scholarly journals Anisotropic Cosmological Models with Two Fluids

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
B. Mishra ◽  
Pratik P. Ray ◽  
S. K. J. Pacif
Keyword(s):  
Dark Energy ◽  
Power Law ◽  
Momentum Tensor ◽  
Cosmological Models ◽  
De Sitter ◽  
Eos Parameter ◽  
Two Fluids ◽  
Anisotropic Dark Energy ◽  
Bulk Viscous Fluid ◽  
De Sitter Universe

Anisotropic dark energy cosmological models have been constructed in a Bianchi V space-time, with the energy momentum tensor consisting of two noninteracting fluids, namely, bulk viscous fluid and dark energy fluid. Two different models are constructed based on the power law cosmology and de Sitter universe. The constructed model was also embedded with different pressure gradients along different spatial directions. The variable equation of state (EoS) parameter and skewness parameters for both models are obtained and analysed. The physical properties of the models obtained with the use of scale factors of power law and de Sitter law are also presented.

scholarly journals Magnetized Anisotropic Dark Energy Models in Barber’s Second Self-Creation Theory

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
D. D. Pawar ◽  
Y. S. Solanke
Keyword(s):  
Magnetic Field ◽  
Dark Energy ◽  
Momentum Tensor ◽  
Anisotropic Fluid ◽  
Eos Parameter ◽  
Conservation Of Energy ◽  
Anisotropic Dark Energy ◽  
Energy Models ◽  
The Mean ◽  
Energy Components

The present paper deals with Bianchi type IX cosmological model with magnetized anisotropic dark energy by using Barber’s self-creation theory. The energy momentum tensor consists of anisotropic fluid with EoS parameterωand a uniform magnetic field of energy densityρB. In order to obtain the exact solution we have assumed that dark energy components and the components of magnetic field interact minimally and obey the law of conservation of energy momentum tensors. We have also used the special law of variation for the mean generalized Hubble parameter and power law relation between scalar field and scale factor. Some physical and kinematical properties of the models have been discussed.

Kantowski-Sachs cosmological models with anisotropic dark energy

Open Physics ◽  
2011 ◽  
Vol 9 (4) ◽  
Author(s):  
Kishor Adhav ◽  
Abhijit Bansod ◽  
Rajesh Wankhade ◽  
Hanumant Ajmire
Keyword(s):  
Dark Energy ◽  
Exact Solutions ◽  
Power Law ◽  
Cosmological Models ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Anisotropic Dark Energy

AbstractThe exact solutions of the Einstein field equations for dark energy in Kantowski-Sachs metric under the assumption on the anisotropy of the fluid are obtained for exponential and power-law volumetric expansions. The isotropy of the fluid, space and expansion are examined.

Bianchi type-VI0 cosmological models with anisotropic dark energy

2010 ◽  
Vol 332 (2) ◽  
pp. 497-502 ◽  
Author(s):  
K. S. Adhav ◽  
A. S. Bansod ◽  
S. L. Munde ◽  
R. G. Nakwal
Keyword(s):  
Dark Energy ◽  
Bianchi Type ◽  
Cosmological Models ◽  
Anisotropic Dark Energy ◽  
Bianchi Type Vi0

scholarly journals Physical Acceptability of the Renyi, Tsallis and Sharma-Mittal Holographic Dark Energy Models in the f(T,B) Gravity under Hubble’s Cutoff

Universe ◽  
2021 ◽  
Vol 7 (3) ◽  
pp. 67
Author(s):  
Salim Harun Shekh ◽  
Pedro H. R. S. Moraes ◽  
Pradyumn Kumar Sahoo
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
Field Equations ◽  
Eos Parameter ◽  
Two Fluids ◽  
Gravitational Field Equations ◽  
Energy Models ◽  
Different Types ◽  
The Universe

In the present article, we investigate the physical acceptability of the spatially homogeneous and isotropic Friedmann–Lemâitre–Robertson–Walker line element filled with two fluids, with the first being pressureless matter and the second being different types of holographic dark energy. This geometric and material content is considered within the gravitational field equations of the f(T,B) (where T is the torsion scalar and the B is the boundary term) gravity in Hubble’s cut-off. The cosmological parameters, such as the Equation of State (EoS) parameter, during the cosmic evolution, are calculated. The models are stable throughout the universe expansion. The region in which the model is presented is dependent on the real parameter δ of holographic dark energies. For all δ≥4.5, the models vary from ΛCDM era to the quintessence era.

