O Modelo Padrão (MP) da física de partículas fornece uma descrição extremamente bem sucedida de todos os dados experimentais atuais. No entanto, temos razões para esperar que ele não seja válido até escalas de energia arbitrariamente altas. No MP a massa do bóson de Higgs é quadraticamente sensível a correções radiativas, sofrendo de grandes problemas de ajuste fino. Isso gera o chamado problema da hierarquia de gauge, cuja solução natural requer nova física na escala TeV. O MP também não fornece nenhuma explicação para a grande hierarquia de massas e ângulos de mistura dos férmions. Os problemas de hierarquia podem ser resolvidos naturalmente em teorias com uma dimensão extra curva. No entanto, a sua versão mais simples viola sabor a nível árvore, em conflito com os dados. Nesta tese investigaremos modelos quadridimensionais que descrevem a física na escala TeV obtidos da discretização de teorias em cinco dimensões no espaço AdS5, segundo o procedimento de desconstrução dimensional. As hierarquias de gauge e das massas dos férmions são geradas naturalmente como no modelo extra-dimensional, satisfazendo ainda os vínculos de sabor e de precisão eletrofraca. Estudaremos também um modelo desconstruído em que o Higgs é um pseudo bóson de Nambu-Goldstone, a fim de obter um Higgs naturalmente leve e dinamicamente localizado / The Standard Model (SM) of particle physics provides an extremely successful description of all current experimental data. However, we have reasons to expect that it cannot be valid up to arbitrarily high energy scales. In the SM the Higgs boson mass is quadratically sensitive to radiative corrections and, hence, suffers from a severe fine-tunning problem. This creates the so-called gauge hierarchy problem, the natural solution of which requires new physics at the TeV scale. The SM also doesnt provide any explanation for the large hierarchy of fermion masses and mixing angles. The hierarchy problems can be naturally solved in theories with a warped extra dimension. However, their simplest version violates flavor at tree level, conflicting with experimental data. In this thesis we investigate four dimensional models that describe physics at the TeV scale obtained from a coarse discretization of five dimensional theories in AdS5 space, by the dimensional deconstruction procedure. The gauge as well as the fermion mass hierarchies are naturally generated in the same manner as in the extra-dimensional model, while also satisfying bonds from flavor physics and precision electroweak data. We also study a deconstructed model in which the Higgs is a pseudo Nambu-Goldstone boson, with the motivation of obtaining a naturally light and localized Higgs.

No âmbito da teoria quântica de campos (TQC) foram estudados modelos de quench exatamente solúveis. Nestes modelos, obteve-se uma generalização do ansatz de Kadanoff-Baym que se mantém em todos intervalos de tempo. Algumas hipóteses sobre fenômenos de não-equilíbrio em TQC em temperaturas finitas foram analisadas e estendidas neste contexto. Para tanto, examinamos as funções de Green nesses modelos e os comparamos com os resultados aproximados que são frequentemente usados na literatura. Um dos modelos descreve sistemas de não-equilíbrio do tipo vítreo. Esses sistemas exibem um comportamento que é compatível com o esperado do teorema de flutuação-dissipação. As propriedades básicas foram consistentemente deduzidas e resultados explícitos para a temperatura efetiva e frequências características foram obtidas. / We have studied exactly quenched models in the context of Quantum Field Theory(QFT). In these models, a generalization of the Kadanoff-Baym ansatz was obtained which holds at all times. Some assumptions concerning non-equilibrium phenomena in QFT at finite temperatures were analysed and extended in this framework. To this end, we have examined the Green\'s functions in these models and compared them with the approximated results which are often used in the literature. One of the models describes non-equilibrium systems of the glassy-kind. Such systems exhibit a behaviour which is compatible with that expected from the fluctuation-dissipation theorem. The basic properties were consistently deduced and explicit results for the effective temperature and characteristic frequencies were obtained.

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The imaginary part of the retarded self energy is of particular interest as it contains a lot of physical information about particle interactions. In higher order loop diagrams the calculation become extremely tedious and if we have to do the same at finite temperature, it includes an extra dimension to the difficulty. In such a condition we require to switch between bases and select the best basis for a particular diagram. We have shown in our calculation that in higher order loop diagrams, at #12;finite temperature, the R/A basis is most convenient on summing over the internal vertices and very efficient on calculating some particular diagrams while the result is most easily interpretable in the Keldysh basis for most other complex diagrams.

The fuzzball model of a black hole is an attempt to resolve the many paradoxes and puzzles of black hole physics that have revealed themselves over the last century. These badly behaved solutions of general relativity have given physicists one of the few laboratories to test candidate quantum theories of gravity. Though little is known about exactly what lies beyond the event horizon, and what the ultimate fate of matter that falls in to a black hole is, we know a few intriguing and elegant semi-classical results that have kept physicists occupied. Among these are the known black hole entropy and the Hawking radiation process.

