Bianchi type-V solutions with varying G and Λ: The general case

2020 ◽  
Vol 17 (06) ◽  
pp. 2050076
Author(s):  
Alnadhief H. A. Alfedeel ◽  
Amare Abebe
Keyword(s):  
Bianchi Type ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Energy Models ◽  
Runge Kutta Method ◽  
Gravitational And Cosmological Constants ◽  
Phantom Dark Energy ◽  
Type V ◽  
Cosmological Constants ◽  
Bianchi Type V

The homogeneous and anisotropic Bianchi type-V cosmological model with variable gravitational and cosmological “constants” with a general (nonstiff) perfect fluid is investigated. The Einstein field equations (EFEs) are numerically integrated with the fourth-order Runge–Kutta method for different values of [Formula: see text] and [Formula: see text] parameters of quantum fields in a curved and expanding background. Three realistic models, namely matter, radiation and phantom dark energy models are also discussed. In all these models, it was found that the cosmological “constant” decreases with time, whereas the gravitational “constant” increases over time. It is shown that the universe in these models becomes isotropic at late times.

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

Universe ◽  
2018 ◽  
Vol 4 (8) ◽  
pp. 83 ◽  
Author(s):  
Alnadhief Alfedeel ◽  
Amare Abebe ◽  
Hussam Gubara
Keyword(s):  
General Solution ◽  
Hypergeometric Function ◽  
Bianchi Type ◽  
Generalized Solution ◽  
Time Dependent ◽  
Field Equations ◽  
Gravitational And Cosmological Constants ◽  
Type V ◽  
Cosmological Constants ◽  
Bianchi Type V

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.

SOME BIANCHI TYPE COSMOLOGICAL MODELS IN LYRA GEOMETRY

2008 ◽  
Vol 23 (30) ◽  
pp. 4925-4931 ◽  
Author(s):  
J. K. SINGH
Keyword(s):  
Bianchi Type ◽  
Lyra Geometry ◽  
Energy Conditions ◽  
Geometrical Parameters ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Massive Scalar Field ◽  
Normal Gauge ◽  
Type V ◽  
Bianchi Type V

A class of nonstatic solutions for Einstein field equations has been investigated in the context of Bianchi type-V space–time in the theory based on Lyra's geometry in Gauss normal gauge and in the presence of an attractive massive scalar field. The results have been studied through various physical and geometrical parameters. The energy conditions of the model have also been verified.

SOME COSMOLOGICAL MODELS IN SCALAR–TENSOR THEORIES

2010 ◽  
Vol 25 (27) ◽  
pp. 2363-2371 ◽  
Author(s):  
J. K. SINGH
Keyword(s):  
Magnetic Field ◽  
Bianchi Type ◽  
Cosmological Models ◽  
Energy Conditions ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Static Solutions ◽  
Type V ◽  
The Magnetic Field ◽  
Bianchi Type V

A class of non-static solutions to the Einstein field equations has been investigated in the context of Bianchi type-V spacetime in a family of scalar–tensor theories in the presence as well as absence of the magnetic field. The physical and kinematical behaviors of the models have been discussed. The energy conditions of the models have also been verified.

BIANCHI TYPE V COSMOLOGICAL MODELS WITH PERFECT FLUID AND HEAT CONDUCTION IN LYRA'S GEOMETRY

2008 ◽  
Vol 23 (31) ◽  
pp. 4991-5005 ◽  
Author(s):  
SHRI RAM ◽  
MOHD. ZEYAUDDIN ◽  
C. P. SINGH
Keyword(s):  
Perfect Fluid ◽  
Bianchi Type ◽  
Displacement Vector ◽  
Hubble’S Parameter ◽  
Field Equations ◽  
Constant Deceleration Parameter ◽  
Displacement Vector Field ◽  
Lyra’S Geometry ◽  
Type V ◽  
Bianchi Type V

The field equations within the framework of Lyra's geometry with a time-dependent displacement vector field for a Bianchi type-V space–time filled with a perfect fluid and heat flow are presented. Two different classes of physically viable solutions are obtained by using a special law of variation for the generalized mean Hubble's parameter which correspond to singular and nonsingular models with constant deceleration parameter. These models are found to be consistent with the observations on the present day universe. Some thermodynamical relations are studied. The physical and kinematical behaviors of the models are also discussed.

scholarly journals ACCELERATING DARK ENERGY MODELS IN BIANCHI TYPE-V SPACETIME

2011 ◽  
Vol 26 (30) ◽  
pp. 2261-2275 ◽  
Author(s):  
ANIRUDH PRADHAN ◽  
HASSAN AMIRHASHCHI
Keyword(s):  
Dark Energy ◽  
Bianchi Type ◽  
Late Time ◽  
Field Equations ◽  
Future Evolution ◽  
New Exact Solutions ◽  
Spatially Homogeneous ◽  
Type V ◽  
The Universe ◽  
Bianchi Type V

Some new exact solutions of Einstein's field equations in a spatially homogeneous and anisotropic Bianchi type-V spacetime with minimally interaction of perfect fluid and dark energy components have been obtained. To prevail the deterministic solution we choose the scale factor [Formula: see text], which yields a time-dependent deceleration parameter (DP), representing a model which generates a transition of the universe from the early decelerating phase to the recent accelerating phase. We find that for n ≥ 1, the quintessence model is reproducible with present and expected future evolution of the universe. The other models (for n < 1), we observe the phantom scenario. The quintessence as well as phantom models approach to isotropy at late time. For different values of n, we can generate a class of physically viable DE models. The cosmic jerk parameter in our descended model is also found to be in good concordance with the recent data of astrophysical observations under appropriate condition. The physical and geometric properties of spatially homogeneous and anisotropic cosmological models are discussed.

