scholarly journals Magnetized cosmological model with variable deceleration parameter

2020 ◽  
Vol 29 (13) ◽  
pp. 2050091
Author(s):  
Sankarsan Tarai ◽  
Fakhereh Md. Esmaeili ◽  
B. Mishra ◽  
S. K. Tripathy
Keyword(s):  
Magnetic Field ◽  
Cosmological Model ◽  
Deceleration Parameter ◽  
Geometrical Parameters ◽  
Late Time ◽  
Time Varying ◽  
Field Equations ◽  
Cosmic Evolution ◽  
Text Model ◽  
Algebraic Approaches

In this paper, we have derived the field equations in an extended theory of gravity in an anisotropic spacetime background and in the presence of magnetic field. The physical and geometrical parameters of the models are determined with respect to the Hubble parameter using some algebraic approaches. A time varying scale factor has been introduced to analyze the behavior of the model. From some diagnostic approach, we found that the model behaves as [Formula: see text] model at late time of cosmic evolution.

Cosmological model with variable deceleration parameter in f(R,T) modified gravity

2018 ◽  
Vol 15 (07) ◽  
pp. 1850115 ◽  
Author(s):  
Rishi Kumar Tiwari ◽  
Aroonkumar Beesham ◽  
Bhupendra Shukla
Keyword(s):  
Cosmological Model ◽  
Modified Gravity ◽  
Deceleration Parameter ◽  
Late Time ◽  
Type I ◽  
Field Equations ◽  
Geometrical Properties ◽  
Deceleration Phase ◽  
Modified Gravity Theory ◽  
The Universe

A study is made of the LRS Bianchi type-I cosmological model in [Formula: see text] modified gravity theory. Einstein’s field equations in [Formula: see text] gravity are solved by taking [Formula: see text] and the deceleration parameter [Formula: see text] to be a linear function of the Hubble parameter [Formula: see text]. The universe begins with an initial singular state and changes with time from an early deceleration phase to a late time acceleration phase. We have found that the jerk parameter [Formula: see text] in the model approaches that of the [Formula: see text] model at late times. We also discuss the physical and geometrical properties of the model.

scholarly journals An accelerating cosmological model from a parametrization of Hubble parameter

2019 ◽  
Vol 35 (05) ◽  
pp. 2050011 ◽  
Author(s):  
S. K. J. Pacif ◽  
Md Salahuddin Khan ◽  
L. K. Paikroy ◽  
Shalini Singh
Keyword(s):  
Dark Energy ◽  
Cosmological Model ◽  
Hubble Parameter ◽  
Cosmological Parameters ◽  
Cosmic Time ◽  
Solution Procedure ◽  
Cosmic Acceleration ◽  
Model Parameters ◽  
Late Time ◽  
Field Equations

In view of late-time cosmic acceleration, a dark energy cosmological model is revisited wherein Einstein’s cosmological constant is considered as a candidate of dark energy. Exact solution of Einstein field equations (EFEs) is derived in a homogeneous isotropic background in classical general relativity. The solution procedure is adopted in a model-independent way (or the cosmological parametrization). A simple parametrization of the Hubble parameter (H) as a function of cosmic time t is considered which yields an exponential type of evolution of the scale factor (a) and also shows a negative value of deceleration parameter at the present time with a signature flip from early deceleration to late acceleration. Cosmological dynamics of the model obtained have been discussed illustratively for different phases of the evolution of the universe. The evolution of different cosmological parameters is shown graphically for flat and closed cases of Friedmann–Lemaitre–Robertson–Walker (FLRW) spacetime for the presented model (open case is incompatible to the present scenario). We have also constrained our model parameters with the updated (36 points) observational Hubble dataset.

