Doutorado em Física
URI Permanente para esta coleção
Nível: Doutorado
Ano de início: 2003
Conceito atual na CAPES: 4
Ato normativo: Parecer CES/CNE nº 487/2018, homologado pela Port. MEC 609, publicado no DOU em 18/03/2019.
Periodicidade de seleção: Semestral
Área(s) de concentração: Física
Url do curso: https://fisica.ufes.br/pt-br/pos-graduacao/PPGFis/detalhes-do-curso?id=1509
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Navegando Doutorado em Física por Autor "Alvarenga, Flávio Gimenes"
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- ItemA Quantização da Gravitação em 3D com Constante Cosmológica Positiva(Universidade Federal do Espírito Santo, 2012-07-31) Almaraz, Zui Agustin Oporto; Constantinidis, Clisthenis Ponce; Piguet, Olivier; Vanzella, Daniel Augusto Turolla; Ribeiro, Maria Cristina Batoni Abdalla; Alvarenga, Flávio Gimenes; Gomes, Jose Francisco; Gonçalves, Sergio Vitorino de BorbaIt was shown by Bonzom and Livine that 2+1 gravity with cosmological constant contains an ambiguity that depends on a Barbero–Immirzi-like parameter ? known from 4D gravity. Based on this fact, we showed that, for the ? > 0 case, the Lorentzian theory can be partially reduced, thanks to a suitable gauge fixing, to a Chern–Simons theory with compact gauge group SU(2). Then we revised already known loop quantization of Chern–Simons theory for the case of a space with the topology of a cylinder. Finally we construct a quantum observable which, despite having a not trivial spectrum at the quantum level, it corresponds to a classical quantity identically null.
- ItemBuracos negros fantasmas.(Universidade Federal do Espírito Santo, 2010-04-23) Rodrigues, Manuel Eleuterio; Fabris, Júlio César; Alvarenga, Flávio Gimenes; Mello, Eugênio Ramos Bezerra de; Piguet, Olivier; Sotomayor, Patrício Anibal LetelierWe obtain the general solution of the Einstein-(anti) Maxwell-(anti) Dilaton (EMD)theory for a static, spherically symmetric spacetime in four dimensions. In the phantom(anti) cases, we obtain new solutions with non-degenerate horizon and make the analysis oftheir causal structures. The causal structures of some solutions are exotics, some of themcan not be described in two-dimensional usual Penrose diagrams. We obtain also, usingthe method of Sigma model, new stationary solutions with axial symmetry, for Einstein-anti-Maxwell-Dilaton (E ¯MD) and Einstein-anti-Maxwell-Dilaton-Axion (E ¯MDA) theory.We analyse the causal structure of these new solutions.
- ItemCosmologia Quântica com Vácuo Dinâmico em um Cenário de Comprimento Mínimo.(Universidade Federal do Espírito Santo, 2021-03-16) Gusson, Michael França; Nogueira, José Alexandre; https://orcid.org/0000-0003-0808-6235; http://lattes.cnpq.br/6774401855734421; https://orcid.org/0000-0001-7890-0947; http://lattes.cnpq.br/8375455601973289; Fabris, Julio Cesar; https://orcid.org/000000018880107X; http://lattes.cnpq.br/5193649615872035; Lemos, Nivaldo Agostinho; https://orcid.org/0000-0002-2386-1247; http://lattes.cnpq.br/6802059980173428; Velten, Hermano Endlich Schneider; https://orcid.org/0000000251557998; http://lattes.cnpq.br/0282590467459210; Dilem, Bernardo Brunoro; https://orcid.org/0000-0002-9403-6148; http://lattes.cnpq.br/3281142689535139; Alvarenga, Flávio Gimenes; https://orcid.org/0000-0002-7579-9561; http://lattes.cnpq.br/7169430092692431Theories that propose the unification of general relativity and quantum mechanics, for example the String Theory, point to the existence of a minimum value of observable length. The existence of this implies a generalization of the Heisenberg’s uncertainty principle, so as to no more admit a null uncertainty in position, thus modifying the algebra of quantum mechanics. According to the cosmological model of the Big Bang, the Universe is expanding, which it means that it was very small in the past, so its nature was fundamentally quantum. Thus, it is necessary to build a quantum description of the evolution of the Universe, under the context of modified algebra due to the existence of a minimum length. In this work, was considered the effects in a dynamic vacuum cosmological model, due to the presence of a minimum length introduced by a GUP (generalized uncertainty principle) related to the modified commutation relation [x, p] = ih/1−βP2 . The wave function of the Universe, which is the solution of the Wheeler-DeWitti equation in the representation of the quasiposition space, was found at the limit for small values of the scale factor.
