https://repositorio.ufpb.br/jspui/handle/tede/5435 PPGF 2026-04-22T22:43:52Z https://repositorio.ufpb.br/jspui/handle/123456789/37676 Título: Influência conjunta da polarização e da coerência da luz no experimento da dupla fenda sob uma perspectiva quântica Autor(es): Barbosa, Natália Érika Laurentino Orientador: Bernardo, Bertúlio de Lima Abstract: In this research, we studied the wave-particle duality through quantifiers of visibility and distuinguishability by the complementary principle. We used the unified density matrix formalism of coherence and polarization as the basis for this study. If we have information on the path, the interference pattern is destroyed and the photon behaves like a particle, on the other hand, a maximum contrast pattern is verified when there is no information on the path taken, a wave-like behavior. To witness the wave-particle duality using the visibility V and distinguishability D quantifiers derived in the research, we present several physical examples and show that it is possible to verify the behavior of photons, quantified through the principle of complementarity by means of the inequality D2 + V 2 ≤ 1. Editor: Universidade Federal da Paraíba Tipo: Dissertação 2020-07-29T00:00:00Z https://repositorio.ufpb.br/jspui/handle/123456789/37429 Título: Modelos generalizados de Chern-Pontryagin e uma nova teoria de espinores não-locais Autor(es): Silva, Ramires Nascimento da Orientador: Silva, Paulo José Ferreira Porfírio da Abstract: This thesis discusses modified theories of gravitation, exploring aspects inherent to causality, unitarity, renormalizability, Lorentz invariance and CPT symmetry breaking, with emphasis on the original results extracted from two new categories of models: i) generalized Chern- Pontryagin gravity models; and ii) the non-local spin-1/2 field model, in Minkowski space. In the first case, we formulate a new class of modified gravity models in 4 dimensions, whose action is characterized by an arbitrary function of the Ricci scalar and the topological Chern-Pontryagin term ∗RR. Within this framework, we derive the gravitational field equations and solve them for a particular model fI (R, ∗RR) = R+β(∗RR)2 and fII(R, ∗RR) = R + αR2 + β(∗RR)2, considering two ansatzes: the slowly rotating Schwarzschild metric and first-order perturbations of Gödel-type metrics. For the former, considering slowly rotating Schwarzschild metric, we find a first-order correction to the frame dragging effect boosted by the parameter L, which characterizes the departures from general relativity results. We show that generalized four-dimensional Chern-Pontryagin models admit a scalar-tensor representation, whose explicit form presents two scalar fields: Φ, a dynamical degree of freedom (scalaron). In contrast, the second, ϕ, is a non-dynamical degree of freedom, which arises coupled with the Chern-Pontryagin topological term ∗RR, that is, ϕ ∗RR, which is nothing more than the gravitational Chern-Simons term. In the latter model, we create a novel nonlocal spin-1/2 field theory in which the form factors depend on the Dirac operator rather than on the d’Alembert operator. At the classical level, we investigate the dispersion relation of free spin-1/2 particles and find that it increasingly deviates from the standard case as the nonlocal effects become relevant. At the quantum level, we compute the fermionic one-loop effective action for the nonlocal spin-1/2 theory with Yukawa coupling and show that the contributions of nonlocal effects are significant in the UV limit. At the same time, in the IR they are suppressed by a UV cutoff scale, which has been chosen to coincide with the nonlocality scale Λ. We minimally couple a U(1) gauge field to the non-local spin-1/2 field theory and explicitly demonstrate that this theory is gauge invariant. Finally, we obtain a nonlocal version of the Pauli equation and the impact of the nonlocality on the gs-factor of massive particles. Editor: Universidade Federal da Paraíba Tipo: Tese 2025-08-29T00:00:00Z https://repositorio.ufpb.br/jspui/handle/123456789/37423 Título: Um estudo do desvio da luz no formalismo de campo forte Autor(es): Moreira, Antonio Lucas Araujo Orientador: Nascimento, José Roberto Soares do Abstract: In this master thesis, we work out light deflection using the strong field approach and apply the results in the study of gravitational lensing. This formalism becomes useful when the light gets close to a photon sphere, where null geodesics trace circular orbits. In this limit, the impact parameter of the photon approaches the critical impact parameter, and if it is less than that the photon falls into the event horizon. We start assuming a static, spherically symmetric and asymptotically flat metric and then we apply this formalism to the Schwarzschild, Reissner-Nordström and black-bounce metrics. In the strong field limit, the integral for the light deflection diverges, so that we have to extract the divergent term and express the result in terms of some parameters. Ultimately, we define observables in the context of gravitational lensing with the purpose of distinguishing between those metrics from future experimental data. Editor: Universidade Federal da Paraíba Tipo: Dissertação 2023-07-26T00:00:00Z https://repositorio.ufpb.br/jspui/handle/123456789/37183 Título: Gravitação Invariante de Weyl: teoria e aplicações Autor(es): Duarte, Mauro Parnaiba Orientador: Romero Filho, Carlos Augusto Abstract: The present thesis is dedicated to the study of the Weyl Invariant Gravitational Theory, a modification and reinterpretation of the original theory proposed by Hermann Weyl. Initially, we present in detail the construction of Weyl’s theory. Next, we develop a gauge-invariant for- mulation for the unified theory of Weyl. This formulation consists of a proposal that renders both the metric tensor and the Weyl field invariant quantities under gauge transformations. With this, it is possible to construct a gauge-invariant proper time definition, in addition to allowing the description of the coupling between geometric fields and matter. In this way, we obtain a new alternative theory of gravitation. An important aspect emphasized in the thesis is that the Weyl geometric 1-form can be formally interpreted as a massive vector field, which refers us to the theory proposed in 1936 by the Romanian physicist Alexandru Proca, who aimed to describe the interaction and dynamics of massive spin-1 bosons. As an application of the field equations of the Weyl invariant theory, we investigate a solution in the weak-field regime. Furthermore, we study in detail the propagation of gravitational waves in this new modified theory of gravity. Finally, we propose an alternative approach to the problem of the origin of dark matter. We show that, for appropriate values of the free parameter of the adopted model, the Weyl field, during the matter-dominated, era, exhibits the expected behavior for a dark matter candidate. Editor: Universidade Federal da Paraíba Tipo: Tese 2025-08-22T00:00:00Z