Bulk Viscous Bianchi Type-V Cosmological Models with Variable Gravitational and Cosmological Constant

Singh, G. P.; Kale, A. Y.

doi:10.1007/s10773-009-0116-9

Cited by 14 publications

(9 citation statements)

References 54 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: 73%

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: 73%

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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“…Following Luis (1985), Johari and Kalyani (1994), Singh and Beesham (1999) and recently Singh and Kale (2009), we assume the well accepted power law relation between gravitational constant G and scale factor a as…”

Section: Solutions Of the Field Equationsmentioning

confidence: 99%

“…Following, Singh and Kale (2009), the relation between τ and coefficient of bulk viscosity ξ is given by…”

Section: Bulk Viscosity In Eckart's Theory the Evolution Equation (39mentioning

confidence: 99%

“…Therefore the best currently available theory for analyzing dissipative processes in the Universe is the Full Isreal-Stewart theory (FIS). Several authors (Kremer and Devecchi 2003;Singh and Beesham 2000;Debnath et al 2007;Singh and Kale 2009) and recently Yadav (2010Yadav ( , 2011 have obtained cosmological models with dissipative effects. ; Singh (2009); Singh and Kumar (2009) and Bali and Kumawat (2008) have studied matter filled imperfect fluid in different physical context.…”

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confidence: 99%

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Bulk viscous LRS Bianchi-I Universe with variable G and decaying Λ

Yadav

Pradhan

Singh

2011

Astrophys Space Sci

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The present study deals with spatially homogeneous and totally anisotropic locally rotationally symmetric (LRS) Bianchi type I cosmological model with variable G and in presence of imperfect fluid. To get the deterministic model of Universe, we assume that the expansion (θ ) in the model is proportional to shear (σ ). This condition leads to A = B n , where A, B are metric potential. The cosmological constant is found to be decreasing function of time and it approaches a small positive value at late time which is supported by recent Supernovae Ia (SN Ia) observations. Also it is evident that the distance modulus curve of derived model matches with observations perfectly.

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“…Singh and Kumar [34] have discussed viscous fluid cosmology in Bianchi type-I space-time with thermodynamical properties in general relativity. Singh and Kale [35] have investigated bulk viscous Bianchi type V cosmological models with variable gravitational and cosmological constant. Bali and Chandnani [36] have studied Bianchi type-V barotropic perfect fluid cosmological model in Lyra geometry.…”

mentioning

confidence: 99%

Bianchi Type-III Bulk Viscous and Barotropic Perfect Fluid Cosmological Models in Lyra’s Geometry

Yadav

2011

Int J Theor Phys

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We have investigated Bianchi type III bulk viscous and barotropic perfect fluid cosmological models in the frame work of Lyra's geometry. To get deterministic models of universe, we have assumed the three conditions: (i) shear scalar (σ ) is proportional to the expansion (θ ). This leads to B = C n , where B and C are metric potentials. (ii) In presence of viscous fluid, the coefficient of viscosity of dissipative fluid is a power function of mass density ξ = ξ 0 ρ m , where ξ 0 and m are constant and (iii) in absence of viscosity, a proportionality relation between pressure and energy density of barotropic perfect fluid p = αρ, where α is a proportionality constant. In all the cases, we observed that the displacement vector β is large at beginning of the universe and reduces fast during its evolution so that its nature coincide with the behavior of cosmological constant .

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Bulk Viscous Bianchi Type-V Cosmological Models with Variable Gravitational and Cosmological Constant

Cited by 14 publications

References 54 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

Bulk viscous LRS Bianchi-I Universe with variable G and decaying Λ

Bianchi Type-III Bulk Viscous and Barotropic Perfect Fluid Cosmological Models in Lyra’s Geometry

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