Η παρούσα διπλωματική εργασία πραγματοποιήθηκε στο τμήμα Σωματιδιακής Φυσικής του Πανεπιστημίου Santiago de Compostela της Ισπανίας και αποτελεί τη μελέτη της υπερσυμμετρίας στις τρεις χωροχρονικές διαστάσεις. Έμφαση δίνεται σε θεωρίες που περιέχουν τον όρο Chern-Simons που παιζεί συμαντικό ρόλο στους τομείς έρευνας της θεωρητικής φυσικής. Αρχικά, εισάγουμε τις εισαγωγικές ένοιες της υπερσυμμετρίας στις τρεις διαστάσεις και ακολούθως μελέτουμε την Ν=1 ελάχιστη θεωρία με διάφορες φυσικές ποσότες που περιέχουν τον όρο Chern-Simons. Στην συνέχεια, μελετάμε τις ABJM θεωρίες και αποδεικνύουμε ότι είναι αναλλοίωτες κάτω από μετασχηματισμούς βαθμίδας. Τέλος υπολογίζουμε τις κβαντικές διορθώσεις στην διαταρακτική θεωρία Chern-Simons. / The present thesis took part in Department of Particle Physics of University of Santiago de Compostela, Spain, and is the study of supersymmetry in three spacetime dimensions. Emphasis is given to theories containing the Chern-Simons term that plays an important role in the research areas of theoretical physics. First, we introduce the notion of supersymmetry in three dimensions and then we study the N = 1 minimal theory with various physical quantitative containing the term Chern-Simons. Then, we study the ABJM theories and prove that they are invariant under gauge transformations. Finally we calculate the quantum corrections to the perturbative Chern-Simons theory.

La notion d’entropie d’intrication a eu un profond impact sur la physique théorique, particulièrement depuis ces dix dernières années. D’abord introduite afin expliquer l’entropie des trous noirs, son champ d’application s’est par la suite ouvert à une grande variété de domaines de recherche, de la matière condensée à la gravitation quantique, de l’information quantique à la théorie quantique des champs. Dans ce contexte scientifique effervescent, l’entropie d’intrication apparait comme un outil central et doit donc intensivement être étudiée. A l’origine de cette thèse se trouve le désir de mieux comprendre cette entropie. D’intéressants développements concernant les effets de bord sur l’entropie d’intrication ont vu le jour récemment. Nous proposons donc d’explorer comment le bord d’un espace affecte l’entropie, en particulier dans la situation où la surface d’intrication intersecte ce bord. Nous présentons des calculs explicites de l’entropie d’intrication en espace plat avec bords. Nous montrons que des termes induits par ces bords apparaissent dans l’entropie et nous soulignons le rôle prépondérant que jouent les conditions aux bords. Nous étudions ensuite la contribution de bord dans le terme logarithmique de l’entropie d’intrication en dimensions trois et quatre. Nous calculons en premier lieu ce terme en théorie des champs pour la théorie N = 4 de Yang-Mills, puis nous répétons ce calcul de manière holographique. Nous montrons que ces deux méthodes de calcul donnent le même résultat, si du côté théorie des champs les conditions aux bords préservent la moitié de la supersymétrie et que du côté gravité l’extension du bord dans le bulk est une surface minimale. / The entanglement entropy has had a tremendous and profound impact on theoretical physics, particularly since the last decade. First introduced in an attempt to explain black holes entropy, it has then found applications in a wide range of research areas, from condensed matter physics to quantum gravity, from quantum information to quantum field theory. In this exciting scientific context, the entanglement entropy has thus emerged as a useful and pivotal tool, and as such justifies the need to be intensively studied. At the heart of this thesis therefore lies the desire to better understand the entanglement entropy. Interesting developments during the recent years concern the boundary effects on the entanglement entropy. This dissertation proposes to explore the question of how the presence of spacetime boundaries affects the entropy, specifically in situations where the entangling surface intersects these boundaries. We present explicit calculations of entanglement entropy in flat spacetime with plane boundaries. We show that boundary induced terms appear in the entropy and we emphasize the prominent role of the boundary conditions. We then study the boundary contribution to the logarithmic term in the entanglement entropy in three and four dimensions. We perform the field theoretic computation of this boundary term for the free N = 4 super-gauge multiplet and then repeat the same calculation holographically. We show that these two calculations are in agreement provided that on the field theory side one chooses the boundary conditions which preserve half of the full supersymmetry and that on the gravity side the extension of the boundary in the bulk is minimal.

