Thesis (Ph.D.)--Victoria University of Wellington, 2009. / Includes bibliographical references.

Thesis (M.S.)--Brigham Young University. Dept. of Physics and Astronomy, 2007. / Includes bibliographical references (p. 96-98).

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.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Static, spherically-symmetric particle-like solutions to the coupled Einstein-Dirac and Einstein-Dirac-Maxwell equations have been studied by Finster, Smoller and Yau (FSY). In their work, FSY left the fermion mass as a parameter set to ±1. This thesis generalises these equations to include the Higgs field, letting the fermion mass become a function through coupling, μ. We discuss the dynamics associated with the Higgs field and find that there exist qualitatively similar solutions to those found by FSY, with well behaved, non-divergent metric components and electrostatic potential, close to the origin, going over to the point-particle solutions for large r; the Schwarzschild or Reissner-Nordström metric, and the Coulomb potential. We then go on to discuss an alternative gravity theory, conformal gravity, (CG), and look for solutions of the CG equations of motion coupled to the Dirac, Higgs and Maxwell equations. We obtain asymptotically nonvanishing, yet fully normalisable Dirac spinor components, resembling those of FSY, and, in the case where charge is included, non-divergent electrostatic potential close to the origin, matching onto the Coulomb potential for large r.

The observational approach to cosmology is the endeavour to reconstruct the geometry of the Universe using only data that is theoretically verifiable within the causal boundaries of a cosmological observer. Using this approach, it was shown in [36] that given ideal cosmological observations, the only essential assumption necessary to determine the geometry of the Universe is a theory of gravity. Assuming General Relativity, the full set of Einstein field equations (EFEs) can be used to reconstruct the geometry of the Universe using direct observations on the past null cone (PNC) as initial conditions. Observationally and theoretically this is a very ambitious task and therefore, current developments have been restricted to spherically symmetric dust models while only relaxing the usual assumption of homogeneity in the radial direction. These restricted models are important for the development of theoretical foundations and also useful as verification models since they avoid the circularity of verifying what has already been assumed. The work presented in this thesis is the development of such a model where numerical relativity (NR) is used to simulate the observable universe. Similar to the work of Ellis and co-workers [36], a reference frame based on the PNC is used. The reference frame used here, however, is based on that of the characteristic formalism of NR, which has developed for calculating the propagation of gravitational waves. This provides a formalism that is well established in NR, making the use of existing algorithms possible. The Bondi-Sachs coordinates of the characteristic formalism is, however, not suitable for calculations beyond the observer apparent horizon (AH) since the diameter distance used as a radial coordinate becomes multi-valued when the cosmological PNC reconverges in the history of a universe, smaller in the past. With this taken into consideration, the Bondi-Sachs characteristic formalism is implemented for cosmology and the problem approaching the AH is investigated. Further developments address the limitations approaching the AH by introducing a metric based on the Bondi-Sachs metric where the radial coordinate is replaced with an affine parameter. The model is derived with a cosmological constant Λ incorporated into the EFEs where Λ is taken as a parameter of the theory of gravity rather than as a matter source term. Similar to the conventional characteristic formalism, this model consists of a system of differential equations for numerically evolving the EFEs as a characteristic initial value problem (CIVP). A numerical code implemented for the method has been found to be second order convergent. This code enables simulations of different models given identical data on the initial null cone and provides a method to investigate their physical consistency within the causally connected region of our current PNC. These developments closely follow existing 3D schemes developed for gravitational wave simulations, which should make it natural to extend the affine CIVP beyond spherical symmetric simulations. The developments presented in this thesis is an extended version of two papers published earlier.

Exact solutions to Einstein's field equations in the presence of matter are presented. A one parameter family of interior solutions for a static fluid is discussed. It is shown that these solutions can be joined to the Schwarzschild exterior, and hence represent fluid spheres of finite radius. Contained within this family is a set of solutions which are gaseous spheres defined by the vanishing of the density at the surface. One such solution yields an analytic expression which corresponds to the asymptotic numerical solution of Oppenheimer and Volkoff for the degenerate neutron gas. These gaseous spheres have ratios of specific heats that lie between one and two in the vicinity of the origin, increasing outward, but remaining less than the velocity of light throughout.

