Variable deceleration parameter and dark energy models

2016 ◽  
Vol 13 (05) ◽  
pp. 1650055 ◽  
Author(s):  
Binaya K. Bishi

This paper deals with the Bianchi type-III dark energy model and equation of state parameter in a first class of [Formula: see text] gravity. Here, [Formula: see text] and [Formula: see text] represents the Ricci scalar and trace of the energy momentum tensor, respectively. The exact solutions of the modified field equations are obtained by using (i) linear relation between expansion scalar and shear scalar, (ii) linear relation between state parameter and skewness parameter and (iii) variable deceleration parameter. To obtain the physically plausible cosmological models, the variable deceleration parameter with the suitable substitution leads to the scale factor of the form [Formula: see text], where [Formula: see text] and [Formula: see text] are arbitrary constants. It is observed that our models are accelerating for [Formula: see text] and for [Formula: see text], transition phase from deceleration to acceleration. Further, we have discussed physical properties of the models.

2020 ◽  
Vol 17 (10) ◽  
pp. 2050160
Author(s):  
H. Eser ◽  
C. B. Kilinc

In this paper, we study spatially homogeneous and anisotropic Bianchi type-V and IX universes filled with interacting dark matter and holographic dark energy. We obtained the solution of the field equations by using the variable deceleration parameter in the form [Formula: see text]. The cosmological parameters of the models like deceleration and equation of state are obtained. We observe that the deceleration parameter tends to [Formula: see text] which shows an accelerated universe, and the equation of state tends to [Formula: see text] which belongs to [Formula: see text]CDM model. Moreover, we establish the correspondence between holographic dark energy model and quintessence scalar field.


2020 ◽  
Vol 80 (12) ◽  
Author(s):  
M. Vijaya Santhi ◽  
Y. Sobhanbabu

AbstractIn this paper, we have investigated Tsallis holographic dark energy (infrared cutoff is the Hubble radius) in homogeneous and anisotropic Bianchi type-III Universe within the framework of Saez–Ballester scalar–tensor theory of gravitation. We have constructed non-interaction and interaction dark energy models by solving the Saez–Ballester field equations. To solve the field equations, we assume a relationship between the metric potentials of the model. We developed the various cosmological parameters (namely deceleration parameter q, equation of state parameter $$\omega _t$$ ω t , squared sound speed $$v_s^2$$ v s 2 , om-diagnostic parameter Om(z) and scalar field $$\phi $$ ϕ ) and well-known cosmological planes (namely $$\omega _t-\omega _t^{'}$$ ω t - ω t ′ plane, where $$'$$ ′ denotes derivative with respect to ln(a) and statefinders ($$r-s$$ r - s ) plane) and analyzed their behavior through graphical representation for our both the models. It is also, quite interesting to mention here that the obtained results are coincide with the modern observational data.


2019 ◽  
Vol 34 (13) ◽  
pp. 1950098 ◽  
Author(s):  
Can Aktaş

In this paper, we have researched tachyon field, k-essence and quintessence dark energy (DE) models for Friedmann–Robertson–Walker (FRW) universe with varying G and [Formula: see text] in f(R, T) gravitation theory. The theory of f(R, T) is proposed by Harko et al. [Phys. Rev. D 84, 024020, 2011]. In this theory, R is the Ricci scalar and T is the trace of energy–momentum tensor. For the solutions of field equations, we have used linearly varying deceleration parameter (LVDP), the equation of state (EoS) and the ratio between [Formula: see text] and Hubble parameter. Also, we have discussed some physical behavior of the models with various graphics.


2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
M. Sharif ◽  
M. Zubair

We develop the connection off(R)theory with new agegraphic and holographic dark energy models. The functionf(R)is reconstructed regarding thef(R)theory as an effective description for these dark energy models. We show the future evolution offand conclude that these functions represent distinct pictures of cosmological eras. The cosmological parameters such as equation of state parameter, deceleration parameter, statefinder diagnostic, andw−w′analysis are investigated which assure the evolutionary paradigm off.


2017 ◽  
Vol 95 (4) ◽  
pp. 381-392 ◽  
Author(s):  
M. Vijaya Santhi ◽  
V.U.M. Rao ◽  
Y. Aditya

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.


2017 ◽  
Vol 95 (2) ◽  
pp. 179-183 ◽  
Author(s):  
M. Vijaya Santhi ◽  
V.U.M. Rao ◽  
Y. Aditya

In this paper, we consider Bianchi type-VI0 space–time filled with anisotropic modified holographic Ricci dark energy in a scalar–tensor theory proposed by Brans–Dicke (Phys. Rev. 124, 925 (1961)). The field equations in this scalar–tensor theory, have been solved for the following physically relevant assumptions: (i) the scalar field ([Formula: see text]) is proportional to average scale factor (a(t)), (ii) expansion scalar (θ) in the model is proportional to shear scalar (σ). It has been observed that the presented universe is in an accelerating phase at the present epoch, which is in good agreement with the recent astronomical observations. We have also discussed some other properties of the obtained model.


2021 ◽  
Vol 81 (11) ◽  
Author(s):  
Y. Sobhanbabu ◽  
M. Vijaya Santhi

AbstractIn this work devoted to the investigation of the Tsallis holographic dark energy (IR cut-off is Hubble radius) in homogeneous and anisotropic Kantowski–Sachs Universe within the frame-work of Saez–Ballester scalar tensor theory of gravitation. We have constructed non-interacting and interacting Tsallis holographic dark energy models by solving the field equations using the relationship between the metric potentials. This relation leads to a viable deceleration parameter model which exhibits a transition of the Universe from deceleration to acceleration. In interacting case, we focus on sign-changeable interaction between Tsallis holographic dark energy and dark matter. The dynamical parameters like equation of state parameter, energy densities of Tsallis holographic dark energy and dark matter, deceleration parameter, and statefinder parameters of the models are explained through graphical representation. And also, we discussed the stability analysis of the our models.


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