Bianchi VI h with variable gravitational and cosmological constants

Belinchón, José Antonio

doi:10.1007/s10509-013-1622-z

Cited by 6 publications

(3 citation statements)

References 67 publications

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“…The mathematical solutions do not allow us to know if G is growing or decreasing, both cases are allowed (they are thermodynamically consistent, with ρ decreasing, Π < 0, etc.) and they are in agreement with the observations, since some of them conclude that G is growing while another ones indicate that G is decreasing (see for instance [28] or for a short review [60]). We take into account some observational data which indicate us that Λ > 0 (see [61,62]).…”

Section: Discussionsupporting

confidence: 88%

Exact solutions of a full causal bulk viscous FRW cosmological model with variable G and Λ through factorization

Belinchón

Cornejo-Pérez

2017

Can. J. Phys.

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We study the classical flat full causal bulk viscous FRW cosmological model with variable gravitational and cosmological constants through the factorization method. The method allows us to find some new exact parametric solutions. The assumptions made bring us to study two approaches. We find, in the studied cases, that the Universe ends in an accelerating era except in the case of a particular solution where the Universe could be noninflationary for all times. In both approaches the cosmological constant is a decreasing function of time, while the gravitational constant behaves as a growing or decreasing time function depending on the sign of Λ. By taking into account recent observations that indicate that Λ must be positive, we conclude that G increases with time except in the first solution where both "constants" tend asymptotically in the large time limit to a constant value. We also present a new factorization scheme which allows us to generate new solutions to a kind of variable coefficient nonlinear second order ODE.

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Section: Discussionsupporting

confidence: 88%

Exact solutions of a full causal bulk viscous FRW cosmological model with variable G and Λ through factorization

Belinchón

Cornejo-Pérez

2017

Can. J. Phys.

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“…Canuto et al [35,36] also studied G-varying cosmologies. Cosmological models with timedependent G were also studied in some works [37][38][39]. As we know, the conservation of the energy momentum law is also an essential part of modeling the universe and it yields:…”

Section: Field Equations and Thermodynamicsmentioning

confidence: 99%

Thermodynamics of cosmological models with generalized G and Λ

Singh¹,

Singh²

2018

Turk J Phys

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Abstract:Here we investigate spatially flat Friedmann-Robertson-Walker space-time models of the universe to study the thermodynamic behaviors in light of variables G and Λ . A particular method to find the solutions of Einstein's field equations and mathematical expressions for temperature and entropy of the perfect fluid cosmological models is introduced by using both the equation of state and the assumption G = G0 a n . It is observed that the phantom field of ( ω < −1) is thermodynamically not viable when the temperature increases with the evolution of the universe. The second law of thermodynamics is also constrained by cosmological models with time-dependent G and Λ . The mathematical expressions for the look-back time, proper distance, luminosity distance, and angular diameter distances are obtained for an isotropic stiff-fluid model and their significances are investigated. The most interesting part of the investigation is that the dynamical and physical behaviors of the models are less constrained by the second law of thermodynamics.

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“…Various tests are developed to get a clear picture of cosmologies with variable G as discussed by Canuto et al [14,15,45]. Few of fundamental work in this direction of cosmological models with variable G in literature may be found in [4,5,25]. Later Hubble diagram of Type I a Supernovae also testify the dynamic gravitational constant [25].…”

Section: Introductionmentioning

confidence: 99%

Accelerating Cosmological Models With Variable G and Λ-Term in General Relativity

Bhardwaj¹,

Singh²

2022

SEAJMMS

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In this paper, we have presented a new class of accelerating universe models with variable cosmological term Λ(t) and gravitational constant G(t) in the framework of general relativity. To get exact solution of Einstein’s field equations for homogeneous and anisotropic Bianchi type-V space-time, a time varying de- celeration parameters is considered as q = 1 + nα , where n, α are constants. The present model shows a point type singularity at origin. The results establish the quintessence like behavior of model initially, and approaches to ΛCDM model ultimately. Some geometrical and physical properties of the models have been evidenced, and conferred to derive the validity of models with respect to recent astrophysical observations. Stability of the model has been discussed through the means of Om(z) diagnostic and state-finder analysis.

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Bianchi VI h with variable gravitational and cosmological constants

Cited by 6 publications

References 67 publications

Exact solutions of a full causal bulk viscous FRW cosmological model with variable G and Λ through factorization

Exact solutions of a full causal bulk viscous FRW cosmological model with variable G and Λ through factorization

Thermodynamics of cosmological models with generalized G and Λ

Accelerating Cosmological Models With Variable G and Λ-Term in General Relativity

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