BIANCHI TYPE-II COSMOLOGICAL MODELS WITH CONSTANT DECELERATION PARAMETER

2006 ◽  
Vol 15 (03) ◽  
pp. 419-438 ◽  
Author(s):  
C. P. SINGH ◽  
SURESH KUMAR
Keyword(s):  
Deceleration Parameter ◽  
Bianchi Type ◽  
Physical Models ◽  
Type Ii ◽  
Anisotropic Space ◽  
Hubble’S Parameter ◽  
Field Equations ◽  
Constant Deceleration Parameter ◽  
Exponential Expansion ◽  
Rotationally Symmetric

A special law of variation for Hubble's parameter in anisotropic space–time models that yields a constant value of the deceleration parameter is presented. Also, a spatially homogeneous and anisotropic but locally rotationally symmetric (LRS) Bianchi type-II cosmological model is studied with a perfect fluid and constant deceleration parameter. Assuming the equation of state p = γρ, where 0≤γ≤1, and using a special law of variation for the Hubble parameter, we are able to construct many new solutions to Einstein's field equations of LRS Bianchi type-II for four different physical models (dust, radiation, Zel'dovich and vacuum). We discuss the solutions with power-law and exponential expansion and examine a particular class of models. A detailed study of kinematic, geometrical and observational properties is carried out.

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 LRS Bianchi type-I cosmological model with constant deceleration parameter in f(R,T) gravity

2017 ◽  
Vol 14 (11) ◽  
pp. 1750158 ◽  
Author(s):  
Binaya K. Bishi ◽  
S. K. J. Pacif ◽  
P. K. Sahoo ◽  
G. P. Singh
Keyword(s):  
Cosmological Model ◽  
Deceleration Parameter ◽  
Hubble Parameter ◽  
Bianchi Type ◽  
Specific Model ◽  
Type I ◽  
Hubble’S Parameter ◽  
Constant Deceleration Parameter ◽  
Bianchi Type I ◽  
Spatially Homogeneous

A spatially homogeneous anisotropic LRS Bianchi type-I cosmological model is studied in [Formula: see text] gravity with a special form of Hubble's parameter, which leads to constant deceleration parameter. The parameters involved in the considered form of Hubble parameter can be tuned to match, our models with the [Formula: see text]CDM model. With the present observed value of the deceleration parameter, we have discussed physical and kinematical properties of a specific model. Moreover, we have discussed the cosmological distances for our model.

Dark energy models in LRS Bianchi type-II space-time in the new perspective of time-dependent deceleration parameter

2017 ◽  
Vol 14 (05) ◽  
pp. 1750077 ◽  
Author(s):  
Dinesh Chandra Maurya ◽  
Rashid Zia ◽  
Anirudh Pradhan
Keyword(s):  
Dark Energy ◽  
Deceleration Parameter ◽  
Bianchi Type ◽  
Time Dependent ◽  
Type Ii ◽  
Field Equations ◽  
Type Ia ◽  
New Perspective ◽  
Ia Supernovae ◽  
The Universe

Before 1998, it was usually expected that the universe was expanding with a constant rate or the expansion was slowing down. In 1998, the surprising discovery based on type Ia supernovae, that the rate of expansion of the universe is increasing, forced the researchers to reconsider the various cosmological models proposed so far. The current study is also an effort to revisit the LRS Bianchi type-II, dark energy (DE) model by taking time-dependent deceleration parameter (DP) instead of constant DP. We have assumed the variable scale factor [Formula: see text], which gives the variable DP as [Formula: see text], with these considerations, the solutions of field equations are calculated. Various parameters of DE models are also calculated, and it is found that these are consistent with the recent observations.

Study of cosmic models in f(R,T) gravity with tilted observers

2020 ◽  
Vol 35 (38) ◽  
pp. 2050316
Author(s):  
V. J. Dagwal ◽  
D. D. Pawar ◽  
Y. S. Solanke
Keyword(s):  
Bianchi Type ◽  
Physical Models ◽  
Energy Tensor ◽  
Type I ◽  
Field Equations ◽  
Constant Deceleration Parameter ◽  
Stress Energy ◽  
State Formula ◽  
Radiation Universe ◽  
Graphical Presentation

In this work, we have studied LRS Bianchi type I cosmological models in [Formula: see text] gravity with tilted observers, where [Formula: see text] is the Ricci scalar and [Formula: see text] is the trace of the stress energy tensor. We have explored a tilted model and determined the solutions of the field equations by assuming special law of variation of Hubble’s parameter, proposed by Berman (1983) that yields constant deceleration parameter. In this scenario, we have used the equation of state [Formula: see text] and power law of velocity to describe the different anisotropic physical models such as Dust Universe, Radiation Universe, Hard Universe and Zedovich Universe. We have discussed graphical presentation of all parameters of the derived models with the help of MATLAB. Some physical and geometrical aspects of the models are also discussed.

Anisotropic Bianchi type-II modified holographic Ricci dark energy model in scale-covariant theory of gravitation

2021 ◽  
Author(s):  
Shri Ram ◽  
S. Chandel ◽  
M.K. Verma
Keyword(s):  
Dark Energy ◽  
Bianchi Type ◽  
Covariant Theory ◽  
Type Ii ◽  
Field Equations ◽  
Ricci Dark Energy ◽  
Scale Covariant Theory ◽  
Cosmological Observations ◽  
Negative Constant ◽  
Theory Of Gravitation

In this paper, we obtain an anisotropic Bianchi type-II space-time with dark matter and the modified holographic Ricci dark energy in the scale-covariant theory of gravitation. Exact solutions of the field equations are obtained by assuming (I) a negative constant value of the deceleration parameter (II) the component σ<sup>1</sup><sub>1</sub> of the shear tensor σ<sup>j</sup><sub>i</sub> is proportional to the mean Hubble parameter and (III) the gauge function Φ is proportional to a power function of the average scale factor. We have also discussed some important physical aspects of the model which is in agreement with the modern cosmological observations.

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