String inspired cosmological models through Lagrangian invariance

2020 ◽  
Vol 17 (06) ◽  
pp. 2050085
Author(s):  
José Antonio Belinchón ◽  
Danae Polychroni
Keyword(s):  
Perfect Fluid ◽  
Power Law ◽  
Matter Field ◽  
Scale Factor ◽  
Cosmological Models ◽  
De Sitter ◽  
Text Field ◽  
Duality Property ◽  
Constant Potential ◽  
Variable Potential

We study a string inspired cosmological with variable potential through the Lagrangian invariance method in order to determine the form of the potential. We have studied four cases by combining the different fields, that is, the dilaton [Formula: see text] the potential [Formula: see text] the [Formula: see text]-field and the matter field (a perfect fluid). In all the studied cases, we found that the potential can only take two possible forms: [Formula: see text] and [Formula: see text] where [Formula: see text] and [Formula: see text] are numerical constants. We conclude that when we take into account the Kalb–Ramond field, i.e. the [Formula: see text]-field, then it is only possible to get a constant potential, [Formula: see text] Nevertheless, if this field is not considered, then we get two possible solutions for the potential: [Formula: see text] and [Formula: see text] In all the cases, if the potential is constant, [Formula: see text] then we get a de Sitter like solution for the scale factor of the metric, [Formula: see text], which verifies the [Formula: see text]-duality property, while if the potential varies, then we get a power-law solution for the scale factor, [Formula: see text] [Formula: see text]

Dynamical system approach for the modified Brans–Dicke theory

2019 ◽  
Vol 28 (10) ◽  
pp. 1950132 ◽  
Author(s):  
Jianbo Lu ◽  
Xin Zhao ◽  
Shining Yang ◽  
Jiachun Li ◽  
Molin Liu
Keyword(s):  
Dynamical System ◽  
Dark Energy ◽  
Critical Point ◽  
System Approach ◽  
State Parameter ◽  
Kinetic Term ◽  
De Sitter ◽  
Dynamical System Approach ◽  
De Sitter Universe ◽  
Manifold Theory

A modified Brans–Dicke theory (abbreviated as GBD) is proposed by generalizing the Ricci scalar [Formula: see text] to an arbitrary function [Formula: see text] in the original BD action. It can be found that the GBD theory has some interesting properties, such as solving the problem of PPN value without introducing the so-called chameleon mechanism (comparing with the [Formula: see text] modified gravity), making the state parameter to crossover the phantom boundary: [Formula: see text] without introducing the negative kinetic term (comparing with the quintom model). In the GBD theory, the gravitational field equation and the cosmological evolutional equations have been derived. In the framework of cosmology, we apply the dynamical system approach to investigate the stability of the GBD model. A five-variable cosmological dynamical system and three critical points ([Formula: see text], [Formula: see text], [Formula: see text]) are obtained in the GBD model. After calculation, it is shown that the critical point [Formula: see text] corresponds to the radiation dominated universe and it is unstable. The critical point [Formula: see text] is unstable, which corresponds to the geometrical dark energy dominated universe. While for case of [Formula: see text], according to the center manifold theory, this critical point is stable, and it corresponds to geometrical dark energy dominated de Sitter universe ([Formula: see text]).

scholarly journals Rip cosmologies, wormhole solutions and big trip in the f(T,𝒯 ) theory of gravity

2020 ◽  
Vol 17 (08) ◽  
pp. 2050116 ◽  
Author(s):  
Maxime Z. Arouko ◽  
Ines G. Salako ◽  
A. D. Kanfon ◽  
M. J. S. Houndjo ◽  
Etienne Baffou
Keyword(s):  
Energy Momentum Tensor ◽  
Late Phase ◽  
Momentum Tensor ◽  
Cosmological Models ◽  
The Other ◽  
Throat Radius ◽  
Eos Parameter ◽  
Wormhole Throat ◽  
Initial Epoch ◽  
Theory Of Gravity

Rip cosmological models have been investigated in the framework of [Formula: see text] theory of gravity, where [Formula: see text] denotes the torsion and [Formula: see text] is the trace of the energy–momentum tensor. These phantom cosmological models revealed that at initial epoch a EoS parameter [Formula: see text] tends asymptotically at late phase to [Formula: see text] [Formula: see text]. On the other hand, Wormhole Solutions and Big Trip have been subject to an investigation. The wormhole throat radius [Formula: see text] and the conditions to be satisfied to produce the Big Trip phenomenon have been discussed.

scholarly journals LITTLE RIP COSMOLOGICAL MODELS WITH TIME-DEPENDENT EQUATION OF STATE

2012 ◽  
Vol 27 (36) ◽  
pp. 1250210 ◽  
Author(s):  
I. BREVIK ◽  
V. V. OBUKHOV ◽  
K. E. OSETRIN ◽  
A. V. TIMOSHKIN
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Cosmological Models ◽  
Time Dependent ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Energy Models ◽  
Sitter Spacetime ◽  
The Universe ◽  
Far Future

Specific dark energy models, leading to the Little Rip (LR) cosmology in the far future, are investigated. Conditions for the occurrence of LR in terms of the parameters present in the proposed equation of state for the dark energy cosmic fluid are studied. Estimates about the time needed before the occurrence of the small singularity in the standard LR model in which the universe approaches the de Sitter spacetime asymptotically, are given.

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