O objeto de estudo desta dissertação é o efeito de criação de partículas pela curvatura sob o escopo de uma teoria de espalhamento, discutindo quando que a interpretação a partir de uma matriz S é tangível e obtendo sua expressão nesses casos. O capítulo de introdução aborda superficialmente conceitos de relatividade geral e de teoria quântica de campos em espaços planos e curvos, necessários para a construção da matriz S. O conteúdo deste capítulo segue as apresentações feitas por Wald, Parker e Birrell em geral, tendo como guia as obras de Bar, Wald e Hawking no que se trata especificamente de relatividade geral, e de Penrose e Rindler no que se trata da estrutura espinorial. A construção da matriz S se dá no capítulo 2, tendo como guia o trabalho de Wald. O capítulo 3 apresenta exemplos que permitem a contextualização da criação de partículas em casos específicos de espaços-tempos em expansão. Este estudo nos permite verificar que as condições que precisam ser satisfeitas em um espaço-tempo globalmente hiperbólico e assintoticamente estacionário para que a formulação da matriz S possa ser feita são que as teorias no passado e futuro distantes devem ser unitariamente equivalentes, que a relação entre as regiões se dá através de transformações de Bogolyubov dadas por operadores limitados definidos em toda a parte e que tais operadores satisfaçam a condição de Hilbert-Schmidt. Nestes casos obtemos uma expressão para a matriz $S$ que descreve a criação de partículas pela curvatura do espaço-tempo para o campo de Klein-Gordon e de Dirac, além de outras relações úteis, como número médio de partículas criadas e probabilidade de se encontrar partículas em determinado modo, o que permite uma analogia com a radiação de corpo negro, passo fundamental para se entender fenômenos de grande interesse na física, como a radiação de Hawking e a criação de partículas no período inflacionário. / This master\'s thesis deals with the effect of particle creation by the curvature of space-time according to the point of view of scattering theory, discussing when such interpretation is possible by means of an S-matrix and obtaining its expression in those cases. The first chapter treats, superficially, some concepts of general relativity and quantum field theory in plane and curved space-times that are imperative to understand the construction of the S-matrix. The subject of this chapter is covered in the work of Wald, Parker, and Birrell, and follows closely the work of Bar, Wald and Hawking, when treats concepts specifically from general relativity, and from Penrose and Rindler, when talking about the spinor structure of space-time. The construction of the S-matrix is made in the second chapter, along the lines of the work of Wald. The third chapter presents some examples that bring some light on the creation of particles in specific cases of expanding space-times. This study let us verify that an S-matrix formulation is tenable, on globally hyperbolic asymptotic stationary curved space-times, if both quantum theories in the distant past and distant future are unitary equivalent, the relation of both regions is made by Bogolyubov transformations by means of everywhere defined bounded operators and that those operators satisfy the Hilbert-Schmidt condition. In those cases we derive the expression of the S-matrix for the Klein-Gordon and Dirac fields. Also we obtain the number of particles created and the probability of find particles in a particular mode, with let one make an analogy with the black body radiation, which is a fundamental step in the direction of understanding interesting phenomena in quantum field theory in curved space-times, like the Hawking radiation and particle creation in the early universe.

Nesta tese estudamos o modelo CP^(N-1) em (2+1) dimensões do espaco-tempo, onde o campo básico está na representacão fundamental. Diferentemente do caso em que o campo básico está na representacão adjunta, já estudado na literatura, o modelo por nós estudado se reduz ao modelo supersimétrico usual no limite comutativo. Analisamos a estrutura de fase e calculamos as correcões dominantes e subdominantes na expansão 1/N. Provamos que a teoria é livre de singularidades infravermelhas não integráveis e é renormalizável na ordem dominante. A funcão de vértice de dois pontos do campo básico é calculada e renormalizada de uma forma explicitamente supersimétrica na ordem subdominante. / In this thesis we sutudy the noncommutative supersymmetric CP^(N-1) model in (2+1) space-time dimensions, where the basic field is in the fundamental representation which, differently to the adjoint representation already studied in the literature, goes to the usual supersymmetric model in the commutative limit. We analyse the phase structure of the model and calculate the leading and subleading corrections in the 1/N expansion. We prove that the theory is free of non-integrable IR/UV infrared singularities and is renormalizable in the leading order. The two point vertex function of the basic field is also calculated and renormalized in an expliciitly supersymmetic way up to subleading order.

