scholarly journals The effects of spatial curvature on cosmic evolution

2017 ◽  
Vol 26 (10) ◽  
pp. 1750115 ◽  
Author(s):  
Christine R. Farrugia ◽  
Joseph Sultana
Keyword(s):  
Dark Energy ◽  
Density Parameter ◽  
Closed Universe ◽  
Spatial Curvature ◽  
Energy Models ◽  
Cosmic Evolution ◽  
Cosmological Scenario ◽  
Opposite Behavior ◽  
The Universe ◽  
Dynamical Dark Energy

As evidenced by a great number of works in the literature, it is common practice to assume that the universe is flat. However, the majority of studies which make use of observational data to constrain the curvature density parameter are premised on the [Formula: see text]CDM cosmology, or extensions thereof. On the other hand, when data is fitted to models with a time-varying dark energy equation-of-state, it turns out that such models may accommodate a non-flat universe. Several authors caution that if the assumption of spatial flatness is wrong, it could greatly hinder our understanding of dark energy, even if the curvature is in reality very small. We thus consider a number of different dynamical dark energy models that represent the complete cosmological scenario, and investigate the effects of spatial curvature on the evolution. We find that for a closed universe, the transition to the epoch of decelerated expansion would be delayed with respect to the flat case. So would the start of the current dark energy-dominated era. This would be accompanied by a larger inflationary acceleration, as well as a larger subsequent deceleration. The opposite behavior is observed if the universe is open.

scholarly journals COSMIC EVOLUTION WITH EARLY AND LATE ACCELERATION INSPIRED BY THE DUAL NATURE OF THE RICCI SCALAR CURVATURE

2008 ◽  
Vol 17 (05) ◽  
pp. 755-784 ◽  
Author(s):  
S. K. SRIVASTAVA
Keyword(s):  
Dark Energy ◽  
Scalar Curvature ◽  
Modified Gravity ◽  
Dual Nature ◽  
Intermediate Period ◽  
Cosmic Evolution ◽  
Cosmological Scenario ◽  
Current Value ◽  
In The Beginning ◽  
The Universe

In the present paper, a cosmological scenario is proposed in which dark energy emerges spontaneously from modified gravity. In this scenario, the universe inflates for ~10-37s in the beginning and the late universe accelerates after 8.58 Gyrs. During the long intermediate period, the universe decelerates driven by radiation and subsequently by matter. The gravitational dark energy that emerges in this model mimics quintessence and its density falls by 115 orders from 2.18 × 1068GeV4initially to its current value 2.19 × 10-47GeV4.

Cosmic expansion with curved dark energy cosmology: Inevitability of cosmic doomsday

2021 ◽  
pp. 2150048
Author(s):  
Chayanika Rabha ◽  
Sanjeev Kalita
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Spatial Curvature ◽  
Dark Energy Density ◽  
Future Evolution ◽  
Cosmic Expansion ◽  
Energy Models ◽  
Type Ia ◽  
Ia Supernovae ◽  
Dynamical Dark Energy

In this work, we have constructed deceleration–acceleration and future evolution of cosmic expansion with curved dynamical dark energy models. Closed and open spatial curvatures are calculated by assuming that dark energy density does not exceed 85% of the closure density and by obtaining lower bounds on the ratio of dark energy to matter density, in terms of equation of state of dark energy. The range of transition epoch [Formula: see text] realized for spatial curvature [Formula: see text] is consistent with model independent estimations coming from galactic ages, strong lensing, Type Ia supernovae and recent constraints coming from [Formula: see text] measurements in non-flat dynamical dark energy models. Two novel parametrizations of dark energy equation of state namely the logarithmic and oscillatory, which are singularity free at future point [Formula: see text] are used to study the deceleration parameter q(z). Irrespective of spatial curvature, cosmic doomsday has been found inevitable for both the parametrizations. The time evolution of logarithmic parametrization, being reminiscent of a quintom field (canonical[Formula: see text]phantom), is converted into dynamics of a canonical quintessence and a phantom field for the redshift range ([Formula: see text],[Formula: see text]) and ([Formula: see text], [Formula: see text]). It is found that irrespective of spatial curvature, the quintessence component becomes sub-dominant in future giving it’s way to the phantom component.

scholarly journals Taxonomy of Dark Energy Models

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 163
Author(s):  
Verónica Motta ◽  
Miguel A. García-Aspeitia ◽  
Alberto Hernández-Almada ◽  
Juan Magaña ◽  
Tomás Verdugo
Keyword(s):  
Dark Energy ◽  
Cold Dark Matter ◽  
Accelerated Expansion ◽  
Energy Component ◽  
The Past ◽  
Energy Models ◽  
The Status ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Unknown Component

