scholarly journals Mixed fluid cosmological model in f(R, T) gravity

2020 ◽  
Vol 98 (11) ◽  
pp. 1015-1022 ◽  
Author(s):  
Parbati Sahoo ◽  
Barkha Taori ◽  
K.L. Mahanta
Keyword(s):  
Cosmological Model ◽  
Bianchi Type ◽  
Type I ◽  
Time Varying ◽  
Eos Parameter ◽  
Barotropic Fluid ◽  
Rotationally Symmetric ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Mixed Fluid

We construct a locally rotationally symmetric (LRS) Bianchi type-I cosmological model in f(R, T) theory of gravity when the source of gravitation is a mixture of barotropic fluid and dark energy (DE) by employing a time-varying deceleration parameter. We observe through the behavior of the state finder parameters (r, s) that our model begins from the Einstein static era and goes to ΛCDM era. The equation of state (EOS) parameter (ωd) for DE varies from the phantom (ω < –1) phase to quintessence (ω > –1) phase, which is consistent with observational results. It is found that the discussed model can reproduce the current accelerating phase of the expansion of the universe.

The Mimetic Matter in LRS Bianchi Type-I Model

2021 ◽  
Author(s):  
Ertan Gudekli ◽  
E. Demir
Keyword(s):  
Bianchi Type ◽  
State Parameter ◽  
Relativity Theory ◽  
Type I ◽  
Field Equations ◽  
Bianchi Type I ◽  
Rotationally Symmetric ◽  
Bianchi Type I Universe ◽  
Expansion Of The Universe ◽  
The Universe

This paper deals with the Locally rotationally symmetric (LRS) Bianchi type-I universe model in Mimetic Gravity Theory assuming it an extended form of General Relativity Theory. It was proclaimed as a conformal transformation of the Einstein-Hilbert action from Einstein frame to Jordon frame. At the outset, we have proposed a potential function on account of clarifying the expansion of our universe by considering the general solutions of the field equations that originate from the action of the theory including the Lagrange multipliers. Lastly, after having been achieved the general equation of the state parameter ω, we discussed whether the result corresponds to some fluids illuminating the expansion of the Universe or not.

scholarly journals LOCALLY ROTATIONALLY SYMMETRIC BIANCHI TYPE-I COSMOLOGICAL MODEL IN f(T) GRAVITY: FROM EARLY TO DARK ENERGY DOMINATED UNIVERSE

2014 ◽  
Vol 23 (01) ◽  
pp. 1450004 ◽  
Author(s):  
M. E. RODRIGUES ◽  
I. G. SALAKO ◽  
M. J. S. HOUNDJO ◽  
J. TOSSA
Keyword(s):  
Dark Energy ◽  
Cosmological Model ◽  
Dark Energy Model ◽  
Bianchi Type ◽  
Rotational Symmetry ◽  
Type I ◽  
Bianchi Type I ◽  
Reconstruction Scheme ◽  
Rotationally Symmetric ◽  
The Universe

We study the locally rotational symmetry Bianchi type-I dark energy model in the framework of f(T) theory of gravity, where T denotes the torsion scalar. A viable cosmological model is undertaken and the isotropization of this latter is checked, yielding a result that reflects the real evolution of our universe. Moreover, still in the anisotropic optic, a more complicated f(T) model is obtained from the cosmological reconstruction scheme and the analysis shows that the universe is more anisotropic at the beginning if the terms of higher order in T are not considered. This means that the nonlinear model should be favored by observational data.

scholarly journals Bianchi type–I Model with Time Varying Λ and G: The Generalized Solution

2020 ◽  
Vol 29 (1) ◽  
pp. 89-93
Author(s):  
Alnadhief H. A. Alfedeel
Keyword(s):  
Analytical Solution ◽  
Bianchi Type ◽  
Generalized Solution ◽  
Type I ◽  
Time Varying ◽  
Field Equations ◽  
Geometric Function ◽  
Varying Λ ◽  
The Universe ◽  
Average Scale Factor

AbstractIn this paper, we have investigated the homogeneous and anisotropic Bianchi type–I cosmological model with a time-varying Newtonian and cosmological constant. We have analytically solved Einstein’s field equations (EFEs) in the presence of a stiff-perfect fluid. We show that the analytical solution for the average scale factor for the generalized Friedman equation involves the hyper-geometric function. We have studied the physical and kinematical quantities of the model, and it is found that the universe becomes isotropic at late times.

scholarly journals Locally Rotationally Symmetric Bianchi Type-I Cosmological Model in f(R,T) Gravity

2019 ◽  
Vol 1344 ◽  
pp. 012004
Author(s):  
M.Vijaya Santhi ◽  
Daba Meshesha Gusu ◽  
V.U.M. Rao ◽  
G. Suryanarayana
Keyword(s):  
Cosmological Model ◽  
Bianchi Type ◽  
Type I ◽  
Bianchi Type I ◽  
Locally Rotationally Symmetric ◽  
Rotationally Symmetric

