scholarly journals Constraints on Non-Flat Starobinsky f(R) Dark Energy Model

Entropy ◽  
2021 ◽  
Vol 23 (10) ◽  
pp. 1320
Author(s):  
Chao-Qiang Geng ◽  
Yan-Ting Hsu ◽  
Jhih-Rong Lu
Keyword(s):  
Dark Energy ◽  
Observational Data ◽  
Gravity Model ◽  
Dark Energy Model ◽  
Free Parameter ◽  
Energy Model ◽  
Density Parameter ◽  
Model Parameter ◽  
Best Fitting ◽  
Characteristic Curvature

We study the viable Starobinsky f(R) dark energy model in spatially non-flat FLRW backgrounds, where f(R)=R−λRch[1−(1+R2/Rch2)−1] with Rch and λ representing the characteristic curvature scale and model parameter, respectively. We modify CAMB and CosmoMC packages with the recent observational data to constrain Starobinsky f(R) gravity and the density parameter of curvature ΩK. In particular, we find the model and density parameters to be λ−1<0.283 at 68% C.L and ΩK=−0.00099−0.0042+0.0044 at 95% C.L, respectively. The best χ2 fitting result shows that χf(R)2≲χΛCDM2, indicating that the viable f(R) gravity model is consistent with ΛCDM when ΩK is set as a free parameter. We also evaluate the values of AIC, BIC and DIC for the best fitting results of f(R) and ΛCDM models in the non-flat universe.

scholarly journals CONSTRAINTS ON THAWING SCALAR FIELD MODELS FROM FUNDAMENTAL CONSTANTS

2013 ◽  
Vol 22 (07) ◽  
pp. 1350035 ◽  
Author(s):  
QING GAO ◽  
YUNGUI GONG
Keyword(s):  
Fine Structure ◽  
Dark Energy ◽  
Scalar Field ◽  
Observational Data ◽  
Dark Energy Model ◽  
Structure Constant ◽  
Energy Model ◽  
Fine Structure Constant ◽  
Density Parameter ◽  
Scalar Field Models

We consider a dark energy model with a relation between the equation of state parameter w and the energy density parameter Ωϕ derived from thawing scalar field models. Assuming the variation of the fine structure constant is caused by dark energy, we use the observational data of the variation of the fine structure constant to constrain the current value of w0 and Ωϕ0 for the dark energy model. At the 1σ level, the observational data excluded some areas around w0 = –1, which explains the positive detection of the variation of the fine structure constant at the 1σ level, but ΛCDM model is consistent with the data at the 2σ level.

scholarly journals Observational constraints on interacting Tsallis holographic dark energy model

2019 ◽  
Vol 79 (9) ◽  
Author(s):  
Ehsan Sadri
Keyword(s):  
Dark Energy ◽  
Observational Data ◽  
Dark Energy Model ◽  
Large Scale ◽  
Gamma Ray ◽  
Holographic Dark Energy ◽  
Energy Model ◽  
Late Time ◽  
Acoustic Oscillations ◽  
Holographic Dark Energy Model

Abstract In this paper, we investigate a recent proposed model – so called the Tsallis holographic dark energy (THDE) model with consideration of the Hubble and the event future horizon as IR cutoffs. In this case, we consider the non-gravitational and phenomenological interaction between dark sectors. We fit the free parameters of the model using Pantheon Supernovae Type Ia data, Baryon Acoustic Oscillations, Cosmic Microwave Background, Gamma-Ray burst and the the local value of the Hubble constant. We examine the THDE model to check its compatibility with observational data using objective Information Criterion (IC). We find that the THDE models cannot be supported by observational data once the $$\Lambda $$ΛCDM is considered as the referring model. Therefore we re-examine the analysis with the standard holographic dark energy model (HDE) as another reference. Changing the $$\Lambda $$ΛCDM to main standard dark energy model (HDE), we observe the compatibility of the THDE models. Using the Alcock–Paczynski (AP) test we check the deviation of the model compared to $$\Lambda $$ΛCDM and HDE. Surveying the evolution of squared of sound speed $$v^2_s$$vs2 as an another test we check the stability of the interacting and non-interacting THDE models and we find that while the THDE model with the Hubble horizon as IR cutoff is unstable against the background perturbation, the future event horizon as IR cutoff show stability at the late time. In addition, using the modified version of the CAMB package, we observe the suppressing the CMB spectrum at small K-modes and large scale.

