Study of cosmological evolution via GGPDE f(R) models

2021 ◽  
Vol 18 (03) ◽  
pp. 2150043
Author(s):  
Iqra Nawazish ◽  
Wajiha Javed ◽  
Ertan Güdekli ◽  
G. Abbas
Keyword(s):  
Equation Of State ◽  
Speed Of Sound ◽  
Dark Energy Model ◽  
Cosmological Parameters ◽  
Graphical Analysis ◽  
Frw Universe ◽  
Shift Parameter ◽  
Pilgrim Dark Energy ◽  
Scale Factors ◽  
Cosmic Evolution

This paper examines the cosmic evolution and current expansion for flat FRW universe through generalized ghost pilgrim dark energy model in [Formula: see text] gravity. For this purpose, we reconstruct the models in terms of red-shift parameter with respect to three scale factors, i.e. power-law, intermediate and a scale factor defining two unified phases. We study compatibility of reconstructed [Formula: see text] models through [Formula: see text]-[Formula: see text] planes whereas graphical analysis of squared speed of sound leads to investigate their stability. We also explore the behavior of cosmological parameters such as equation of state and deceleration parameters. Moreover, we study the existence of freezing/thawing regions via [Formula: see text]-[Formula: see text] planes. We conclude that squared speed of sound identifies both stability/instability of reconstructed [Formula: see text] models while equation of state and deceleration parameters specifies transition from decelerated to accelerated expanding cosmos. The [Formula: see text]-[Formula: see text] planes discover thawing as well as freezing regions for particular values of pilgrim parameter.

scholarly journals Cosmological aspects of sound speed parameterizations in fractal universe

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
Abdul Jawad ◽  
Sadaf Butt ◽  
Shamaila Rani ◽  
Khadija Asif
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Speed Of Sound ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Graphical Analysis ◽  
Eos Parameter ◽  
Energy Models ◽  
Equation Of State Parameter ◽  
The Universe

AbstractIn the framework of fractal universe, the unified models of dark energy and dark matter are being presented with the background of homogenous and isotropic FLRW geometry. The aspects of fractal cosmology helps in better understanding of the universe in different dimensions. Relationship between the squared speed of the sound and the equation of state parameter is the key feature of these models. We have used constant as well as variable forms of speed of sound and express it as a function of equation of state parameter. By utilizing the four different forms of speed of sound, we construct the energy densities and pressures for these models and then various cosmological parameters like hubble parameter, EoS parameter, deceleration parameter and Om- diagnostic are investigated. Graphical analysis of these parameters show that in most of the cases EoS parameters and trajectories of Om-diagnostic corresponds to the quintessence like nature of the universe and the deceleration parameters represent accelerated and decelerated phase. In the end, we remark that cosmological analysis of these models indicates that these models correspond to different well known dark energy models.

scholarly journals Evolution of non-flat cosmos via GGPDE f(R) model

2020 ◽  
Vol 80 (2) ◽  
Author(s):  
Wajiha Javed ◽  
Iqra Nawazish ◽  
Fatima Shahid ◽  
Nimra Irshad
Keyword(s):  
Dark Energy ◽  
Power Law ◽  
Dark Energy Model ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Scale Factor ◽  
Energy Model ◽  
Density Parameter ◽  
Shift Parameter ◽  
Scale Factors

Abstract This paper is devoted to explore the cosmic evolution of non-flat Friedmann Robertson Walker universe through generalized ghost pilgrim dark energy model in the background of f(R) gravity. For this purpose, we consider two well known scale factors, i.e., power-law and unified scale factors in terms of red shift parameter. For these scale factors, we reconstruct the given dark energy model in f(R) gravity and determine its stability/instability through squared speed of sound parameter. In order to discuss the behavior of reconstructed and dark energy models, we evaluate well known cosmological parameter such as equation of state parameter along with $$\omega $$ω–$$\omega '$$ω′ plane. In addition to this, we also investigate compatibility of new models with standard cosmological models through state-finder parameters. The density parameter is formulated for both ordinary matter as well as dark energy components and results are compared with Planck 2018 constraints. It is concluded that cosmological parameters reveal consistency with recent observations while the value of density parameter suggested by Planck 2018 is achieved by power-law scale factor in most of the cases as compared to unified scale factor.