BULK VISCOUS BIANCHI TYPE I BAROTROPIC FLUID COSMOLOGICAL MODEL WITH VARYING Λ AND FUNCTIONAL RELATION ON HUBBLE PARAMETER IN ROSEN’S BIMETRIC GRAVITY

2021 ◽  
Vol 10 (5) ◽  
pp. 2515-2525
Author(s):  
N.P. Gaikwad ◽  
P.V. Lepse ◽  
B.K. Bishi ◽  
N.K. Ashtankar
Keyword(s):  
Cosmological Model ◽  
Hubble Parameter ◽  
Bianchi Type ◽  
Functional Relation ◽  
Late Time ◽  
Type I ◽  
Bianchi Type I ◽  
Barotropic Fluid ◽  
Bimetric Gravity ◽  
Bulk Viscous

We have deduced that bulk viscous Bianchi type I barotropic fluid cosmological model with varying $\Lambda$ and functional relation on hubble parameter by solving the field equations bimetric theory of gravitation. It is observed that our model has exponentially accelerating expansion at late time starting with decelerating expansion which agreed the observation of Perlmutter (1998), Knop (2003), Tegmark (2004) and Spergel (2006). In the beginning, our model has more than three spatial-dimensions then it switched over to three-dimensional spatial geometry at late epoch of time and it is agreed with Borkar et al. (2013). Other geometrical and physical behavior of the model have been studied.

scholarly journals Anisotropic Cosmological Model in a Modified Theory of Gravitation

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 226
Author(s):  
Rishi Kumar Tiwari ◽  
Aroonkumar Beesham ◽  
Soma Mishra ◽  
Vipin Dubey
Keyword(s):  
Cosmological Model ◽  
Modified Gravity ◽  
Bianchi Type ◽  
Late Time ◽  
Type I ◽  
Bianchi Models ◽  
Theory Of Gravitation ◽  
The Universe ◽  
Type Parameter ◽  
Modified Theory

Current observations indicate that, on a large enough scale, the universe is homogeneous and isotropic. However, this does not preclude the possibility of some anisotropy having occurred during the early stages of the evolution of the universe, which could then have been damped out later. This idea has aroused interest in the Bianchi models, which are homogeneous but anisotropic. Secondly, there is much interest in modified gravity these days due to the problems that the usual ΛCDM model faces in general relativity. Hence, in this paper, a study was conducted on the Bianchi type-I cosmological model in f(R,T)-modified gravity. Following some ideas from cosmography, a specific form of the deceleration parameter was assumed, leading to a model that exhibited a transition from early deceleration to late-time acceleration. The derived model approached isotropy at late times. The physical properties of the model were discussed, and expressions for the various parameters of the model were derived. It is also possible to make progress towards solving the cosmological constant problem, since in this model in f(R,T) gravity, a variable cosmological-type parameter arose, which was large early on but decreased to a constant value in later times.

scholarly journals Bianchi type-I string cosmological model in the presence of a magnetic flux: exact and qualitative solutions

Open Physics ◽  
2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Bijan Saha ◽  
Victor Rikhvitsky ◽  
Mihai Visinescu
Keyword(s):  
Magnetic Flux ◽  
Cosmological Model ◽  
Qualitative Analysis ◽  
Analytical Solutions ◽  
Present Model ◽  
Bianchi Type ◽  
Einstein Equations ◽  
Type I ◽  
Bianchi Type I ◽  
The Universe

AbstractA Bianchi type-I cosmological model in the presence of a magnetic flux along a cosmological string is investigated. The objective of this study is to generate solutions to the Einstein equations using a few tractable assumptions usually accepted in the literature. The analytical solutions are supplemented with numerical and qualitative analysis. In the frame of the present model the evolution of the Universe and other physical aspects are discussed.

AN LRS BIANCHI TYPE-I COSMOLOGICAL MODEL WITH TIME-DEPENDENT Λ TERM

2007 ◽  
Vol 16 (04) ◽  
pp. 745-754 ◽  
Author(s):  
J. P. SINGH ◽  
R. K. TIWARI
Keyword(s):  
Cosmological Model ◽  
Bianchi Type ◽  
Large Fraction ◽  
Cosmological Term ◽  
Type I ◽  
De Sitter ◽  
Stiff Matter ◽  
Bianchi Type I ◽  
Rotationally Symmetric ◽  
De Sitter Universe

In this paper, we investigate locally rotationally symmetric (LRS) Bianchi type-I cosmological model containing stiff matter with a cosmological term proportional to the Hubble parameter. This variation law for vacuum density has recently been proposed by Schützhold on the basis of quantum field estimations in the curved and expanding background. The model obtained approaches isotropy. The cosmological term tends asymptotically to a genuine cosmological constant and the model tends to a de Sitter universe. We obtain that the present universe is accelerating with a large fraction of cosmological density in the form of cosmological term. Taking matter density equal to half of the vacuum density, as suggested by observation, we obtain a universe age given by Ht = 0.55 and a decelerating parameter equal to 2σ2/3H2.

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