Brans-Dicke static universes

Berman, Marcelo Samuel; Som, M. M.; Gomide, Fernando de Mello

doi:10.1007/bf00764101

Cited by 81 publications

(46 citation statements)

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“…An important role of cosmological constant with the relation 2 t − Λ ∝ studied by Berman et al [2] and Berman [3] [4]. The time variation of the gravitational constant G was first proposed by Dirac [5] and extensively discussed in the literature by Weinberg [6].…”

Section: Introductionmentioning

confidence: 99%

Bianchi Type-V Cosmological Models for Perfect Fluid with Time-Varying Gravitational and Cosmological Constant

Ullah¹,

Hossain²,

Alam³

2017

JAMP

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Einstein's field equations with variable gravitational and cosmological constants are considered in presence of perfect fluid for locally-rotationallysymmetric (LRS) Bianchi type-V space-time discussion in context of the particle creation. We present new shear free solutions for both absence and presence of particle creation. The solution describes the particle and entropy generation in the anisotropic cosmological models. We observe that time variation of gravitational and cosmological constant is needed for particle creation phenomena. Moreover, we obtained the particle production rate ( ) t Γ for this model and discussed in detail.

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Section: Introductionmentioning

confidence: 99%

Bianchi Type-V Cosmological Models for Perfect Fluid with Time-Varying Gravitational and Cosmological Constant

Ullah¹,

Hossain²,

Alam³

2017

JAMP

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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 work of Singh and Rai [7] give a detailed survey of Brans-Dicke cosmological models discussed by several authors. Nariai [8], Reddy and Rao [9], Banerjee and Santos [10], Singh et al [11], Ram [12], Ram and Singh [13], Berman et al [14], Reddy et al [15] are some of the authors who have investigated several aspects of this theory. Reddy and Venkateswara Rao [16] and Reddy et al [17] discussed Bianchi type I cosmological models with negative constant declaration parameter in scalar tensor theories formulated by Brans-Dicke theory and Saez-Ballester theory [18].…”

Section: Introductionmentioning

confidence: 99%