Bianchi type-I cosmological models with variable G and Λ-term in general relativity

Singh, Jagdish P.; Pradhan, Anirudh; Singh, Ajay Kumar

doi:10.1007/s10509-008-9742-6

Cited by 40 publications

(28 citation statements)

References 58 publications

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“…The gravitational constant is found to increase with time with a varying rate. This increasing nature of , with time, has been found in many other studies [28,29,30,32,35].…”

Section: Theoretical Modelsupporting

confidence: 72%

A Study of Transition of the Expansion of the Universe from a Phase of Deceleration to Acceleration through a Conversion of Matter into Dark Energy in the Framework of Brans-Dicke Theory

2015

IJSR

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The present study is based on a generalized form of Brans-Dicke (BD) theory where, the dimensionless BD parameter is regarded as a function of the scalar field, which is reciprocal of the gravitational constant. The field equations have been solved by incorporating an empirical function f(t) in the expression representing the conservation of matter. This function f(t) has been chosen to account for a conversion of matter (both dark and baryonic) into some other form, possibly dark energy, which is known to be responsible for the accelerated expansion of universe. The requirement of a signature flip of the deceleration parameter (q), which is evident from other studies, sets the boundary conditions to be satisfied by the function f(t), leading to the formulation of its time dependence. A simple empirical relation was initially assumed to represent the time dependence of f(t), and the constants in this expression have been determined from these boundary conditions. The BD parameter has been found to have a negative value throughout the range of study. The dependence of BD parameter upon the scalar field has been depicted graphically. A smooth transition of the universe, from a decelerated to an accelerated phase of expansion, is found to occur due to a conversion of matter into dark energy. The gravitational constant is found to be increasing with time.

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“…The gravitational constant is found to increase with time with a varying rate. This increasing nature of , with time, has been found in many other studies [28,29,30,32,35].…”

Section: Theoretical Modelsupporting

confidence: 72%

A Study of Transition of the Expansion of the Universe from a Phase of Deceleration to Acceleration through a Conversion of Matter into Dark Energy in the Framework of Brans-Dicke Theory

2015

IJSR

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“…Pradhan et al [23] derived FRW universe with verying G and . Since Bianchi type I spaces are subsequent generalization of zero curvature FRW models, Singh et al [24] obtained some Bianchi type I models with variable G and . Singh et al [25] obtained early viscous universe with variable G and .…”

Section: Introductionmentioning

confidence: 99%

Bianchi-Type VI<sub>0</sub> Bulk Viscous Fluid Models with Variable Gravitational and Cosmological Constants

Verma¹,

Ram²

2011

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This paper deals with Bianchi type VI 0 anisotropic cosmological models filled with a bulk viscous cosmic fluid in the presence of time-varying gravitational and cosmological constant. Physically realistic solutions of Einstein's field equations are obtained by assuming the conditions 1) the expansion scalar is proportional to shear scalar 2) the coefficient of the bulk viscosity is a power function of the energy density and 3) the cosmic fluid obeys the barotropic equation of state. We observe that the corresponding models retain the well established features of the standard cosmology and in addition, are in accordance with recent type Ia supernovae observations. Physical behaviours of the cosmological models are also discussed.

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“…Pradhan et al (2007) have obtained FRW universes with variable G and . Singh et al (2008) have discussed Bianchi type-I cosmological models with variable G and term in general relativity. In the early stages of the universe when neutrino decoupling occurred, the matter behaved like a viscous fluid.…”

Section: Introductionmentioning

confidence: 99%

Bulk viscous fluid hypersurface–homogeneous cosmological models with time varying G and Λ

Ram

Verma

2010

Astrophys Space Sci

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Hypersurface-homogeneous cosmological models containing a bulk viscous fluid with time varying G and have been presented. We have shown that the field equations are solvable for any arbitrary cosmic scale function. The viscosity coefficient of bulk viscous fluid is assumed to be a power function of the energy density. Exact solutions of Einstein's field equations are obtained which represent an expanding, shearing and accelerating/decelerating models of the universe. The physical and kinematical behaviours of the models are also discussed.

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Bianchi type-I cosmological models with variable G and Λ-term in general relativity

Cited by 40 publications

References 58 publications

A Study of Transition of the Expansion of the Universe from a Phase of Deceleration to Acceleration through a Conversion of Matter into Dark Energy in the Framework of Brans-Dicke Theory

A Study of Transition of the Expansion of the Universe from a Phase of Deceleration to Acceleration through a Conversion of Matter into Dark Energy in the Framework of Brans-Dicke Theory

Bianchi-Type VI<sub>0</sub> Bulk Viscous Fluid Models with Variable Gravitational and Cosmological Constants

Bulk viscous fluid hypersurface–homogeneous cosmological models with time varying G and Λ

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Bianchi type-I cosmological models with variable G and Λ-term in general relativity

Cited by 40 publications

References 58 publications

A Study of Transition of the Expansion of the Universe from a Phase of Deceleration to Acceleration through a Conversion of Matter into Dark Energy in the Framework of Brans-Dicke Theory

A Study of Transition of the Expansion of the Universe from a Phase of Deceleration to Acceleration through a Conversion of Matter into Dark Energy in the Framework of Brans-Dicke Theory

Bianchi-Type VI&lt;sub&gt;0&lt;/sub&gt; Bulk Viscous Fluid Models with Variable Gravitational and Cosmological Constants

Bulk viscous fluid hypersurface–homogeneous cosmological models with time varying G and Λ

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Bianchi-Type VI<sub>0</sub> Bulk Viscous Fluid Models with Variable Gravitational and Cosmological Constants