scholarly journals Bianchi type-V cosmology with magnetized anisotropic dark energy

2017 ◽  
Vol 95 (3) ◽  
pp. 274-282
Author(s):  
M. Farasat Shamir ◽  
Asad Ali
Keyword(s):  
Magnetic Field ◽  
Dark Energy ◽  
Bianchi Type ◽  
Anisotropic Fluid ◽  
Physical Parameters ◽  
Anisotropic Universe ◽  
Field Equations ◽  
Constant Deceleration Parameter ◽  
Type V ◽  
Bianchi Type V

We study anisotropic universe in the presence of magnetized dark energy. Bianchi type-V cosmological model is considered for this purpose. The energy–momentum tensor consists of anisotropic fluid with uniform magnetic field of energy density ρB. Exact solutions to the field equations are obtained without using conventional assumptions like constant deceleration parameter. In particular, a general solution is obtained that further provides different classes of solutions. Only three cases have been discussed for the present analysis: linear, quadratic, and exponential. Graphical analyses of the solutions are done for all the three classes. The behavior of the model using some important physical parameters is discussed in the presence of magnetic field.

scholarly journals Viability of Bianchi type V universe in f(R,T) = f1(R) + f2(R)f3(T) gravity

2020 ◽  
Vol 17 (07) ◽  
pp. 2050111
Author(s):  
Lokesh Kumar Sharma ◽  
Benoy Kumar Singh ◽  
Anil Kumar Yadav
Keyword(s):  
Bianchi Type ◽  
Hubble Constant ◽  
Lagrangian Model ◽  
Energy Conditions ◽  
Physical Parameters ◽  
Field Equations ◽  
Eos Parameter ◽  
Bianchi Type V Universe ◽  
Type V ◽  
Bianchi Type V

In this paper, we examine the viability of Bianchi type V universe in [Formula: see text] theory of gravitation. To solve the field equations, we have considered the power law for scale factor and constructed a singular Lagrangian model which is based on the coupling between Ricci scalar [Formula: see text] and trace of energy–momentum tensor [Formula: see text]. We find the constraints on Hubble constant [Formula: see text] and free parameter [Formula: see text] with 46 observational Hubble dataset and obtain pretty satisfactory results. The physical features of the model and transitional behavior of equation of state (EOS) parameter are analyzed. We examine the nature of physical parameters and validity of energy conditions as well as stability condition. We also present the Om[Formula: see text] and statefinder diagnostic analysis for the derived model.

Exact vacuum solutions to modified Einstein field equations in f(R) gravity

2020 ◽  
Vol 35 (25) ◽  
pp. 2050205
Author(s):  
Usamah S. Al-Ali ◽  
Ashfaque H. Bokhari
Keyword(s):  
Bianchi Type ◽  
Constant Scalar Curvature ◽  
Vacuum Field ◽  
Initial Singularity ◽  
De Sitter ◽  
Field Equations ◽  
Plane Symmetric ◽  
Expansion Of The Universe ◽  
Type V ◽  
Bianchi Type V

Considering the plane symmetric non-static spacetimes in the context of [Formula: see text] gravity, we obtain exact solutions of the vacuum field equations by assuming constant scalar curvature. By suitable transformations, it is shown that the obtained solutions can be transformed to Bianchi type [Formula: see text], a type of Taub’s and the De Sitter solutions. Of particular interest is a solution that represents a model that has initial singularity and under an appropriate transformation can be converted to a Bianchi-type V model. This solution, like the Bianchi type V model, leads to predictions about evolution in the sense of an expanding universe starting from an initial singularity. In this context, we show that the expansion of the universe in [Formula: see text] gravity can be explained without invoking the cosmological constant [Formula: see text].

Domain walls and quark matter in Bianchi type-V universe with observational constraints in F(R,T) gravity

2019 ◽  
Vol 17 (01) ◽  
pp. 2050014 ◽  
Author(s):  
Dinesh Chandra Maurya ◽  
Anirudh Pradhan ◽  
Archana Dixit
Keyword(s):  
Quark Matter ◽  
Domain Walls ◽  
Bianchi Type ◽  
Momentum Tensor ◽  
Accelerated Expansion ◽  
Observational Constraints ◽  
Field Equations ◽  
Bianchi Type V Universe ◽  
Type V ◽  
Bianchi Type V

In this study, we investigate the Bianchi type-V cosmological models with quark matter (QM) distribution and domain walls with observational constraints in [Formula: see text] theory of gravity (Harko et al. in Phys. Rev. D 84 (2011) 024020), for a specific choice of the function [Formula: see text] (where [Formula: see text] is Ricci scalar and [Formula: see text] is the trace of the energy–momentum tensor). We have used model-independent methods and hyperbolic expansion scale factors to achieve the deterministic solution of the modified Einstein field equations and these are also tested observationally. The behaviors of QM and domain walls give an idea of accelerated expansion of the Universe which agrees with recent observations of Type Ia Supernovae. We also discuss the physical implications of the derived models.

Sign in / Sign up

Export Citation Format

Share Document