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.

scholarly journals A modified holographic Ricci dark energy model in a self-creation cosmology

2016 ◽  
Vol 94 (12) ◽  
pp. 1314-1318 ◽  
Author(s):  
M.P.V.V. Bhaskara Rao ◽  
D.R.K. Reddy ◽  
K. Sobhan Babu
Keyword(s):  
Dark Energy ◽  
Dark Energy Model ◽  
Bianchi Type ◽  
Energy Model ◽  
Smooth Transition ◽  
Type Ii ◽  
Field Equations ◽  
Ricci Dark Energy ◽  
Theory Of Gravitation ◽  
The Universe

This paper deals with a locally rotationally symmetric Bianchi type II space–time with dark matter and anisotropic modified holographic Ricci dark energy as source in second self-creation theory of gravitation proposed by Barber (Gen. Relativ. Gravit. 14, 117 (1982)). To solve the field equations of this theory we have used (i) hybrid expansion law, (ii) a relation between metric potentials and a modified holographic Ricci dark energy given by Chen and Jing (Phys. Lett. B, 679, 144 (2009)). The solution obtained represents a Bianchi type II modified holographic dark energy model in self-creation cosmology. We observe that there is a smooth transition of the universe from decelerated phase to accelerated phase. This fact is in good agreement with the observations of modern cosmology. We have also discussed some important physical aspects of the model.

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.

scholarly journals RECONSTRUCTION OF 5D COSMOLOGICAL MODELS FROM RECENT OBSERVATIONS

2007 ◽  
Vol 16 (10) ◽  
pp. 1573-1579
Author(s):  
CHENGWU ZHANG ◽  
LIXIN XU ◽  
YONGLI PING ◽  
HONGYA LIU
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Equation Of State ◽  
Cosmological Solution ◽  
Type Ia Supernovae ◽  
Shift Parameter ◽  
Type Ia ◽  
Ia Supernovae ◽  
Best Fit ◽  
The Universe

We use a parameterized equation of state (EOS) of dark energy to a 5D Ricci-flat cosmological solution and suppose the universe contains two major components: dark matter and dark energy. Using the recent observational datasets: the latest 182 type Ia Supernovae Gold data, the three-year WMAP CMB shift parameter and the SDSS baryon acoustic peak, we obtain the best fit values of the EOS and two major components' evolution. We find that the best fit EOS crosses -1 in the near past where z ≃ 0.07, the present best fit value of wx(0) < -1 and for this model, the universe experiences the acceleration at about z ≃ 0.5.

scholarly journals Constraints on barotropic dark energy models by a new phenomenological q(z) parameterization

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
Jaime Román-Garza ◽  
Tomás Verdugo ◽  
Juan Magaña ◽  
Verónica Motta
Keyword(s):  
Dark Energy ◽  
Joint Analysis ◽  
Effective Equation ◽  
Phantom Divide ◽  
Plane Analysis ◽  
Energy Models ◽  
A Value ◽  
Type Ia ◽  
Ia Supernovae ◽  
The Universe

Abstract In this paper, we propose a new phenomenological two parameter parameterization of q(z) to constrain barotropic dark energy models by considering a spatially flat Universe, neglecting the radiation component, and reconstructing the effective equation of state (EoS). This two free-parameter EoS reconstruction shows a non-monotonic behavior, pointing to a more general fitting for the scalar field models, like thawing and freezing models. We constrain the q(z) free parameters using the observational data of the Hubble parameter obtained from cosmic chronometers, the joint-light-analysis Type Ia Supernovae (SNIa) sample, the Pantheon (SNIa) sample, and a joint analysis from these data. We obtain, for the joint analysis with the Pantheon (SNIa) sample a value of q(z) today, $$q_0=-0.51\begin{array}{c} +0.09 \\ -0.10 \end{array}$$q0=-0.51+0.09-0.10, and a transition redshift, $$z_t=0.65\begin{array}{c} +0.19 \\ -0.17 \end{array}$$zt=0.65+0.19-0.17 (when the Universe change from an decelerated phase to an accelerated one). The effective EoS reconstruction and the $$\omega '$$ω′–$$\omega $$ω plane analysis point towards a transition over the phantom divide, i.e. $$\omega =-1$$ω=-1, which is consistent with a non parametric EoS reconstruction reported by other authors.

scholarly journals Anisotropic magnetized holographic Ricci dark energy cosmological models

2017 ◽  
Vol 95 (4) ◽  
pp. 381-392 ◽  
Author(s):  
M. Vijaya Santhi ◽  
V.U.M. Rao ◽  
Y. Aditya
Keyword(s):  
General Relativity ◽  
Dark Energy ◽  
Deceleration Parameter ◽  
Bianchi Type ◽  
Cosmological Models ◽  
Field Equations ◽  
Ricci Dark Energy ◽  
Theor Phys ◽  
Linearly Varying Deceleration Parameter ◽  
Spatially Homogeneous

