Bouncing scenario in Brans–Dicke theory

2020 ◽  
Vol 17 (04) ◽  
pp. 2050056
Author(s):  
Sunil Kumar Tripathy ◽  
Subingya Pandey ◽  
Alaka Priyadarsini Sendha ◽  
Dipanjali Behera
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Equation Of State ◽  
Linear Equation ◽  
Scale Factor ◽  
Cosmic Acceleration ◽  
Late Time ◽  
Dark Fluid

A bouncing scenario is studied in the framework of generalized Brans–Dicke theory. In order to have a dark energy (DE) driven late time cosmic acceleration, we have considered a unified dark fluid simulated by a linear equation of state (EoS). The evolutionary behavior of the DE equation of parameter derived from the unified dark fluid has been discussed. The effect of the bouncing scale factor on the Brans–Dicke parameter, self-interacting potential and the Brans–Dicke scalar field is investigated.

Kaluza–Klein dark energy model in the form of wet dark fluid in f(R, T) gravity

2014 ◽  
Vol 92 (9) ◽  
Author(s):  
P.K. SAHOO ◽  
B. Mishra
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Accelerated Expansion ◽  
Physical Parameters ◽  
Late Time ◽  
Field Equations ◽  
Wet Dark Fluid ◽  
Dark Fluid ◽  
The Universe ◽  
Kaluza Klein

A five dimensional Kaluza-Klein space time is considered with wet dark fluid (WDF) source in the framework of f(R,T) gravity, where R is the Ricci scalar and T is the trace of the energy-momentum tensor proposed by Harko et al. (Phys. Rev. D \textbf{84}, 024020, (2011)). A new equation of state in the form of WDF has been used for dark energy (DE) component of the universe. It is modeled on the equation of state p=\omega(\rho-\rho^*) which can be describing a liquid, for example water. The exact solutions to the corresponding field equations are obtained for power law and exponential law of the volumetric expansion. The geometrical and physical parameters for both the models are studied. The model obtained here may represent the inflationary era in the early universe and the very late time of the universe. This model obtained here shows that even in the presence of wet dark fluid, the universe indicates accelerated expansion of the universe.

Kaluza–Klein dark energy model in the form of wet dark fluid in f(R, T) gravity

2014 ◽  
Vol 92 (9) ◽  
pp. 1062-1067 ◽  
Author(s):  
P. K. Sahoo ◽  
B. Mishra
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Accelerated Expansion ◽  
Physical Parameters ◽  
Late Time ◽  
Field Equations ◽  
Wet Dark Fluid ◽  
Dark Fluid ◽  
The Universe ◽  
Kaluza Klein

In this paper, we have investigated the five-dimensional Kaluza–Klein space time with wet dark fluid (WDF), which is a candidate for dark energy (DE), in the framework of f(R, T) gravity. R and T denote the Ricci scalar and the trace of the energy–momentum tensor, respectively (Harko et al. Phys. Rev. D, 84, 024020 (2011)). We have used equation of state in the form of WDF for the DE component of the universe. It is modeled on the equation of state p = ω(ρ – ρ*). With the help of the power law and exponential law of volumetric expansion, we have derived the exact solutions of the corresponding field equations. The geometrical and physical parameters for both the models are studied. The model obtained here may represent the inflationary era in the early universe and very late time of the universe. It is concluded that the model obtained here shows that even in the presence of WDF, the universe indicates accelerated expansion of the universe.