Orientador: Prof. Dr. André Gustavo Scagliusi Landulfo / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Física, 2017. / A descoberta do comportamento termodinâmico de buracos negros no contexto da teoria quântica de campos em espaços-tempos curvos deu origem a diversas questões, dentre elas onde estão e quais são os graus de liberdade associados a entropia dos mesmos. Nessa dissertação estudamos esse tópico propondo que, se não toda, alguma parte desta entropia é devida ao emaranhamento entre os graus de liberdade, internos e externos ao buraco, dos campos quânticos presentes no espaço-tempo. / The discovery of thermodynamic behavior of black holes in the context of quantum field theory in curved spacetimes has given rise to several issues, among them where and what are the degrees of freedom associated to their entropy. In this dissertation we study this topic proposing that, if not all, some of this entropy is due to the entanglement between degrees of freedom, internal and external to the hole, of quantum fields present in the spacetime.

Orientador: Prof. Dr. André Gustavo Scagliusi Landulfo / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Física, Santo André, 2018. / Nas últimas décadas, pesquisas na área de física de buracos negros mostraram que existe uma relação profunda entre buracos negros, termodinâmica e mecânica quântica. Em particular, buracos negros em um contexto semiclássico parecem possuir uma temperatura TH=k/2p e uma entropia Sbh =A/4, proporcionais à sua gravidade superficial k e à sua área A, respectivamente. Essa surpreendente conexão é reforçada ao analisarmos a validade da chamada Segunda Lei Generalizada da Termodiâmica (SLG), que afirma que a entropia da matéria fora do buraco negro somada à entropia do buraco negro nunca decresce com o tempo. Este trabalho investiga provas gerais da validade da Segunda Lei Generalizada, já que tem um papel central na interpretação de buracos negros como entidadestermodinâmicas. Emseguida, é analisado como podemos usar a SLG para extender um teorema clássico de singularidade para um contexto semiclássico. / In the past few decades, research in black hole physics have shown a deep relation between black holes, thermodynamics, and quantum mechanics. In particular, blackholes in a semiclassical context appear to have a temperatureTH =k/2p and an entropy Sbh = A/4 proportional to its surface gravity k and area A,respectively. This striking connection is strengthened when one analyses the validity of the so called Generalized Second Law of Thermodynamics (GSL), which states that the entropy of matter outside the black hole plus the black hole¿s entropy never decrease with time. This work investigate general proofsofthevalidityofGeneralizedSecondLaw,sinceitplaysacentralroleininterpreting black holes as thermodynamical entities. In addition, it is analyzed how the GSL can be used to extend a classical singularity theorem to a semiclassical context.

Nesta tese de doutorado é utilizado o método das Regras de Soma da QCD para estudar a natureza dos novos estados ressonantes do charmonium: Y(3930), Y(4140), X(4350), Y(4260), Y(4360) e Y(4660). Há fortes evidências de que estes estados possuam estruturas hadrônicas não convencionais (ou exóticas) uma vez que as suas respectivas massas e canais de decaimento observados experimentalmente são inconsistentes com o que é esperado para o estado ressonante convencional do charmonium, J/psi. O mesmo fenômeno ocorre no setor do bottomonium, onde os novos estados Yb(10890) e Yb(11020) observados recentemente poderiam indicar a existência de novos estados exóticos do bottomonium. Neste sentido, verifica-se que o estado Y(4140) poderia ser descrito ou por uma estrutura molecular Ds*Ds* (0++) ou mesmo uma mistura entre estados moleculares Ds*Ds* (0++) e D*D* (0++). Já os estados Y(3930) e o X(4350) não podem ser descritos por correntes moleculares D*D* (0++) e Ds*Ds* (1-+), respectivamente. Verifica-se também que a estrutura molecular Psi(2S) f_0(980) (1--) descreve muito bem a massa do estado Y(4660). Uma extensão ao setor do bottomonium indica que o estado molecular Y(2S) f_0(980) é um bom candidato para descrever a estrutura do estado Yb(10890). É feita também uma estimativa para os possíveis estados moleculares formados por mésons D(*) e B(*), que poderão ser observados em futuros experimentos realizados pelo LHC. Um amplo estudo, utilizando o formalismo das Regras de Soma e também da Dupla Razão das Regras de Soma, é feito para calcular as massas dos bárions pesados na QCD. As estimativas para as massas dos bárions com um (Qqq) e com dois (QQq) quarks pesados são um excelente teste para a capacidade do método das regras de soma em prever a massa dos bárions que ainda não foram observados. / In this thesis, the QCD sum rules approach was used to study the nature of the new charmonium resonances: Y(3930), Y(4140), X(4350), Y(4260), Y(4360) and Y(4660). There is a strong evidence that these states have non-conventional (or exotic) hadronic structures since their respective masses and decay channels observed experimentally are inconsistent with what expected for a conventional charmonium state, J/psi. The same phenomenon occurs on the bottomonium sector, where new states like Yb(10890) and Yb(11020) observed recently could indicate the existence of new bottomonium exotic states. In this way, one verifies that the state Y(4140) could be described as a Ds*Ds* (0++) molecular state or even as a mixture of Ds*Ds* (0++) and D*D* (0++) molecular states. For the Y(3930) and X(4350) states, both cannot be described as a D*D* (0++) and Ds*Ds* (1-+), respectively. From a sum rule point of view, the Y(4660) state could be described as a Psi(2s) f_0(980) (1--) molecular state. The extension to the bottomonium sector is done in a straightforward way to demonstrate that the Y(2S) f_0(980) molecular state is a good candidate for describing the structure of the Yb(10890) state. In the following, one estimates the mass of the exotic Bc-like molecular states using QCD Sum Rules - these exotic states would correspond to bound states of D(*) and B(*) mesons. All of these mass predictions could (or not) be checked in a near future experiments at LHC. A large study using the Double Ratio of Sum Rules approach has been evaluated for the study of the heavy baryon masses in QCD. The obtained results for the unobserved heavy baryons, with one (Qqq) and two (QQq) heavy quarks will be an excellent test for the capability of the sum rule approach in predicting their masses.

