field theory. First, we study the Weyl anomaly for a non-conformal free scalar in a four-dimensional curved spacetime. We diagrammatically understand the definition of the anomaly without classical symmetry, and we precisely interpret the well-known heat kernel calculation. Then, we study higher-derivative gauge theories in six dimensions. These theories are the natural candidate to perturbatively construct non-unitary conformal theories. The calculation is done with the heat kernel method and we derive the general expression of the relevant coefficient, which was previously unknown. Supersymmetry or the addition of a Yang-Mills term are also considered. Finally, we initiate the study of the consequence of the ANEC on non-conformal field theories with the example of the self-interacting scalar in four dimensions. The energy flux of a state with a single field insertion is computed. Starting from the perturbative momentum-space Euclidean correlators, we construct the relevant Wightman function to evaluate the energy flux. The calculation is considerably complicated, but we recover the expected result, opening the possibility of studying more interesting states.