http://localhost:8080/handle/prefix/51 Tue, 10 Nov 2026 01:38:10 GMT 2026-11-10T01:38:10Z http://localhost:8080/handle/prefix/120 Title: Estudo de um fluído cosmológico com produção de partículas em N dimensões Autor(es): Souza, Rochelle Gomes de Primeiro Orientador: Batista, Miguel Gustavo de Campos Abstract: We study a cosmological model where the number of particles do not conserve in a spacetime with extra dimensions. The open system cosmological model by I. Prigogine considered the particle formation at expenses of the gravitational field with intent to explain the entropic content of the universe, and presently, this model can be an alternative to explain the accelerated expansion of the universe. We generalize the open system cosmological model including an extra dimension and the creation process of particles is due to the compactification of the extra dimension, evolving for the usual quadri-dimensional spacetime. Publisher: Universidade Federal de Roraima Tipo: Dissertação Tue, 01 Jan 2013 00:00:00 GMT http://localhost:8080/handle/prefix/120 2013-01-01T00:00:00Z http://localhost:8080/handle/prefix/29 Title: Gravitacionismo no contexto da teoria gravitacional de Brans-Dicke Autor(es): Silva, João de Ribamar Primeiro Orientador: Barros, Adriano Trindade Abstract: In this work we develop the formalism of the gravitomagnetism in the context of the Brans-Dicke theory of gravity. We write the field equations in a type-Maxwell form while considering the approximations of weak field and of low speed of rotation of the source. We examine the effect of Lense-Thirring precession of inertial frames and obtained the equation of motion for a particle. We have also introduced a model with the angular momentum of the source varying linearly with time, calculating the gravitomagnetic time delay due. The results were compared with the predictions of the theory of General Relativity. Publisher: Universidade Federal de Roraima Tipo: Dissertação Fri, 05 Feb 2010 00:00:00 GMT http://localhost:8080/handle/prefix/29 2010-02-05T00:00:00Z http://localhost:8080/handle/prefix/28 Title: Gravitação newtoniana modificada a partir da teoria gravitacional de Brans-Dicke Autor(es): Paulo, Walter de Oliveira Primeiro Orientador: Barros, Adriano Trindade Abstract: We investigate initially the problem of obtaining a modified newtonian gravitation in the case of General Relativity theory. Following, we find a general solution with spherical symmetry for a weak gravitational field in the context of Brans-Dicke theory. This solution is independent of any coordinate condition. Then, for a convenient choice of the function f(r) in Brans-Dicke metric, we exhibit a modified formula to newtonian gravity, which can describe gravity in a small length scale. We discuss the results in comparison with the case of General Relativity. Publisher: Universidade Federal de Roraima Tipo: Dissertação Sat, 29 Oct 2011 00:00:00 GMT http://localhost:8080/handle/prefix/28 2011-10-29T00:00:00Z http://localhost:8080/handle/prefix/26 Title: Propriedades ópticas de poços quânticos quadrados duplos de AIGaAs em função da temperatura Autor(es): Moraes, Sérgio Sampaio de Primeiro Orientador: Sergio, Cássio Sanguini Abstract: With the growth and improvement of techniques for growth of semiconductor heterostructures has enabled the manufacture of new devices mainly on nanotechnology. In this work we present the results of our investigations and characterization through photoluminescence spectroscopy technique in three (03) samples of consisti Square Double Quantum Wells to be designated by DQW s of AlGaAs/AlAs different percentage of aluminum in the wells quantum. The samples were grown on GaAs substrate by Molecular Beam Technique Epitaxe from English MBE (Molecular Beam Epitaxy). The material of the central barrier consists of the same material as side barriers. The experimental data excitonic transition energy, obtained by analyzing the peak photoluminescence (PL) and the behavior as a function of temperature in the range of 6 K to 300 K with excitation power of 100 mW using the proposed model Varshni . The results obtained through the energy spectra of the wells show that the emission properties of heterostructures are strongly dependent on the procedure used during the deposition of the layers, especially during the exchange between the sources of the elements that make up the material. The effects of confinement and varying the concentration of Al that was present in Quantum Wells were analyzed. Publisher: Universidade Federal de Roraima Tipo: Dissertação Fri, 24 Oct 2014 00:00:00 GMT http://localhost:8080/handle/prefix/26 2014-10-24T00:00:00Z