scholarly journals Cosmological degeneracy versus cosmography: A cosmographic dark energy model

2017 ◽  
Vol 26 (03) ◽  
pp. 1750015 ◽  
Author(s):  
Orlando Luongo ◽  
Giovanni Battista Pisani ◽  
Antonio Troisi
Keyword(s):  
Dark Energy ◽  
Dark Energy Model ◽  
Free Parameter ◽  
Cold Dark Matter ◽  
Energy Model ◽  
Late Time ◽  
Total Energy Density ◽  
Self Consistent ◽  
Speed Up ◽  
Model Independent

In this work, we use cosmography to alleviate the degeneracy among cosmological models, proposing a way to parametrize matter and dark energy in terms of cosmokinematics quantities. The recipe of using cosmography allows to expand observable quantities in Taylor series and to directly compare those expansions with data. The strategy involves the expansions of [Formula: see text] and [Formula: see text], up to the second-order around [Formula: see text]. This includes additional cosmographic parameters which are fixed by current values of [Formula: see text] and [Formula: see text]. We therefore propose a fully self-consistent parametrization of the total energy density driving the late-time universe speed up. This stratagem does not remove all the degeneracy but enables one to pass from the model-dependent couple of coefficients, [Formula: see text] and [Formula: see text], to model-independent quantities determined from cosmography. Afterwards, we describe a feasible cosmographic dark energy model, in which matter is fixed whereas dark energy evolves by means of the cosmographic series. Our technique provides robust constraints on cosmokinematic parameters, permitting one to separately bound matter from dark energy densities. Our cosmographic dark energy model turns out to be one parameter only, but differently from the lambda cold dark matter ([Formula: see text]CDM) paradigm, it does not contain ansatz on the dark energy form. In addition, we even determine the free parameter of our model in suitable [Formula: see text] intervals through Monte Carlo analyses based on the Metropolis algorithm. We compare our results with the standard concordance model and we find that our treatment seems to indicate that dark energy slightly evolves in time, reducing to a pure cosmological constant only as [Formula: see text].

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.

Statefinder diagnosis for Tsallis agegraphic dark energy model with ωD − ωD′ pair

2020 ◽  
Vol 35 (06) ◽  
pp. 2050027 ◽  
Author(s):  
Shikha Srivastava ◽  
Vipin Chandra Dubey ◽  
Umesh Kumar Sharma
Keyword(s):  
Dark Energy ◽  
Dark Energy Model ◽  
Energy Model ◽  
Density Parameter ◽  
Statefinder Parameters ◽  
Agegraphic Dark Energy ◽  
New Class ◽  
Nonextensive Entropy ◽  
Age Of The Universe ◽  
The Universe

A new class of dark energy model, known as “Tsallis agegraphic dark energy (TADE),” has been proposed using the holographic principle and Tsallis nonextensive entropy (Mod. Phys. Lett. A, 2019), considering the conformal time as well as the age of the Universe as IR cutoffs in flat Universe. The trajectories for evolution of statefinder parameters in [Formula: see text], [Formula: see text], [Formula: see text] and the [Formula: see text] planes are plotted for the TADE 1 and TADE 2 models for the value of the Tsallis parameter [Formula: see text], and taking the TADE energy density parameter [Formula: see text], according to the Planck 2018 results VI — [Formula: see text]CDM observational data without interaction.

COSMOLOGICAL DYNAMICS OF DILATONIC (PHANTOM) DARK ENERGY MODEL

2006 ◽  
Vol 15 (09) ◽  
pp. 1501-1514 ◽  
Author(s):  
Z. G. HUANG ◽  
H. Q. LU
Keyword(s):  
Dark Energy ◽  
Kinetic Energy ◽  
Dark Energy Model ◽  
Energy Model ◽  
Density Parameter ◽  
Late Time ◽  
Sufficient Condition ◽  
Phantom Model ◽  
Attractor Solution ◽  
Phantom Dark Energy

In this paper, we study the cosmological dynamics of dilatonic dark energy model and its phantom model — with negative kinetic energy. When the potential is taken as the form [Formula: see text], we investigate the existence of a late time attractor solution, and find out the sufficient condition. One interesting feature found by us is that the evolutions of components of comic density are locally fluctuating on the way to the late time attractor. But this local fluctuation cannot hold the trend that the equation of state ω evolves to -1 and the cosmic density parameter Ωσ evolves to 1, which are important features for a dark energy model that can meet the current observations.