Le schéma de régularisation de Taylor-Lagrange (TLRS) est basé sur la définition des champs en tant que distributions à valeurs d'opérateurs (OPVD). L'expression de ces OPVD implique des fonctions test qui, grâce à leurs propriétés (propriétés d'échelles, super-régularité), permettent d'étendre des distributions singulières à tout l'espace. Ce type de régularisation, que l'on peut qualifier de coupure ultra-douce, est efficace quelque soit le degré de divergence originel et produit des amplitudes finies dépendant d'une échelle intrinsèque sans dimensions. Enfin, ce schéma préserve les symétries du groupe de Poincaré et l'invariance de jauge. Après avoir présenté le formalisme TLRS, celui-ci est appliqué au calcul des corrections radiatives en QED ainsi qu'à celles à la masse du boson de Higgs dans le cadre du modèle standard de la physique des particules. Dans une dernière partie, il est appliqué au modèle de Yukawa dans le cadre de la dynamique sur le front de lumière. Les corrections radiatives et un calcul non-perturbatif d'états liés sont effectués. Ces exemples permettent de vérifier, d'une part, l'applicabilité de ce schéma dans différents cas, et d'autre part, de tester son respect des propriétés de symétrie des théories. / The Taylor-Lagrange regularization scheme (TLRS) is based on the definition of fields as operator valued distributions (OPVD). The expression of these OPVDs implies test functions which, thanks to their properties (scaling properties, super-regularity), allow to extend singular distributions to the whole space. This type of regularization, which could be qualified as an ultra-soft cut-off, is efficient for any order of divergences and produces finite amplitudes depending on an intrinsic dimensionless scale. Finally, this scheme respects the Poincaré group symmetries as well as gauge invariance. After an introduction to the TLRS, it is applied to the calculation of radiative corrections to QED and to the mass of the Higgs boson within the standard model of particle physics. In a last section, it is applied to the Yukawa model using the framework of light front dynamics. Radiative corrections and non-perturbative bound state are calculated. This examples allow to verify, on one hand, the applicability of the TLRS, and on the other hand to test its respect of the symmetry properties of the theories.

I defend three general claims concerning inter-theoretic reduction in physics. First, the popular notion that a superseded theory in physics is generally a simple limit of the theory that supersedes it paints an oversimplified picture of reductive relations in physics. Second, where reduction specifically between two dynamical systems models of a single system is concerned, reduction requires the existence of a particular sort of function from the state space of the low-level (purportedly more accurate and encompassing) model to that of the high-level (purportedly less accurate and encompassing) model that approximately commutes, in a specific sense, with the rules of dynamical evolution prescribed by the models. The third point addresses a tension between, on the one hand, the frequent need to take into account system-specific details in providing a full derivation of the high-level theory’s success in a particular context, and, on the other hand, a desire to understand the general mechanisms and results that under- write reduction between two theories across a wide and disparate range of different systems; I suggest a reconciliation based on the use of partial proofs of reduction, designed to reveal these general mechanisms of reduction at work across a range of systems, while leaving certain gaps to be filled in on the basis of system-specific details. After discussing these points of general methodology, I go on to demonstrate their application to a number of particular inter-theory reductions in physics involving quantum theory. I consider three reductions: first, connecting classical mechanics and non-relativistic quantum mechanics; second,connecting classical electrodynamics and quantum electrodynamics; and third, connecting non-relativistic quantum mechanics and quantum electrodynamics. I approach these reductions from a realist perspective, and for this reason consider two realist interpretations of quantum theory - the Everett and Bohm theories - as potential bases for these reductions. Nevertheless, many of the technical results concerning these reductions pertain also more generally to the bare, uninterpreted formalism of quantum theory. Throughout my analysis, I make the application of the general methodological claims of the thesis explicit, so as to provide concrete illustration of their validity.

