Cosmological Models with Variable Cosmological and Gravitational “Constants” and Bulk Viscous Models

Arbab, Arbab I.

doi:10.1023/a:1010252130608

Cited by 136 publications

(44 citation statements)

References 25 publications

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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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Section: Introductionmentioning

confidence: 99%

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

2018

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“…Lau [7], Lau and Prokhovnik [8] proposed generalized field equations with time-dependent G and Λ , since then many authors have investigated cosmological models with variables G and Λ . Arbab [9] has discussed a viscous model G and Λ , and bulk viscosity for a flat Robertson-Walker universe in the framework of general relativity.…”

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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“…The role of viscosity in cosmology has been studied by several authors viz. Pimentel [25], Berman [26], Beesham [27], Arbab [28], Pavon et al [29], Zimdahl [30], Gron [31], Saha [32,33], Singh et al [34], Bali et al [35,36], Mostafapoor and Gron [37].…”

Section: Introductionmentioning

confidence: 99%