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By adopting the co-moving coordinate system, an exact axially symmetric cosmological model with string dust cloud source is obtained in the framework of Brans-Dicke [Phys. Rev. 124, 925, (1961) Scalar – tensor theory of gravitation. Some physical and kinematical properties of the model are also discussed. 相似文献
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Marcelo Samuel Berman 《Astrophysics and Space Science》2007,312(3-4):275-278
We discuss astronomical and astrophysical evidence, which we relate to the principle of zero-total energy of the Universe,
that imply several relations among the mass M, the radius R and the angular momentum L of a “large” sphere representing a Machian Universe. By calculating the angular speed, we find a peculiar centripetal acceleration
for the Universe. This is an ubiquituous property that relates one observer to any observable. It turns out that this is exactly
the anomalous acceleration observed on the Pioneers spaceships. We have thus shown that this anomaly is to be considered a
property of the Machian Universe. We discuss several possible arguments against our proposal. 相似文献
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A Bianchi type-I string cosmological model in Brans-Dicke theory in five dimension space-time has been investigated. For the
determinate solution it has been assumed that the sum of energy density and tension density of the cosmic string dust source
vanishes. Some physical and kinematical parameters are also discussed. 相似文献
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Marcelo Samuel Berman 《Astrophysics and Space Science》2008,314(1-3):79-82
A combined BCDE (Brans-Dicke and Einstein-Cartan) theory with lambda-term is developed through Raychaudhuri’s equation, for
inflationary scenario. It involves a variable cosmological constant, which decreases with time, jointly with energy density,
cosmic pressure, shear, vorticity, and Hubble’s parameter, while the scale factor, total spin and scalar field increase exponentially.
The post-inflationary fluid resembles a perfect one, though total spin grows, but the angular speed does not (Astrophys. Space
Sci. 312: 275, 2007d).
相似文献
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Sudipto Roy 《天文和天体物理学研究(英文版)》2019,(4):137-150
A cosmological model has been constructed in the framework of Brans-Dicke(BD) gravity,based on an inter-conversion between matter and dark energy, for a spatially flat universe in the era of pressureless dust. To account for the non-conservation of the matter content, a function of time f(t) has been arbitrarily put into the expression for the density of matter(ρa^3= f(t)ρ_0 a_0~3). By definition, f(t) is proportional to the matter content of the universe. Using suitable ansatzes for the scale factor and scalar field, the functional form of f(t) has been determined from the BD field equations. The scale factor has been so chosen that it would cause a signature flip in the deceleration parameter with time. The function f(t) decreases monotonically with time, indicating a transformation of matter into dark energy. The time dependence of the proportions of matter and dark energy in the universe has been determined. The effect of non-conservation of the matter content upon various cosmological parameters has been explored in the present study. Two models of matter-energy interaction have been proposed and f(t) has been expressed as a function of their interaction term. The dark energy equation-of-state(EoS) parameter has been expressed and analyzed in terms of f(t). 相似文献
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T. R. Seshadri 《Journal of Astrophysics and Astronomy》1997,18(4):339-342
The historical motivation for the Brans-Dicke theory and its connection with Mach’s principle has been discussed. Some examples
of actions which can be reduced to the Brans-Dicke type have been given. Further, the recent developments in the theory in
the context of inflationary cosmology have been briefly pointed out. 相似文献
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