Cosmic evolution of ghost dark energy models in f(G,T) gravity

2019 ◽  
Vol 35 (10) ◽  
pp. 2050063
Author(s):  
M. Sharif ◽  
Saadia Saba
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Speed Of Sound ◽  
Dark Energy Model ◽  
State Parameter ◽  
Energy Model ◽  
Frw Universe ◽  
Ghost Dark Energy ◽  
Energy Models ◽  
Generalized Ghost Dark Energy

The aim of this paper is to study the reconstruction paradigm for both ghost as well as generalized ghost dark energy models in the context of [Formula: see text] gravity. To accomplish this, we use correspondence scenario for pressureless flat FRW universe with power-law scale factor. The cosmological behavior of reconstructed models is analyzed through graphical analysis of deceleration, equation of state, squared speed of sound parameters and phase planes. It is found that the deceleration parameter represents accelerated epoch for both models whereas equation of state parameter indicates phantom era of the universe for ghost dark energy model and quintessence for its generalized version. The phase planes [Formula: see text] and [Formula: see text] indicate the freezing region with phantom phase for both reconstructed dark energy models. We conclude that the squared speed of sound parameter leads to the stability of generalized ghost dark energy model only.

scholarly journals Cosmological Analysis of Dynamical Chern-Simons Modified Gravity via Dark Energy Scenario

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
Abdul Jawad ◽  
Shamaila Rani
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Speed Of Sound ◽  
Modified Gravity ◽  
Cold Dark Matter ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Pilgrim Dark Energy ◽  
Energy Scenario ◽  
Chern Simons

The purpose of this paper is to study the cosmological evolution of the universe in the framework of dynamical Chern-Simons modified gravity. We take pilgrim dark energy model with Hubble and event horizons in interacting scenario with cold dark matter. For this scenario, we discuss cosmological parameters such as Hubble and equation of state and cosmological plane likeωϑ-ωϑ′and squared speed of sound. It is found that Hubble parameter approaches the ranges75-0.5+0.5(foru=2) and (74, 74.30) (foru=1,-1,-2) for Hubble horizon pilgrim dark energy. It implies the ranges74.80-0.005+0.005(foru=2) and (73.4, 74) (foru=-2) for event horizon pilgrim dark energy. The equation of state parameter provides consistent ranges with different observational schemes. Also,ωϑ-ωϑ′planes lie in the range (ωϑ=-1.13-0.25+0.24,ωϑ′<1.32). The squared speed of sound shows stability for all present models in the present scenario. We would like to mention here that our results of various cosmological parameters show consistency with different observational data like Planck, WP, BAO,H0, SNLS, and WMAP.

Interacting and noninteracting dark energy models in f(R) gravity

2018 ◽  
Vol 27 (09) ◽  
pp. 1850091 ◽  
Author(s):  
M. Sharif ◽  
Iqra Nawazish
Keyword(s):  
Dark Energy ◽  
Positive Curvature ◽  
Cosmological Parameters ◽  
Effective Equation ◽  
Frw Universe ◽  
Shift Parameter ◽  
Energy Models ◽  
Cosmic Evolution ◽  
Curvature Parameter ◽  
The Stability

In this paper, we study cosmic evolution and current expansion via generalized ghost pilgrim dark energy (PDE) model for FRW universe in [Formula: see text] gravity. For this purpose, we consider both interacting and non-interacting forms of dark energy (DE) model and reconstruct [Formula: see text] model using red-shift parameter. In order to analyze the effects of the DE model, we formulate some standard cosmological parameters such as Hubble, effective equation of state (EoS) and statefinder parameters as well as [Formula: see text]–[Formula: see text] plane. We also investigate the stability criteria for both interacting and noninteracting models through the squared speed of sound. It is concluded that the best-fit results are found for the positive curvature parameter in the presence of the noninteracting model. For the interacting model, the cosmic evolution is well explained by closed and open universe models while the flat geometry effectively describes the current cosmos.

scholarly journals Almost-Pseudo-Ricci Symmetric FRW Universe with a Dynamic Cosmological Term and Equation of State

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 205
Author(s):  
Sanjay Mandal ◽  
Avik De ◽  
Tee-How Loo ◽  
Pradyumn Kumar Sahoo
Keyword(s):  
Equation Of State ◽  
Cosmological Parameters ◽  
Cosmological Term ◽  
Ricci Scalar ◽  
Energy Conditions ◽  
Late Time ◽  
Frw Universe ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Universe

The objective of the present paper is to investigate an almost-pseudo-Ricci symmetric FRW spacetime with a constant Ricci scalar in a dynamic cosmological term Λ(t) and equation of state (EoS) ω(t) scenario. Several cosmological parameters are calculated in this setting and thoroughly studied, which shows that the model satisfies the late-time accelerating expansion of the universe. We also examine all of the energy conditions to check our model’s self-stability.