Scale factor — Cosmic time relation and occurrences of future cosmic singularities with different redshift parametrizations of dark energy EoS-s

2019 ◽  
Vol 34 (28) ◽  
pp. 1950228
Author(s):  
Swetalina Bhowmik ◽  
Ritabrata Biswas
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Cosmic Time ◽  
Scale Factor ◽  
Late Time ◽  
Expanding Universe ◽  
Unknown Parameters ◽  
Time Relation

While modeling our late time cosmically accelerated universe, it is popular to involve different dark energy (DE) models, the equation of state (EoS) of which can be taken as a function of the redshift and some unknown parameters. Barboza and Alcaniz have proposed one such kind of DE EoS model. We use some new parametrizations like Feng, Shen, Li, Li I and II and Polynomial parametrizations to get more accurate concepts about the fate of our expanding universe. We try to find how the hypothesis of the fate of our universe behaves in the above background of DE models. Possibilities of occurrences of future cosmic singularities are studied.

scholarly journals Chaplygin-gas solutions of f(R) gravity

2016 ◽  
Vol 13 (10) ◽  
pp. 1650120 ◽  
Author(s):  
Maye Elmardi ◽  
Amare Abebe ◽  
Abiy Tekola
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Early Universe ◽  
Equations Of State ◽  
Initial Conditions ◽  
Exact Formula ◽  
Chaplygin Gas ◽  
Cosmic Acceleration ◽  
Late Time ◽  
Modified Chaplygin Gas

We explore exact [Formula: see text] gravity solutions that mimic Chaplygin-gas inspired [Formula: see text]CDM cosmology. Starting with the original, generalized and modified Chaplygin-gas (MCG) equations of state (EoS), we reconstruct the forms of [Formula: see text] Lagrangians. The resulting solutions are generally quadratic in the Ricci scalar, but have appropriate [Formula: see text]CDM solutions in limiting cases. These solutions, given appropriate initial conditions, can be potential candidates for scalar field-driven early universe expansion (inflation) and dark energy-driven late-time cosmic acceleration.

A new potential for scalar field dark energy

2020 ◽  
Vol 17 (09) ◽  
pp. 2050139
Author(s):  
Abdulla Al Mamon
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Equation Of State ◽  
Hubble Parameter ◽  
Time Derivative ◽  
Field Potential ◽  
State Parameter ◽  
Simple Relation ◽  
Scale Factor ◽  
Equation Of State Parameter

In this paper, we have investigated some cosmological consequences of a quintessence dark energy model. In particular, we have obtained the forms of the equation of state parameter, the deceleration parameter and the field potential by considering a simple relation between the scale factor and the time derivative of the scalar field, instead of assuming any functional form for the scalar field potential or the scale factor or the equation of state parameter. We have found that the model provides the desired early deceleration followed by present acceleration of the universe. The potential derived numerically in this work in the form [Formula: see text], where [Formula: see text], [Formula: see text] and [Formula: see text] are real constant parameters. It has also been found that our model mimics as the standard [Formula: see text]CDM model in future. Finally, we have also shown the evolution of the normalized Hubble parameter for our model and the [Formula: see text]CDM model and compared that with the latest Hubble parameter data.

Cosmology of viscous holographic f(G) gravity and consequences in the framework of quintessence scalar field

2019 ◽  
Vol 16 (11) ◽  
pp. 1950176
Author(s):  
Swati Sinha ◽  
Surajit Chattopadhyay ◽  
Irina Radinschi
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Equation Of State ◽  
Holographic Dark Energy ◽  
Inhomogeneous Equation ◽  
Late Time ◽  
Effective Equation ◽  
Future Singularity ◽  
Warm Inflation ◽  
The Universe

Work reported in this study demonstrates the reconstruction schemes for the [Formula: see text] gravity in the framework of bulk viscosity and holographic background evolution by considering the universe filled by the viscous fluid that is just special class of more general fluids as described in Nojiri and Odintsov [Inhomogeneous equation of state of the universe: Phantom era, future singularity, and crossing the phantom barrier, Phys. Rev. D 72 (2005) 023003]. The bulk viscous pressure has been considered as [Formula: see text], with [Formula: see text]. Considering the scale factor in power law form and taking holographic dark energy (HDE) with density [Formula: see text] and generalized extended holographic dark energy (EGHRDE) with density [Formula: see text], a specific case of Nojiri–Odintsov holographic DE ([Unifying phantom inflation with late-time acceleration: Scalar phantom–non-phantom transition model and generalized holographic dark energy, Gen. Relativ. Gravit. 38 (2006) 1285]) we have derived solutions for [Formula: see text] and the subsequent effective equation of state parameters have been found to behave like quintom irrespective of the choice of [Formula: see text]. Finally, considering [Formula: see text] as quintessence scalar field we have explored the possibility of quasi-exponential expansion and warm inflation.