Kaluza–Klein Cosmological Model, Strange Quark Matter, and Time-Varying Lambda

2014 ◽  
Vol 69 (1-2) ◽  
pp. 90-96 ◽  
Author(s):  
Namrata Jain ◽  
Shyamsunder S. Bhoga ◽  
Gowardhan S. Khadekar
Keyword(s):  
Cosmological Model ◽  
Quark Matter ◽  
Strange Quark ◽  
Strange Quark Matter ◽  
Time Varying ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Different Types ◽  
Free Parameters ◽  
Kaluza Klein

In this paper, exact solutions of the Einstein field equations of the Kaluza-Klein cosmological model have been obtained in the presence of strange quark matter. We have considered the timevarying cosmological constant Λ as Λ = αH2 + βR-2, where α and β are free parameters. The solutions are obtained with the help of the equation of state for strange quark matter as per the Bag model, i.e. quark pressure p = 1/3(ρ - 4BC), where BC is Bag’s constant. We also discussed the physical implications of the solutions obtained for the model for different types of universes.

Phase transition of LRS Bianchi type-I cosmological model in f(R,T) gravity

2020 ◽  
Vol 17 (12) ◽  
pp. 2050187
Author(s):  
R. K. Tiwari ◽  
D. Sofuoğlu ◽  
V. K. Dubey
Keyword(s):  
Cosmological Model ◽  
Bianchi Type ◽  
Early Time ◽  
Momentum Tensor ◽  
Late Time ◽  
Type I ◽  
Field Equations ◽  
Bianchi Type I ◽  
Accelerating Expansion ◽  
Acceleration Of The Universe

In this work, LRS Bianchi type-I cosmological model with perfect fluid source in [Formula: see text] gravity theory, where [Formula: see text] is the Ricci scalar and [Formula: see text] is the trace of the stress energy-momentum tensor, has been studied in order to investigate early time deceleration and late time acceleration of the universe. By proposing a new special form of time-varying deceleration parameter in terms of Hubble parameter, the exact solution of the field equations has been obtained. The physical and geometric quantities of the model have been derived and their evolution has been discussed. Our model has an initial singularity and initially exhibits decelerating expansion and transits to accelerating expansion phase at last eras. The nature of the matter source of the model is consistent with the standard model in frame of the structure formation.

scholarly journals Lyra’s cosmology of homogeneous and isotropic universe in Brans–Dicke theory

2020 ◽  
pp. 2150029
Author(s):  
Rajendra Prasad ◽  
Lalit Kumar Gupta ◽  
Anil Kumar Yadav
Keyword(s):  
Cosmological Model ◽  
Deceleration Parameter ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Density Parameter ◽  
Field Equations ◽  
Present Universe ◽  
Age Of The Universe ◽  
Geometrical Term ◽  
The Universe ◽  
Matter Energy

In this paper, we investigate a scalar field Brans–Dicke cosmological model in Lyra’s geometry which is based on the modifications in a geometrical term as well as energy term of Einstein’s field equations. We have examined the validity of the proposed cosmological model on the observational scale by performing statistical analysis from the latest [Formula: see text] and SN Ia observational data. We find that the estimated values of Hubble’s constant and matter energy density parameter is in agreement with their corresponding values, obtained from recent observations of Wilkinson Microwave Anisotropy Probe (WMAP) and Plank collaboration. We also derived the deceleration parameter, age of the universe and jerk parameter in terms of red-shift and computed its present values. The dynamics of the deceleration parameter in the derived model of the universe show a signature flipping from positive to a negative value and also indicate that the present universe is in the accelerating phase.

Tilted Kantowski–Sachs cosmological model in Brans–Dicke theory of gravitation

2018 ◽  
Vol 33 (04) ◽  
pp. 1850011 ◽  
Author(s):  
D. D. Pawar ◽  
S. P. Shahare ◽  
V. J. Dagwal
Keyword(s):  
General Solution ◽  
Cosmological Model ◽  
Perfect Fluid ◽  
Power Law ◽  
Tensor Field ◽  
Geometrical Parameters ◽  
Field Equations ◽  
Theory Of Gravitation

Tilted Kantowski–Sachs cosmological model in Brans–Dicke theory for perfect fluid has been investigated. The general solution of field equations in Brans–Dicke theory for the combined scalar and tensor field are obtained by using power law relation. Also, some physical and geometrical parameters are obtained and discussed.