MENDES, Wendel Macedo. Localização de Férmions em D dimensões. 2013. 55 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2013. / Submitted by Edvander Pires (edvanderpires@gmail.com) on 2015-10-23T19:20:31Z No. of bitstreams: 1 2013_dis_wmmendes.pdf: 369040 bytes, checksum: cd60b4ab7c07a63351d2b9dd5a277139 (MD5) / Approved for entry into archive by Edvander Pires(edvanderpires@gmail.com) on 2015-10-23T19:38:03Z (GMT) No. of bitstreams: 1 2013_dis_wmmendes.pdf: 369040 bytes, checksum: cd60b4ab7c07a63351d2b9dd5a277139 (MD5) / Made available in DSpace on 2015-10-23T19:38:03Z (GMT). No. of bitstreams: 1 2013_dis_wmmendes.pdf: 369040 bytes, checksum: cd60b4ab7c07a63351d2b9dd5a277139 (MD5) Previous issue date: 2013 / In this work we analyzed the localization of fermions of spin-1/2 in a D-dimensional bulk in a (D-2)-branes scenario. The model used for this is a dimensional extension of models Randall-Sundrum (RS) and thick branes. It is known as co-dimension 1 model. The obtained results are based in no-factorizable geometry type Anti-de Sitter. During the zero mode localization process, it is uses both the Randall-Sundrum metric as a metric with smooth warped factor that depends on the coordinate of extra dimension, frequently used in thick brane models. As the spin-1/2 representations change with dimension of spacetime, the localization process, somehow, must take into account the dimensionality of bulk. Based on these models, one finds that the localization fermions in (D-2)-branes changes when the spacetime is par or odd. They are not located when the dimensionality of bulk is par an only one of chiralities can be located when D is odd. / Nesse trabalho é analizado a localização de férmions de spin 1/2 em um bulk D-dimensional em um cenário de (D-2)-branas. O modelo usado para tal é uma extensão para mais dimesões dos modelos Randall-Sundrum (RS) e de brana espessa. Ele é conhecido como modelo de codimensão 1. Os resultados obtidos são fundamentados em uma geometria não-fatorizável do tipo Anti-de Sitter. Durante o processo de localização do modo zero, usa-se tanto a métrica de Randall-Sundrum como uma métrica com fator de dobra suave que depende da coordenada da dimensão extra, frequentemente usada nos modelos de brana espessa. As representações de spin 1/2 variam com a dimensão do espaço-tempo, então o processo de localização deve levar em conta a dimensionalidade do bulk. Baseados nesses modelos, descobre-se que a localização de férmions em (D-2)-branas muda quando o espaço-tempo é par ou ímpar. Eles não são localizados quando a dimensionalidadedo bulk é par e somente uma das quiralidades pode ser localizada quando D é ímpar.