In this dissertation I analyze Sir Arthur Eddington's statistical theory as developed in the first six chapters of his posthumously published Fundamental Theory. In particular I look at the mathematical structure, philosophical implications, and relevancy to modern physics. This analysis is the only one of Fundamental Theory that compares it to modern quantum field theory and is the most comprehensive look at his statistical theory in four decades. Several major insights have been made in this analysis including the fact that he was able to derive Pauli's Exclusion Principle in part from Heisenberg's Uncertainty Principle. In addition the most profound general conclusion of this research is that Fundamental Theory is, in fact, an early quantum field theory, something that has never before been suggested. Contrary to the majority of historical reports and some comments by his contemporaries, this analysis shows that Eddington's later work is neither mystical nor was it that far from mainstream when it was published. My research reveals numerous profoundly deep ideas that were ahead of their time when Fundamental Theory was developed, but that have significant applicability at present. As such this analysis presents several important questions to be considered by modern philosophers of science, physicists, mathematicians, and historians. In addition it sheds new light on Eddington as a scientist and mathematician, in part indicating that his marginalization has been largely unwarranted.

Submitted by Vasti Diniz (vastijpa@hotmail.com) on 2017-09-18T14:40:44Z No. of bitstreams: 1 arquivototal.pdf: 5994670 bytes, checksum: 2dd7a3577c0cc6ee44dd8eb7435dfaaf (MD5) / Made available in DSpace on 2017-09-18T14:40:44Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 5994670 bytes, checksum: 2dd7a3577c0cc6ee44dd8eb7435dfaaf (MD5) Previous issue date: 2015-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this thesis we study the dynamics of charge carriers, and the electronic properties, of the C60 fullerene molecule. Characterizing it by a geometric bias. In inertial reference systems and when we have your material under rotation content. Initially we discussed the scientific advent of carbon allotropes, and the importance of modelling its derivates at low energies. We show that at low energies, the graphene - the two-dimensional carbon allotrope form - can be described for a non-massive theory of free fermions. At a second moment, we extended the nonmassive free fermions theory for the C60 molecule. Assuming the hexagonal graphene network can be entered in fullerene when we introduce topological defects. A brief study of topological defects in condensed matter was done. And soon after, we made a description these defects via a non-Euclidean geometry. Showing how the charge carriers in the network see the defects like gauge fields. Then we began to expose the results of this thesis. First we assume the fullerene by a two-dimensional spherical metric with defects, containing a fictitious t’Hooft-Polyakov monopole in its center. TheC60 is still subjected to the action of an Aharonov-Bohm flux arising of a magnetic wire running through its poles. So we get the spectrum, and the prediction of a persistent current in the molecule. Finally we return to the analysis of the molecule, now with your content of matter under rotation. For this, we studied a metric Gödel-type with spherical symmetry. We discussed the problem of causality and obtain the spectrum and the persistent current in terms of the vorticity (W) of spacetime. / Nesta tese estudamos a dinâmica de portadores de carga, e as propriedades eletrônicas, na molécula de fulerenoC60. Caracterizando-a por um viés geométrico. Tanto em sistemas de referência inercial, como quando temos seu conteúdo de matéria sob rotação. Inicialmente abordamos o advento científico das formas alotrópicas do carbono e a importância da modelagem a baixas energias dos seus derivados. Onde mostramos que no limite de baixas energias, o grafeno - que trata-se da forma alótropica bidimensional do carbono - pode ser descrito por uma teoria de férmions livres sem massa. Num segundo momento estendemos a teoria de férmions não massivos para a molécula de C60. Assumindo que a rede hexagonal do grafeno pode inscrever o C60 ao introduzirmos alguns defeitos topológicos. Um breve estudo sobre os defeitos topológicos na matéria condensada foi feito. Onde, logo em seguida, partimos para uma descrição de tais defeitos via uma geometria não-euclidiana. Mostrando como os portadores de carga no meio enxergam os defeitos como campos de gauge. Em seguida começamos a expor os resultados desta tese. Primeiramente assumimos tratar o fulereno por uma métrica de uma esfera bidimensional com defeitos, e contendo um monopolo de t’Hooft-Polyakov fictício em seu centro. O C60 é ainda submetido a ação de um fluxo de Aharonov-Bohm advindo de uma corda magnética quiral transpassando seus polos. Obtemos assim o espectro e a predição de uma corrente persistente na molécula. Por fim retomamos a análise da molécula, agora com seu conteúdo de matéria sob rotação. Para isso assumimos tratar o fulereno por uma métrica do tipo Gödel com simetria esférica. Discutimos o problema da causalidade e obtemos espectro e corrente persistente em termos da vorticidade (W) do espaço-tempo.