Tsallis holographic dark energy in Bianchi type-III spacetime with scalar fields

2019 ◽  
Vol 34 (37) ◽  
pp. 1950310 ◽  
Author(s):  
Murat Korunur
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Bianchi Type ◽  
Holographic Dark Energy ◽  
Scalar Fields ◽  
Cosmic Acceleration ◽  
Late Time ◽  
Acceleration Phase ◽  
Eos Parameter ◽  
Type Iii

In this paper, we study one of the new dark energy models named Tsallis holographic dark energy (THDE) model considering the Bianchi type-III spacetime model. Considering deceleration parameter, transition from deceleration to acceleration phase happens at [Formula: see text]. The equation of state (EoS) parameter has been found using the Granda–Oliveros (GO) scale. It is found that for [Formula: see text] values, EoS parameter behaves like the quintessence era; for [Formula: see text], EoS parameter behaves like the phantom dark energy and approaches [Formula: see text]CDM model at late-time cosmic acceleration phase. Also, we reconstructed a correspondence between THDE model and some well-known scalar fields, such as tachyon, quintessence and [Formula: see text]-essence. In addition, we evaluated equation of state parameter, kinetic energy and scalar potential versus time.

Bianchi type-III holographic dark energy model with quintessence

2018 ◽  
Vol 15 (09) ◽  
pp. 1850161 ◽  
Author(s):  
M. Vijaya Santhi ◽  
V. U. M. Rao ◽  
Daba Meshesha Gusu ◽  
Y. Aditya
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Equation Of State ◽  
Dark Energy Model ◽  
Bianchi Type ◽  
Holographic Dark Energy ◽  
Scale Factor ◽  
Holographic Dark Energy Model ◽  
The Universe ◽  
Average Scale Factor

In this study, we investigate an anisotropic Bianchi type-[Formula: see text] space-time in the presence of matter and holographic dark energy components within the framework of general relativity. We obtained the solution of the field equations by assuming (i) the expansion scalar [Formula: see text] in the model is proportional to shear scalar [Formula: see text], (ii) hybrid expansion law for average scale factor (keeping an eye on the recent scenario of accelerating nature of the universe). We develop cosmological parameters like deceleration and equation of state parameters. These parameters are plotted versus redshift [Formula: see text] for different values of power component of average scale factor [Formula: see text]. We observe that the equation of state varies in quintessence region ([Formula: see text]) and ultimately tends to [Formula: see text]CDM model ([Formula: see text]). The deceleration parameter exhibits a smooth transition from early decelerated epoch to present accelerated era. In addition, we establish the correspondence between our holographic dark energy model and quintessence scalar field. We also express the self-interacting potential [Formula: see text] and scalar field [Formula: see text] of quintessence model as functions of cosmic time [Formula: see text], which describes the accelerated expansion of the universe.

scholarly journals DARK ENERGY, WITH SIGNATURES

2010 ◽  
Vol 19 (14) ◽  
pp. 2325-2330
Author(s):  
SOURISH DUTTA ◽  
ROBERT J. SCHERRER ◽  
STEPHEN D. H. HSU
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Energy Scale ◽  
Fine Tuning ◽  
Time Dependent ◽  
Late Time ◽  
Particle Content ◽  
Energy Field ◽  
Energy Models ◽  
New Energy

We propose a class of simple dark energy models which predict a late-time dark radiation component and a distinctive time-dependent equation of state w(z) for redshift z < 3. The dark energy field can be coupled strongly enough to standard model particles to be detected in colliders, and the model requires only modest additional particle content and little or no fine-tuning other than a new energy scale of order milli-electron volts.

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