- ItemPadrões de difração de elétrons com e sem efeito de fase Aharonov-Bohm e a divergência em sua forma assintótica.(Universidade Federal do Espírito Santo, 2019-05-30) Favarato, Cássio Cecato; Lima, Denise Assafrão; Gonçalves, Sérgio Vitorino de Borba; Mota, Vinícius Cândido; Alvarenga, Flávio Gimenes; Scopel, Wanderlã Luis; Rojas Leyva, Moises PorfirioIt is common during undergraduate courses to study the phenomenon of diffraction of electromagnetic waves by single and double slit systems via scalar diffraction theory and the Kirchoff integral. Alternatively to this, in this thesis, we analyzed the electron diffraction and interference patterns, via Feynman path integrals. For this, we start from the conceptual model, as originally proposed by RPFeynman in Quantum Mechanics and Path Integrals but which, over time, has been treated more rigorously by other authors, and with greater sophistication and clarity by M.Beau in Feynman path integral approach to electron diffraction for one and two slits: analytical results. At first, we preserve all the analysis given by this author to the problem, with some notes about probable misconceptions and construct the free propagators and wave functions for each stage of the movement for the different systems studied. H. Yabuki, in Feynman Path Integrals in the Young Double-Slit Experiment, makes it clear that in the employed representation, despite being able to extract information about the most diverse possible trajectories, the probabilistic weight of events as loops are relatively negligible, validating the superposition principle as the sum of the emerging wave functions of each slot region. From this we obtain the expression that takes the electronic distributions on the screen. By means of the variation of parameters, such as the geometric and Fresnel number contained in it, the different regimes of the optics appear: Fraunhouffer, Intermediate and Fresnel. Therefore, it was realized that these regimes could be recovered through special conditions conferred the asymptotic forms of Fresnel functions. We extend these arguments to the expression that leads to the electronic distribution with Aharonov-Bohm (AB) phase effect. Throughout a succession of approximations, we reached an expression with physical meaning and the existence of other mathematical expressions that carried divergences in their domains, corroborating the inexistence of an analogous expression to that typical of the regime of Fraunhoffer with mixed phase, that manifests the asymmetries AB. Finally, we demonstrate the emergence of the Berry phase and its relation to the AB phase.
- ItemProbabilidade de tunelamento quântico para o surgimento de um universo clássico preenchido com gás de Chaplygin e poeira(Universidade Federal do Espírito Santo, 2023-03-14) Rocha, Nathália Mattos Novaes da; Goncalves, Sergio Vitorino de Borba; https://orcid.org/0000000285709750; http://lattes.cnpq.br/4992784379693871; https://orcid.org/0000000345816364; http://lattes.cnpq.br/5376461651668363; Ribeiro, Andre Luis Batista; https://orcid.org/0000-0002-3813-2565; http://lattes.cnpq.br/3417734567782570; Alvarenga, Flávio Gimenes; http://lattes.cnpq.br/7169430092692431; Silva, Eduardo Vasquez Corrêa; https://orcid.org/0000-0003-3866-8105; http://lattes.cnpq.br/0541169610474136; Constantinidis, Clisthenis Ponce; http://lattes.cnpq.br/1328163673123152; Oliveira Neto, Gil deThe present work aims to analyze the quantum dynamics contained in the Planck era of the Universe, its emergence mechanism for the inflationary phase and its classical dynamics in a homogeneous and isotropic model, composed of a perfect fluid in the form of dust and a Chaplygin gas. The analysis was carried out through probabilistic calculations of quantum tunneling of a numerical model quantized by the Crank-Nicolson method, whose calculations were performed in terms of the model parameters. The results show a greater susceptibility for the classical emergence of a Universe filled with dust and Chaplygin gas, when compared to results found in the literature for a model in which the Universe is filled with Chaplygin gas and radiation.