Cosmological models with variable gravitational and cosmological ?constants?

Berman, Marcelo Samuel

doi:10.1007/bf00756609

Cited by 102 publications

(61 citation statements)

References 8 publications

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“…All parameters, ρ, p, Λ, θ, σ, H 1 , H 2 and H 3 tend to zero, and G is constant at late times. Therefore, the model essentially gives an empty universe for large t. The ratio σ/θ → 0 as t → ∞, which shows that the model approaches isotropy for large value of t. We see that Λ is positive and also Λ ∼ 1/t 2 , i.e., Λ is a decreasing function of time [25]. This supports the results obtained from recent supernova Ia observations [40].…”

Section: Zel'dovich Fluid Distribution (ω = 1)supporting

confidence: 80%

Deceleration Parameter

The Encyclopedia of Astronomy and Astrophysics

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Section: Zel'dovich Fluid Distribution (ω = 1)supporting

confidence: 80%

Deceleration Parameter

The Encyclopedia of Astronomy and Astrophysics

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“…The calculations of quantum field theory predict the value of vacuum to be of the order of 10 130 s −2 , whereas the cosmological constant value is of the order of 10 −20 s −2 ; hence, a new thought is required to explain or resolve this puzzle. The idea of considering the cosmological models as varying vacuum energy density Λ has extensively been adapted by several authors [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

A Generalized Solution of Bianchi Type-V Models with Time-Dependent G and Λ

2018

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Abstract:We study the homogeneous but anisotropic Bianchi type-V cosmological model with time-dependent gravitational and cosmological "constants". Exact solutions of the Einstein field equations (EFEs) are presented in terms of adjustable parameters of quantum field theory in a spatially curved and expanding background. It has been found that the general solution of the average scale factor a as a function of time involved the hypergeometric function. Two cosmological models are obtained from the general solution of the hypergeometric function and the Emden-Fowler equation.The analysis of the models shows that, for a particular choice of parameters in our first model, the cosmological "constant" decreases whereas the Newtonian gravitational "constant" increases with time, and for another choice of parameters, the opposite behaviour is observed. The models become isotropic at late times for all parameter choices of the first model. In the second model of the general solution, both the cosmological and gravitational "constants" decrease while the model becomes more anisotropic over time. The exact dynamical and kinematical quantities have been calculated analytically for each model.

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“…The coefficient of viscosity decreases as universe expands. The nature of viscosity in cosmology in Bianchi Type V cosmological model has been examined by number of authors 2,3,4,5 and with heat flow by Banerjee and Sanyal 6 . Ram 7 has investigated perfect fluid distribution in general relativity in…”

Section: Introductionmentioning

confidence: 99%

Stiff Fluid Distribution with Variable G and  Assuming Power Law Relation in Bianchi type V Viscous Cosmological Model

TINKER¹

2017

jusps-B

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We have investigated Bianchi Type V stiff fluid cosmological model with variable gravitational and cosmological constant. To get the exact solution it is assumed that equation of state is P = p -3  H, =p, where  =  0  h , p is the isotropic pressure,  is the coefficient of shear viscosity, H the Hubble constant,  0 and h are taken as constants. A, B and C are assumed as the functions of cosmic time t using power law relation. Some other physical and geometrical aspects of the model are also discussed in terms of cosmic time t.

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Cosmological models with variable gravitational and cosmological ?constants?

Cited by 102 publications

References 8 publications

Deceleration Parameter

Deceleration Parameter

A Generalized Solution of Bianchi Type-V Models with Time-Dependent G and Λ

Stiff Fluid Distribution with Variable G and  Assuming Power Law Relation in Bianchi type V Viscous Cosmological Model

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