In this paper, we have considered spatially homogeneous and anisotropic Bianchi type-III space–time filled with matter and anisotropic modified holographic Ricci dark energy in general relativity. We have solved Einstein’s field equations using the following possibilities: (i) hybrid expansion law proposed by Akarsu et al. (JCAP, 01, 022 (2014)); (ii) a varying deceleration parameter considered by Mishra et al. (Int. J. Theor. Phys. 52, 2546 (2013)); and (iii) a linearly varying deceleration parameter given by Akarsu and Dereli (Int. J. Theor. Phys. 51, 612 (2012)). We have presented the cosmological models in each of the preceding cases and studied their evolutions. We have also discussed physical and kinematical properties of the models.

Transit dark energy string cosmological models with perfect fluid in F(R,T)-gravity

2018 ◽  
Vol 15 (10) ◽  
pp. 1850168 ◽  
Author(s):  
Rashid Zia ◽  
Dinesh Chandra Maurya ◽  
Anirudh Pradhan
Keyword(s):  
Dark Energy ◽  
Early Time ◽  
Momentum Tensor ◽  
Late Time ◽  
Field Equations ◽  
Accelerating Expansion ◽  
Type Ia ◽  
Dynamical Parameters ◽  
The Stability ◽  
The Universe

In this paper, spatially homogeneous and anisotropic Bianchi type-[Formula: see text] dark energy (DE) cosmological transit models with string fluid source in [Formula: see text] gravity [T. Harko et al., Phys. Rev. D 84 (2011) 024020], where [Formula: see text] is the Ricci scalar and [Formula: see text] the trace of the stress energy–momentum tensor, have been studied in the context of early time decelerating and late-time accelerating expansion of the Universe as suggested by the recent observations. The exact solutions of the field equations are obtained first by using generalized hybrid expansion law (HEL) [Formula: see text] which yields a time-dependent deceleration parameter [Formula: see text] and second by considering the metric coefficient [Formula: see text]. By using recent constraints from supernovae type-Ia union data [Cunha, arXiv:0811.2379[astro-ph]], we obtain [Formula: see text] and [Formula: see text] for transit model [Formula: see text]. The Universe has an initial singularity and is anisotropic closed and it tends to be flat at the late time, i.e. our Universe is in accelerating expansion. Our model shows a phase transition property from decelerating to accelerating. It is remarkable to mention here that our Universe is homogeneous and anisotropic in the early phase whereas it becomes homogeneous and isotropic for [Formula: see text]. We have also discussed the stability of the background solution with respect to perturbations of the metric along with the properties of future singularities in the Universe dominated by DE including the phantom-type fluid. Various physical and dynamical parameters are also calculated and investigated in terms of time and redshift both.

scholarly journals Supernovae, the Accelerating Cosmos, and Dark Energy

2012 ◽  
Vol 10 (H16) ◽  
pp. 17-17
Author(s):  
Brian Schmidt
Keyword(s):  
Dark Energy ◽  
Accelerating Universe ◽  
Type Ia Supernovae ◽  
Current State ◽  
Cosmological Application ◽  
Type Ia ◽  
Ia Supernovae ◽  
The Universe

AbstractType Ia supernovae remain one of Astronomy's most precise tools for measuring distances in the Universe. I describe the cosmological application of these stellar explosions, and chronicle how they were used to discover an accelerating Universe in 1998 - an observation which is most simply explained if more than 70% of the Universe is made up of some previously undetected form of ‘Dark Energy’. Over the intervening 13 years, a variety of experiments have been completed, and even more proposed to better constrain the source of the acceleration. I review the range of experiments, describing the current state of our understanding of the observed acceleration, and speculate about future progress in understanding Dark Energy.

scholarly journals A dark energy quintessence model of the universe

2019 ◽  
Vol 35 (04) ◽  
pp. 2050002
Author(s):  
G. K. Goswami ◽  
Anirudh Pradhan ◽  
A. Beesham
Keyword(s):  
Dark Energy ◽  
Deceleration Parameter ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Time Dependent ◽  
Observational Constraints ◽  
History Of ◽  
Flrw Universe ◽  
The Universe ◽  
Quintessence Model

In this paper, we have presented a model of the Friedmann–Lemaitre–Robertson–Walker (FLRW) universe filled with matter and dark energy (DE) fluids by assuming an ansatz that deceleration parameter (DP) is a linear function of the Hubble constant. This results in a time-dependent DP having decelerating–accelerating transition phase of the universe. This is a quintessence model [Formula: see text]. The quintessence phase remains for the period [Formula: see text]. The model is shown to satisfy current observational constraints. Various cosmological parameters relating to the history of the universe have been investigated.

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