Cosmological constant Λ in f(R,T) modified gravity

2016 ◽  
Vol 13 (05) ◽  
pp. 1650058 ◽  
Author(s):  
Gyan Prakash Singh ◽  
Binaya Kumar Bishi ◽  
Pradyumn Kumar Sahoo
Keyword(s):  
Cosmological Model ◽  
Cosmological Constant ◽  
Modified Gravity ◽  
Bianchi Type ◽  
Field Equations ◽  
Type Iii ◽  
Expansion Scalar ◽  
Modified Theory Of Gravity ◽  
Shear Scalar ◽  
Modified Theory

In this paper, we have studied the Bianchi type-III cosmological model in the presence of cosmological constant in the context of [Formula: see text] modified theory of gravity. Here, we have discussed two classes of [Formula: see text] gravity, i.e. [Formula: see text] and [Formula: see text]. In both classes, the modified field equations are solved by the relation expansion scalar [Formula: see text] that is proportional to shear scalar [Formula: see text] which gives [Formula: see text], where [Formula: see text] and [Formula: see text] are metric potentials. Also we have discussed some physical and kinematical properties of the models.

Bianchi type-II universe with linear equation of state

Open Physics ◽  
2014 ◽  
Vol 12 (8) ◽  
Author(s):  
Kishor Adhav ◽  
Ishwar Pawade ◽  
Abhijit Bansod
Keyword(s):  
General Relativity ◽  
Equation Of State ◽  
Cosmological Model ◽  
Linear Equation ◽  
Bianchi Type ◽  
Type Ii ◽  
Field Equations ◽  
Expansion Scalar ◽  
Shear Scalar

AbstractWe have studied anisotropic and homogeneous Bianchi type-II cosmological model with linear equation of state (EoS) p = αρ−β, where α and β are constants, in General Relativity. In order to obtain the solutions of the field equations we have assumed the geometrical restriction that expansion scalar θ is proportional to shear scalar σ. The geometrical and physical aspects of the model are also studied.

scholarly journals Bianchi type-VI0 modified holographic Ricci dark energy model in a scalar–tensor theory

2017 ◽  
Vol 95 (2) ◽  
pp. 179-183 ◽  
Author(s):  
M. Vijaya Santhi ◽  
V.U.M. Rao ◽  
Y. Aditya
Keyword(s):  
Dark Energy ◽  
Bianchi Type ◽  
Scalar Tensor Theory ◽  
Field Equations ◽  
Ricci Dark Energy ◽  
Tensor Theory ◽  
Expansion Scalar ◽  
Shear Scalar ◽  
Average Scale Factor ◽  
Good Agreement

In this paper, we consider Bianchi type-VI0 space–time filled with anisotropic modified holographic Ricci dark energy in a scalar–tensor theory proposed by Brans–Dicke (Phys. Rev. 124, 925 (1961)). The field equations in this scalar–tensor theory, have been solved for the following physically relevant assumptions: (i) the scalar field ([Formula: see text]) is proportional to average scale factor (a(t)), (ii) expansion scalar (θ) in the model is proportional to shear scalar (σ). It has been observed that the presented universe is in an accelerating phase at the present epoch, which is in good agreement with the recent astronomical observations. We have also discussed some other properties of the obtained model.

scholarly journals Bianchi Type-I Universe with Cosmological Constant and Quadratic Equation of State inf(R,T)Modified Gravity

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
G. P. Singh ◽  
Binaya K. Bishi
Keyword(s):  
Equation Of State ◽  
Cosmological Constant ◽  
Modified Gravity ◽  
Bianchi Type ◽  
Quadratic Equation ◽  
Type I ◽  
Field Equations ◽  
Bianchi Type I ◽  
Bianchi Type I Universe ◽  
Quadratic Equation Of State

This paper deals with the study of Bianchi type-I universe in the context off(R,T)gravity. Einstein’s field equations inf(R,T)gravity have been solved in the presence of cosmological constantΛand quadratic equation of state (EoS)p=αρ2-ρ, whereα≠0is a constant. Here, we have discussed two classes off(R,T)gravity; that is,f(R,T)=R+2f(T)andf(R,T)=f1(R)+f2(T). A set of models has been taken into consideration based on the plausible relation. Also, we have studied some physical and kinematical properties of the models.

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 LRS Bianchi Type-I Inflationary String Cosmological Model in Brans-Dicke Theory of Gravitation

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
R. Venkateswarlu ◽  
J. Satish
Keyword(s):  
Scalar Field ◽  
Cosmological Model ◽  
Power Law ◽  
Bianchi Type ◽  
Type I ◽  
Physical Behavior ◽  
Bianchi Type I ◽  
Expansion Scalar ◽  
Theory Of Gravitation ◽  
Shear Scalar

We investigate locally rotational symmetric (LRS) Bianchi type I space time coupled with scalar field. String cosmological models generated by a cloud of strings with particles attached to them are studied in the Brans-Dicke theory. We assume that the expansion scalar is proportional to the shear scalar and also power law ansatz for scalar field. The physical behavior of the resulting model is discussed through different parameters.

scholarly journals Anisotropic Bianchi Type-III Bulk Viscous Fluid Universe in Lyra Geometry

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
Priyanka Kumari ◽  
M. K. Singh ◽  
Shri Ram
Keyword(s):  
Cosmological Model ◽  
Viscous Fluid ◽  
Bianchi Type ◽  
Lyra Geometry ◽  
Scale Factor ◽  
Field Equations ◽  
Type Iii ◽  
Bulk Viscous Fluid ◽  
Bulk Viscous ◽  
The Universe

An anisotropic Bianchi type-III cosmological model is investigated in the presence of a bulk viscous fluid within the framework of Lyra geometry with time-dependent displacement vector. It is shown that the field equations are solvable for any arbitrary function of a scale factor. To get the deterministic model of the universe, we have assumed that (i) a simple power-law form of a scale factor and (ii) the bulk viscosity coefficient are proportional to the energy density of the matter. The exact solutions of the Einstein’s field equations are obtained which represent an expanding, shearing, and decelerating model of the universe. Some physical and kinematical behaviors of the cosmological model are briefly discussed.

scholarly journals Bianchi type-III cosmological model with quadratic EoS in Lyra geometry

2018 ◽  
Vol 15 (11) ◽  
pp. 1850194 ◽  
Author(s):  
Mahbubur Rahman Mollah ◽  
Kangujam Priyokumar Singh ◽  
Pheiroijam Suranjoy Singh
Keyword(s):  
Equation Of State ◽  
Cosmological Model ◽  
Exact Solutions ◽  
Bianchi Type ◽  
Lyra Geometry ◽  
Quadratic Equation ◽  
Anisotropic Space ◽  
Field Equations ◽  
Type Iii ◽  
Quadratic Equation Of State

The paper deals with the investigation of a homogeneous and anisotropic space-time described by Bianchi type-III metric with perfect fluid in Lyra geometry setting. Exact solutions of Einstein’s field equations have been obtained under the assumption of quadratic equation of state (EoS) of the form [Formula: see text], where [Formula: see text] is a constant and strictly [Formula: see text]. The physical and geometrical aspects are also examined in detail.

Sign in / Sign up

Export Citation Format

Share Document