Made available in DSpace on 2014-06-11T19:32:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-28Bitstream added on 2014-06-13T18:43:08Z : No. of bitstreams: 1 landulfo_ags_dr_ift.pdf: 1384269 bytes, checksum: 63c70f6df185aec50583b1cc399bbf1b (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Mesmo tratando a gravidade classicamente, a Teoria Quântica de Campos em Espaços Tempos Curvos (TQCEC) faz previsões impressionantes sobre o comportamento de campos quânticos na presença de campos gravitacionais. Entretanto, ao mesmo tempo em que nos revela efeitos surpreendentes, a TQCEC levanta uma série de questionamentos. O desenvolvimento de uma teoria na interface entre a teoria da relatividade, a mecânica quântica e a teoria da informação poderá não só lançar uma nova luz em tais questões como também nos permitir descobrir novos efeitos de gravitação quântica de baixas energias. Entretanto, os efeitos que a teoria da relatividade causa na teoria da informação quântica são não triviais já no espaço-tempo de Minkowski. Faz-se necessáaria portanto uma análise cuidadosa de tais efeitos já no contexto da relatividade especial. Sendo assim, estudamos primeiro o comportamento das desigualdades de Bell usando férmions de spin 1/2 e fótons quando os detetores que medem spin e polarização, respectivamente, movemse com certa velocidade. Além disso, usamos o limite de Holevo para estudar sistemas de comunicação quando as partes que trocam informação tem um movimento relativo. Como um desenvolvimento natural, estudamos diversos aspectos da teoria da informação quântica no contexto da teoria quântica de campos e, em particular, do efeito Unruh. Tais resultados nos permitiram prever o comportamento de qubits nas vizinhanças de um buraco negro de Schwarzschild / Although it treats gravity classically, the Quantum Field Theory in Curved Spacetimes (QFTCS) makes remarkable predictions about de behavior of quantum fields in the presence of gravitational fields. However, these striking discoveries raises several issues. The development of a theory at the interface between the theory of relativity, quantum mechanics and information theory could not only shed new light on such questions as well as allow us to uncover new low-energy quantum gravity effects. However, relativity affects quantum information theory in a highly non-trivial way already in Minkowski spacetime. Therefore, a careful analysis of these effects in the context of special relativity is needed. For this purpose, we begin investigating how the movement of the spin and polarization detectors influences the Bell inequalities using spin 1/2 fermions and photons, respectively. Then, we use the Holevo bound to investigate quantum communication channels when the parts that trade information have a relative motion. As a natural development, we use quantum field theory and, in particular, the Unruh effect to analyze several aspects of quantum information theory. This enables us to predict the behavior of qubits in the vicinity of a Schwarzschild black hole

O trabalho propõe a aproximação da educação e da ciência com relação às artes, valorizando assim, nessas áreas, a sensibilidade e a sensorialidade, a criatividade, a dimensão de ruptura com o senso comum, a referência à beleza, à ludicidade e ao prazer. Uma investigação mais teórica dialoga constantemente com e é permeada pelo relato de uma experiência pedagógica desenvolvida no curso de licenciatura em Física do Instituto Federal de Educação, Ciência e Tecnologia de São Paulo - IFSP. Nesta experiência, desenvolvemos um aprofundamento da escuta e do diálogo, verbal e não-verbal, por meio da dinâmica de jogos teatrais, procurando, através desses jogos, tornar mais presente uma dimensão corporal e expressiva em associação com a reflexão sobre o conhecimento físico e sobre a atuação docente. Procuro tecer analogias entre as concepções de espaço e tempo físicos - com ênfase na noção de relatividade - e concepções que podem ser associadas a expressões artísticas e a trabalhos filosóficos e especulativos. A exploração do desenvolvimento histórico dessas concepções, buscando destacar a relação com distintas visões de mundo, pretende alimentar proposições de jogos e atividades pedagógicas que permitam abordar esses temas privilegiando a contextualização cultural e as repercussões no imaginário. / This work proposes a connection between education and science in relation to arts, valuing sensibility and sensory feeling, creativity, the context of bursting the common sense, and the reference to beauty, playfulness and pleasure. A more theoretical investigation constantly interacts with and is permeated by reports of a pedagogical experience developed in the degree course of Physics of the Federal Institute of Education, Science and Technology of São Paulo (Instituto Federal de Educação, Ciência e Tecnologia de São Paulo) - IFSP. In such experience, we have strengthened the hearing and the verbal and non-verbal dialog by means of theater games, aiming at achieving through such games a corporeal and expressive approach in association with the thinking of the physical awareness and the teachers\' action. I intend to draw analogies between the concepts of space and time in physics - emphasizing on the notion of relativity - and concepts that might be associated to artistic expressions and philosophical and speculative works. Seeking to call the attention to the relation with different world-views, the exploration of the historic progress of those concepts envisions to stimulate proposals of games and pedagogic activities that enable the approach to such topics by focusing on cultural context and repercussions on the imaginary.