A Theoretical Study of the Characteristics of Time Evolution of Some Cosmological Parameters (original) (raw)
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Physics Essays, 2017
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International Journal of Scientific Research in Science and Technology, 2019
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A theoretical model, regarding the time dependence of several cosmological parameters, has been constructed in the framework of generalized Brans-Dicke theory, using its field equations for spatially flat FRW metric. An empirical expression of the scalar field parameter, written in terms of the scale factor, has been substituted into the field equations to obtain expressions of Brans-Dicke dimensionless parameter (𝜔) and the density of matter (𝜌), in terms of several relevant cosmological parameters. The dark energy, which is regarded as responsible for the accelerated expansion of the universe, is assumed to have generated from matter. On the basis of a model of matter to dark energy conversion, an expression of the density of dark energy has been derived. Using these relations of matter and dark energy density, expressions regarding the proportions of matter and dark energy have been formulated. To study the time dependence of all these quantities, an empirical time dependent expression of scale factor has been incorporated into their expressions. This scale factor expression has been so chosen that, the deceleration parameter derived from it, changes sign from positive to negative, as time goes on, implying the widely accepted change of phase from deceleration to acceleration, in cosmic expansion. Time dependence of gravitational constant and various other parameters and their interdependence have been depicted graphically.
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