La position centrale occupée par les Théories Quantiques des Champs Topologiques (TQFTs) dans l’étude de la topologie en basse dimension est due à leur structure extraordinairement riche, qui permet différentes interactions et applications à des questions de nature géométrique. Depuis leur première apparition, un grand effort a été mis dans l’extension des invariants quantiques de 3-variétés en TQFTs et en TQFT Étendues (ETQFTs). Cette thèse s’attaque à ce problème dans deux cadres généraux différents. Le premier est l’étude des invariants quantiques semi-simples de Witten, Reshetikhin et Turaev issus de catégories modulaires. Bien que les ETQFTs correspondantes étaient connues depuis un certain temps, une réalisation explicite basée sur la construction universelle de Blanchet, Habegger, Masbaum et Vogel apparaît ici pour la première fois. L’objectif est de tracer la route à suivre dans la deuxième partie de la thèse, où la même procédure est appliquée à une nouvelle famille d’invariants quantiques non semi-simples due à Costantino, Geer et Patureau. Ces invariants avaient déjà été étendus en TQFTs graduées par Blanchet, Costantino, Geer and Patureau, mais seulement pour une famille explicite d’exemples. Nous posons la première pierre en introduisant la définition de catégorie modulaire relative, un analogue non semi-simple aux catégories modulaires. Ensuite, nous affinons la construction universelle pour obtenir des ETQFTs graduées étendant à la fois les invariants quantiques de Costantino, Geer et Patureau et les TQFTs graduées de Blanchet, Costantino, Geer et Patureau dans ce cadre général / The central position held by Topological Quantum Field Theories (TQFTs) in the study of low dimensional topology is due to their extraordinarily rich structure, which allows for various interactions with and applications to questions of geometric nature. Ever since their first appearance, a great effort has been put into extending quantum invariants of 3-dimensional manifolds to TQFTs and Extended TQFTs (ETQFTs). This thesis tackles this problem in two different general frameworks. The first one is the study of the semisimple quantum invariants of Witten, Reshetikhin and Turaev issued from modular categories. Although the corresponding ETQFTs were known to exist for a while, an explicit realization based on the universal construction of Blanchet, Habegger, Masbaum and Vogel appears here for the first time. The aim is to set a golden standard for the second part of the thesis, where the same procedure is applied to a new family of non-semisimple quantum invariants due to Costantino, Geer and Patureau. These invariants had been previously extended to graded TQFTs by Blanchet, Costantino, Geer an Patureau, but only for an explicit family of examples. We lay the first stone by introducing the definition of relative modular category, a non-semisimple analogue to modular categories. Then, we refine the universal construction to obtain graded ETQFTs extending both the quantum invariants of Costantino, Geer and Patureau and the graded TQFTs of Blanchet, Costantino, Geer and Patureau in this general setting

Orientador: Julio Marny Hoff da Silva / Resumo: Teorias que violam as simetrias de Lorentz são de certa forma comumente encontradas na literatura. Com o estudo dos subgrupos do grupo de Lorentz, uma pergunta fica no ar. Será preciso todo o grupo de Lorentz para descrever as simetrias do espaço-tempo ou apenas um subgrupo já seria suficiente? Se isso for possível teríamos um teoria que violaria as simetrias de Lorentz e consequentemente outras peguntas surgem. Essa teoria serve para descrever a matéria bariônica ou outro tipo de matéria? Neste trabalho usaremos os grupos da very special relativity (VSR) que são subgrupos do grupo de Lorentz e tentaremos responder essas perguntas com base em cálculos e em experimentos largamente difundidos na literatura: o experimento de Michelson-Morley e o fenômeno da precessão de Thomas. Também discutiremos algumas consequências advindas de uma teoria quântica de campos que viola as simetrias de Lorentz. / Mestre

This is a diploma thesis on Buchdahl's equations for the description of massive particles of arbitrary spin s/2. On 4-dimensional, globally hyperbolic Lorentzian spacetime manifolds, existence of advanced and retarded Green's operators is proved, the Cauchy problem for Buchdahl's equations is solved globally and two possible constructions for quantizing Buchdahl fields using CAR algebras in the fashion of [Dimock 1982] are given.