Viability of specific reconstructed f(T,𝒯 ) models

2019 ◽  
Vol 34 (30) ◽  
pp. 1950184
Author(s):  
M. Umair Shahzad ◽  
Nadeem Azhar ◽  
Abdul Jawad ◽  
Shamaila Rani
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Dark Energy Model ◽  
State Parameter ◽  
Pilgrim Dark Energy ◽  
Ghost Dark Energy ◽  
Energy Models ◽  
Equation Of State Parameter ◽  
Hubble Horizon ◽  
The Universe

The reconstruction scenario of well-established dark energy models such as pilgrim dark energy model and generalized ghost dark energy with Hubble horizon and [Formula: see text] models is being considered. We have established [Formula: see text] models and analyzed their viability through equation of state parameter and [Formula: see text] (where prime denotes derivative with respect to [Formula: see text]) plane. The equation of state parameter evolutes the universe in three different phases such as quintessence, vacuum and phantom. However, the [Formula: see text] plane also describes the thawing as well as freezing region of the universe. The recent observational data also favor our results.

scholarly journals Impact of generalized polytropic equation of state on charged anisotropic polytropes

2020 ◽  
Vol 80 (2) ◽  
Author(s):  
S. A. Mardan ◽  
M. Rehman ◽  
I. Noureen ◽  
R. N. Jamil
Keyword(s):  
Equation Of State ◽  
Speed Of Sound ◽  
Graphical Analysis ◽  
Maxwell Field ◽  
Anisotropic Fluid ◽  
Polytropic Index ◽  
Model Parameters ◽  
Field Equations ◽  
Polytropic Equation ◽  
Fluid Configuration

Abstract In this paper, generalized polytropic equation of state is used to get new classes of polytropic models from the solution of Einstein-Maxwell field equations for charged anisotropic fluid configuration. The models are developed for different values of polytropic index $$n=1,~\frac{1}{2},~2$$n=1,12,2. Masses and radii of eight different stars have been regained with the help of developed models. The speed of sound technique and graphical analysis of model parameters is used for the viability of developed models. The analysis of models indicates they are well behaved and physically viable.

scholarly journals HOLOGRAPHIC DARK ENERGY MODEL CHARACTERIZED BY THE CONFORMAL-AGE-LIKE LENGTH

2012 ◽  
Vol 27 (16) ◽  
pp. 1250085 ◽  
Author(s):  
ZHUO-PENG HUANG ◽  
YUE-LIANG WU
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Energy Density ◽  
Dark Energy Model ◽  
Holographic Dark Energy ◽  
Dimensional Space ◽  
Early Time ◽  
Energy Model ◽  
Holographic Dark Energy Model ◽  
Frw Universe

A holographic dark energy model characterized by the conformal-age-like length scale [Formula: see text] is motivated from the four-dimensional space–time volume at cosmic time t in the flat Friedmann–Robertson–Walker (FRW) universe. It is shown that when the background constituent with constant equation of state wm dominates the universe in the early time, the fractional energy density of the dark energy scales as [Formula: see text] with the equation of state given by [Formula: see text]. The value of wm is taken to be wm≃-1 during inflation, wm = ⅓ in radiation-dominated epoch and wm = 0 in matter-dominated epoch, respectively. When the model parameter d takes the normal value at order one, the fractional density of dark energy is naturally negligible in the early universe, Ω de ≪1 at a ≪1. With such an analytic feature, the model can be regarded as a single-parameter model like the ΛCDM model, so that the present fractional energy density Ω de (a = 1) can solely be determined by solving the differential equation of Ωde once d is given. We further extend the model to the general case in which both matter and radiation are present. The scenario involving possible interaction between the dark energy and the background constituent is also discussed.

Generalized ghost pilgrim dark energy in F(T,TG) cosmology

2016 ◽  
Vol 31 (25) ◽  
pp. 1650148 ◽  
Author(s):  
M. Sharif ◽  
Kanwal Nazir
Keyword(s):  
Dark Energy ◽  
Scale Factor ◽  
The Other ◽  
Frw Universe ◽  
Eos Parameter ◽  
Pilgrim Dark Energy ◽  
Pde Model ◽  
Scale Factors ◽  
Two Phases ◽  
Friedmann Robertson Walker

This paper is devoted to study the generalized ghost pilgrim dark energy (PDE) model in [Formula: see text] gravity with flat Friedmann–Robertson–Walker (FRW) universe. In this scenario, we reconstruct [Formula: see text] models and evaluate the corresponding equation of state (EoS) parameter for different choices of the scale factors. We assume power-law scale factor, scale factor for unification of two phases, intermediate and bouncing scale factor. We study the behavior of reconstructed models and EoS parameters graphically. It is found that all the reconstructed models show decreasing behavior for PDE parameter [Formula: see text]. On the other hand, the EoS parameter indicates transition from dust-like matter to phantom era for all choices of the scale factor except intermediate for which this is less than [Formula: see text]. We conclude that all the results are in agreement with PDE phenomenon.

Sign in / Sign up

Export Citation Format

Share Document