scholarly journals Bulk Viscous Cosmological Model in Brans-Dicke Theory with New Form of Time Varying Deceleration Parameter

2017 ◽  
Vol 2017 ◽  
pp. 1-24
Author(s):  
G. P. Singh ◽  
Binaya K. Bishi
Keyword(s):  
Equation Of State ◽  
Cosmological Model ◽  
Bulk Viscosity ◽  
Deceleration Parameter ◽  
Chaplygin Gas ◽  
Time Varying ◽  
Modified Chaplygin Gas ◽  
Bulk Viscous ◽  
New Form ◽  
Frw Cosmological Model

We have presented FRW cosmological model in the framework of Brans-Dicke theory. This paper deals with a new proposed form of deceleration parameter and cosmological constant Λ. The effect of bulk viscosity is also studied in the presence of modified Chaplygin gas equation of state (p=Aρ-B/ρn). Furthermore, we have discussed the physical behaviours of the models.

Holographic Dark Energy Model With Time Varying Deceleration Parameter

2018 ◽  
Vol 6 (2) ◽  
pp. 25
Author(s):  
R P. Wankhade
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Deceleration Parameter ◽  
Holographic Dark Energy ◽  
Anisotropy Parameter ◽  
Type I ◽  
Time Varying ◽  
Field Equations ◽  
Large Expansion ◽  
The Universe

Two minimally interacting fluids; dark matter and holographic dark energy components has been studied in a spatially homogeneous and anisotropic Bianchi type-I space-time. The solutions of the Einstein’s field equations are obtained under the assumption of time varying deceleration parameter (Abdussattar and S. Prajapati, Astrophys. Space Sci. 331, 65, 2011) which represents transition of the universe from the early decelerating phase to the recent accelerating phase. It is shown that for large expansion the model reduces to model while for suitable choice of interaction between dark matter and holographic dark energy the anisotropy parameter of the universe approaches to zero for large cosmic time and the coincidence parameter increases with increase in time. Allowing for time dependent deceleration parameter the solutions of the field equations and some physical and geometric properties of the model along with physical acceptability of the solutions have also been discussed in details. 

Can Noether symmetry in modified f(G) gravity always yield cosmic evolution?

2017 ◽  
Vol 32 (11) ◽  
pp. 1750046
Author(s):  
Malay Krishna Dutta ◽  
B. Modak
Keyword(s):  
Ideal Fluid ◽  
Functional Form ◽  
Noether Symmetry ◽  
Late Time ◽  
Field Equations ◽  
Symmetry Approach ◽  
Cosmic Evolution ◽  
Accelerating Expansion ◽  
Modified Theory Of Gravity ◽  
Modified Theory

We discuss Noether symmetry approach in the modified theory of gravity with Gauss–Bonnet (GB) interaction-f(G) including an ideal fluid in Friedmann–Lemaître–Robertson–Walker (FLRW) background. It yields functional form of f(G) from the symmetry. The existence of Noether symmetry gives the scale factor in two cases, but these are not satisfied by field equations in general. In another case, the solution of field equations shows late-time transition to an accelerating expansion when matter is dust, however the solution including dust and radiation is always in accelerating era.

scholarly journals Cosmological model with time varying deceleration parameter in F(R, G) gravity

2021 ◽  
Author(s):  
Santosh V. Lohakare ◽  
S K Tripathy ◽  
B Mishra
Keyword(s):  
Scalar Field ◽  
Cosmological Model ◽  
Deceleration Parameter ◽  
Dynamical Behaviour ◽  
Ricci Scalar ◽  
Energy Conditions ◽  
Time Varying ◽  
Diagnostic Stability ◽  
Field Formalism ◽  
The Universe

Abstract In this paper, we study the dynamical behaviour of the universe in the F (R, G) theory of gravity, where R and G respectively denote the Ricci scalar and Gauss-Bonnet invariant. Our wide analysis encompasses the energy conditions, cosmographic parameters, Om(z) diagnostic, stability and the viability of reconstructing the referred model through a scalar field formalism. The model obtained here shows the quintessence like behaviour at late times.

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