The accelerated expansion of the Universe is one of the main discoveries of the past decades, indicating the presence of an unknown component: the dark energy. Evidence of its presence is being gathered by a succession of observational experiments with increasing precision in its measurements. However, the most accepted model for explaining the dynamic of our Universe, the so-called Lambda cold dark matter, faces several problems related to the nature of such energy component. This has led to a growing exploration of alternative models attempting to solve those drawbacks. In this review, we briefly summarize the characteristics of a (non-exhaustive) list of dark energy models as well as some of the most used cosmological samples. Next, we discuss how to constrain each model’s parameters using observational data. Finally, we summarize the status of dark energy modeling.

scholarly journals Physical Acceptability of the Renyi, Tsallis and Sharma-Mittal Holographic Dark Energy Models in the f(T,B) Gravity under Hubble’s Cutoff

Universe ◽  
2021 ◽  
Vol 7 (3) ◽  
pp. 67
Author(s):  
Salim Harun Shekh ◽  
Pedro H. R. S. Moraes ◽  
Pradyumn Kumar Sahoo
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
Field Equations ◽  
Eos Parameter ◽  
Two Fluids ◽  
Gravitational Field Equations ◽  
Energy Models ◽  
Different Types ◽  
The Universe

In the present article, we investigate the physical acceptability of the spatially homogeneous and isotropic Friedmann–Lemâitre–Robertson–Walker line element filled with two fluids, with the first being pressureless matter and the second being different types of holographic dark energy. This geometric and material content is considered within the gravitational field equations of the f(T,B) (where T is the torsion scalar and the B is the boundary term) gravity in Hubble’s cut-off. The cosmological parameters, such as the Equation of State (EoS) parameter, during the cosmic evolution, are calculated. The models are stable throughout the universe expansion. The region in which the model is presented is dependent on the real parameter δ of holographic dark energies. For all δ≥4.5, the models vary from ΛCDM era to the quintessence era.

GROWTH INDEX AND MODIFIED GRAVITY

2011 ◽  
Vol 01 ◽  
pp. 228-233
Author(s):  
YUNGUI GONG
Keyword(s):  
Growth Rate ◽  
Dark Energy ◽  
Modified Gravity ◽  
Growth Index ◽  
Accurate Approximation ◽  
Energy Models ◽  
Λcdm Model ◽  
The Universe ◽  
Matter Energy ◽  
Matter Perturbation

The growth rate of matter perturbation and the expansion rate of the Universe can be used to distinguish modified gravity and dark energy models. Remarkably, the growth rate can be approximated as Ωγ. We discuss the dependence of the growth index γ on the dimensionless matter energy density Ω for a more accurate approximation of the growth factor. The observational data are used to fit different models. The data strongly disfavor the Dvali-Gabadadze-Porrati model. For the ΛCDM model, we find that [Formula: see text]. For the Dvali-Gabadadze-Porrati model, we find that [Formula: see text].

scholarly journals Testing for dynamical dark energy models with redshift-space distortions

2013 ◽  
Vol 2013 (01) ◽  
pp. 030-030 ◽  
Author(s):  
Shinji Tsujikawa ◽  
Antonio De Felice ◽  
Jailson Alcaniz
Keyword(s):  
Dark Energy ◽  
Energy Models ◽  
Dynamical Dark Energy

scholarly journals QCD MODIFIED GHOST SCALAR FIELD DARK ENERGY MODELS

2013 ◽  
Vol 22 (05) ◽  
pp. 1350018 ◽  
Author(s):  
K. KARAMI ◽  
S. ASADZADEH ◽  
M. MOUSIVAND ◽  
Z. SAFARI
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Linear Perturbation ◽  
Density Parameter ◽  
Frw Cosmology ◽  
Frw Universe ◽  
Ghost Dark Energy ◽  
Energy Models ◽  
Scalar Field Models ◽  
Ghost Scalar Field

Within the framework of FRW cosmology, we study the QCD modified ghost scalar field models of dark energy (DE) in the presence of both interaction and viscosity. For a spatially nonflat FRW universe containing modified ghost dark energy (MGDE) and dark matter (DM), we obtain the equation of state of MGDE, the deceleration parameter as well as a differential equation governing the MGDE density parameter. We also investigate the growth of structure formation for our model in a linear perturbation regime. Furthermore, we reconstruct both the dynamics and potentials of the quintessence, tachyon, K-essence and dilaton scalar field DE models according to the evolution of the MGDE density.

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.

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