scholarly journals STATEFINDER DIAGNOSTIC FOR HOLOGRAPHIC DARK ENERGY MODEL

2005 ◽  
Vol 14 (09) ◽  
pp. 1597-1606 ◽  
Author(s):  
XIN ZHANG
Keyword(s):  
Dark Energy ◽  
Observational Data ◽  
High Precision ◽  
Significant Role ◽  
Dark Energy Model ◽  
Holographic Dark Energy ◽  
Energy Model ◽  
Holographic Dark Energy Model ◽  
Energy Models ◽  
Evolutionary Trajectories

In this paper, we study the holographic dark energy model proposed by Li from the statefinder viewpoint. We plot the evolutionary trajectories of the model with c = 1 in the statefinder parameter-planes. The statefinder diagrams characterize the properties of the holographic dark energy and show the discrimination between this scenario and other dark energy models. We also perform a statefinder diagnostic to the holographic dark energy model in cases of different c which given by three fits to observational data. The result indicates that from the statefinder viewpoint c plays a significant role in this model and should thus be determined seriously by future high precision experiments.

ATTRACTOR BEHAVIOR IN DILATONIC (PHANTOM) DARK ENERGY MODEL WITH POTENTIAL [1+(σ-A)2]e-Bσ

2006 ◽  
Vol 21 (39) ◽  
pp. 2977-2987
Author(s):  
Z. G. HUANG ◽  
H. Q. LU ◽  
W. FANG
Keyword(s):  
Dark Energy ◽  
Dark Energy Model ◽  
Energy Model ◽  
Fine Tuning ◽  
Density Parameter ◽  
Dilaton Field ◽  
Phantom Model ◽  
Attractor Solution ◽  
Phantom Dark Energy ◽  
M Theory

In this paper, we consider the dilatonic dark energy model and its phantom model. Based on the dilatonic (phantom) model, we take the potential of dilaton field of the form [1+(σ-A)2]e-Bσ which seems to connect with ideas from M-theory, and analyze the sufficient condition for the existence of attractor solution. We find that the behavior of the attractor is not sensitive to the initial condition, thus the fine-tuning problem is alleviated. By numerical analysis, we investigate the asymptotic behavior of the attractor, which corresponds to an equation of state ω = -1 and a cosmic density parameter Ωσ = 1.

scholarly journals An interacting new holographic dark energy model: Observational constraints

2019 ◽  
Vol 28 (12) ◽  
pp. 1950152 ◽  
Author(s):  
Ehsan Sadri ◽  
Martiros Khurshudyan
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Observational Data ◽  
Dark Energy Model ◽  
Holographic Dark Energy ◽  
Current Model ◽  
Energy Model ◽  
Late Time ◽  
Holographic Dark Energy Model ◽  
Frw Universe

In this paper, we study an interacting new holographic dark energy model (NHDE) in DGP braneworld with a spatially flat FRW universe. Mainly, in this study we concentrate our attention on both interacting and noninteracting forms of the model. The study shows that the equation of state and the deceleration parameter depict an accelerated universe for all variety of interactions. On the other hand, the StateFinder analysis shows that the interacting and noninteracting behave similar to both quintessence and phantom dark energy and for the present value obey the behavior of quintessence. Moreover, the result of [Formula: see text]-diagnostic emphasizes on the result of the equation of state showing that the current model in high–[Formula: see text] stays in the quintessence era and in the late time has the Phantom-like behavior. By the use of the squared sound speed [Formula: see text] we find that the present mode has a good stability. In order to obtain the best fit values of the parameters in this work, we used the latest observational data (Pantheon, Boss DR12 and Planck 2015) implementing MCMC method by the use of EMCEE python package. We also employ AkaikeInformation Criterion (AIC) and Bayesian Information Criterion (BIC) model selection tools and comparethe model with both [Formula: see text]CDM and holographic Ricci dark energy as the reference models. We observe that the evidence against the interacting and noninteracting NHDE with consideration of both references is strongly positive and BIC rules out the NHDE model. Generally, the results of AIC and BIC state that the observational data do not favor the NHDE model.

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