Cosmological Solutions
Mostrando 1-12 de 12 artigos, teses e dissertações.
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1. Ondas gravitacionais e o espectro de anisotropia tensorial na presença de neutrinos cosmológicos
In this work we have studied the evolution of primordial gravitational waves coupled to anisotropic stress tensor of cosmological neutrinos. As in a radiation dominated universe, in a universe dominated by radiation and matter the neutrinos can work as an effective dispersive medium for the gravitational waves, besides introduce small modifications over the
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 10/07/2012
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2. Aspectos clássicos da cosmologia inflacionária.
The last decades have been of major developments in cosmology since the advent of cosmological inflation as a solution to the problems of standard cosmological model. As one of the main paradigms of modern cosmology, to study the classical theory of inflation is the main objective of this work. Before, we present the main evidences of universal expansion and
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 08/08/2011
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3. Sobre algumas soluções das equações de Einstein com constante cosmológica
In this work, through appropriate coordinate transformations and using Einsteins equations of the general relativity, we show a method to get, from the Minkowski metric, the metric of Friedmann-Lemaıtre-Robertson-Walker, used in cosmology, with the energy-momentum tensor of a perfect isotropic fluid. We obtain also an apparently new solution to Einstein
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 23/03/2010
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4. Buracos negros em universos brana com constante cosmológica / Black holes in brane worlds with cosmological constant
We found classes of static and spherically symmetric black hole solutions on the brane for a vacuum configuration, non-null cosmological constant, embedded into a 5-dimensional asymptotically anti-de Sitter bulk. In the asymptotically de Sitter case, the only solution obtained was the extreme Schwarzschild-de Sitter geometry. In the asymptotically anti-de Si
Publicado em: 2008
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5. Cosmological models of universe with variable deceleration parameter in Lyra's manifold
FRW models of the universe have been studied in the cosmological theory based on Lyra's manifold. A new class of exact solutions has been obtained by considering a time dependent displacement field for variable deceleration parameter from which three models of the universe are derived (i) exponential (ii) polynomial and (iii) sinusoidal form respectively. Th
Brazilian Journal of Physics. Publicado em: 2006-12
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6. Criação da matéria em cosmologias com velocidade da luz variável e eletrônico não-linear
In this work we obtain the cosmological solutions and investigate the thermodynamics of matter creation in two diferent contexts. In the first we propose a cosmological model with a time varying speed of light c. We consider two diferent time dependence of c for a at Friedmann-Robertson- Walker (FRW) universe. We write the energy conservation law arising fro
Publicado em: 2006
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7. Exact solutions of Brans-Dicke cosmology and the cosmic coincidence problem
We present some cosmological solutions of Brans-Dicke theory, characterized by a decaying vacuum energy density and by a constant relative matter density. With these features, they shed light on the cosmological constant problems, leading to a presently small vacuum term, and to a constant ratio between the vacuum and matter energy densities. By fixing the o
Brazilian Journal of Physics. Publicado em: 2005-12
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8. Phase space solutions in scalar-tensor cosmological models
An analysis of the solutions for the field equations of generalized scalar-tensor theories of gravitation is performed through the study of the geometry of the phase space and the stability of the solutions, with special interest in the Brans-Dicke model. Particularly, we believe to be possible to find suitable forms of the Brans-Dicke parameter w and potent
Brazilian Journal of Physics. Publicado em: 2005-12
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9. Remarks on some vacuum solutions of scalar-tensor cosmological models
We present a class of exact vacuum solutions corresponding to de Sitter and warm inflation models in the framework of scalar-tensor cosmologies. We show that in both cases the field equations reduce to planar dynamical systems with constraints. Then, we carry out a qualitative analysis of the models by examining the phase diagrams of the solutions near the e
Brazilian Journal of Physics. Publicado em: 2004-06
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10. Soluções cosmológicas e locais para uma eletrodinâmica modificada
No presente trabalho são investigadas algumas conseqüências da utilização de uma nova lagrangeana para a eletrodinâmica em dois contextos: um universo espacialmente homogêneo e isotrópico com campo magnético mais um parâmetro cosmológico A e o problema da massa puntual caregada e estática (buraco negro carregado). No caso cosmológico, foram obti
Publicado em: 2001
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11. Sobre a termodinamica dos buracos negros fortes e suas possiveis aplicações
In this work WG initially put forth an improved version of a unified approach to gravitational and strong interactions, based on the geometrical methods of General Relativity. According to it, hadrons can be regarded as "black hole type" solutions of new field equations proposed to describe two tensorial metric fields (the ordinary gravitational field and th
Publicado em: 1987
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12. Shock-wave cosmology inside a black hole
We construct a class of global exact solutions of the Einstein equations that extend the Oppeheimer–Snyder model to the case of nonzero pressure, inside the black hole, by incorporating a shock wave at the leading edge of the expansion of the galaxies, arbitrarily far beyond the Hubble length in the Friedmann–Robertson–Walker (FRW) spacetime. Here the
National Academy of Sciences.