scholarly journals BIG RIP AND OTHER SINGULARITIES IN ISOTROPIC HOMOGENEOUS COSMOLOGICAL MODELS WITH ARBITRARY EQUATION OF STATE

2015 ◽  
Vol 28 (2) ◽  
pp. 137-140 ◽  
Author(s):  
S. L. Parnovsky
Keyword(s):  
Equation Of State ◽  
Cosmological Models ◽  
Big Rip ◽  
Homogeneous Cosmological Models

Hypersurface-homogeneous cosmological models with dynamical equation of state parameter in Lyra geometry

2015 ◽  
Vol 93 (10) ◽  
pp. 1100-1105 ◽  
Author(s):  
Shri Ram ◽  
S. Chandel ◽  
M.K. Verma
Keyword(s):  
Dynamical Equation ◽  
State Parameter ◽  
Lyra Geometry ◽  
Cosmological Models ◽  
Anisotropic Fluid ◽  
Late Time ◽  
Field Equations ◽  
Homogeneous Cosmological Models ◽  
Negative Constant ◽  
Equation Of State Parameter

The hypersurface homogeneous cosmological models are investigated in the presence of an anisotropic fluid in the framework of Lyra geometry. Exact solutions of field equations are obtained by applying a special law of variation for mean Hubble parameter that gives a negative constant value of the deceleration parameter. These solutions correspond to anisotropic accelerated expanding cosmological models that isotropize for late time even in the presence of anisotropic fluid. The anisotropy of the fluid also isotropizes at late time. Some physical and kinematical properties of the model are also discussed.

Cosmological models in R2 gravity with hybrid expansion law

2021 ◽  
pp. 2150143
Author(s):  
Partha Sarathi Debnath ◽  
Bikash Chandra Paul
Keyword(s):  
Equation Of State ◽  
Deceleration Parameter ◽  
State Parameter ◽  
Cosmological Models ◽  
Model Parameters ◽  
Density Parameter ◽  
Eos Parameter ◽  
Data Set ◽  
Deceleration Phase ◽  
Higher Derivative

In this paper, evolution of a Friedmann–Robertson–Walker universe is studied in a higher derivative theory of gravity. The relativistic solutions admitting hybrid expansion law of the universe are explored here. Hybrid expansion law is a general form of scale factor from which one can recover both the power-law expansion and exponential expansion as a special case. The hybrid expansion law is interesting as it addresses the early deceleration phase and presents accelerating phase satisfactorily. It is found that an inflationary scenario with hybrid expansion law is permitted in the [Formula: see text] gravity fairly well. We consider universe filled with cosmic fluid that describes by an equation of state (EoS) parameter which varies with time. Consequently, we analyze the time variation of energy density parameter, cosmic pressure, equation of state parameter, deceleration parameter and jerk parameter in the cosmological model. The constraints of the model parameters imposed by the cosmological observational data set are determined. The present value of the deceleration parameter [Formula: see text], EoS parameter and the epoch at which the transition of decelerated phase to accelerated phase are estimated. In the higher derivative theory, we obtain some new and interesting cosmological solutions relevant for building cosmological models.

scholarly journals ATTRACTOR SOLUTION IN COUPLED YANG–MILLS FIELD DARK ENERGY MODELS

2009 ◽  
Vol 18 (09) ◽  
pp. 1331-1342 ◽  
Author(s):  
WEN ZHAO
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
De Sitter ◽  
Yang Mills ◽  
Constraint Equations ◽  
Energy Models ◽  
Big Rip ◽  
Attractor Solution ◽  
The Universe ◽  
Mills Field

We investigate the attractor solution in the coupled Yang–Mills field dark energy models with the general interaction term, and obtain the constraint equations for the interaction if the attractor solution exists. The research also shows that, if the attractor solution exists, the equation of state of dark energy must evolve from wy > 0 to wy ≤ -1, which is slightly suggested by the observation. At the same time, the total equation of state in the attractor solution is w tot = -1, the universe is a de Sitter expansion, and the cosmic big rip is naturally avoided. These features are all independent of the interacting forms.

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.

RECONSTRUCTION OF 5D COSMOLOGICAL MODELS FROM THE EQUATION OF STATE OF DARK ENERGY

2006 ◽  
Vol 15 (02) ◽  
pp. 215-224 ◽  
Author(s):  
LI XIN XU ◽  
HONG YA LIU ◽  
CHENG WU ZHANG
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Arbitrary Function ◽  
Equations Of State ◽  
Cosmological Models ◽  
Cosmological Solutions ◽  
The Universe

We consider a class of five-dimensional cosmological solutions which contain two arbitrary function μ(t) and ν(t). We find that the arbitrary function μ(t) contained in the solutions can be rewritten in terms of the redshift z as a new arbitrary function f(z). We further show that this new arbitrary function f(z) can be solved for four known parameterized equations of state of dark energy. Then 5D models can be reconstructed and the evolution of the density and deceleration parameters of the universe can be determined.

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