On the effect of the degeneracy among dark energy parameters

Gong, Yungui; Gao, Qing

doi:10.1140/epjc/s10052-014-2729-2

Cited by 10 publications

(10 citation statements)

References 74 publications

(118 reference statements)

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“…This result is consistent with that in the last section obtained from GP reconstruction and ΛCDM model. To use the BAO data and constrain the matter energy density, now we consider the SSLCPL model [78,79]. This model approximates the dynamics of general thawing scalar fields over a large redshift range.…”

Section: Observational Constraints On Acceleration and Dark Energymentioning

confidence: 99%

“…In this paper, we use the GP method to reconstruct the expansion rate E(z) and the deceleration parameter q(z) from the CCH and Pantheon+MCT data. To probe the property of cosmic acceleration and dark energy with the combination of different observational data, we parameterize the deceleration parameter q(z) with a simple two-parameter model q(z) = 1/2 + (q 1 z + q 2 )/(1 + z) 2 [76,77] and the equation of state parameter w(z) with the SSLCPL model [78,79] which approximates the dynamics of general thawing scalar fields over a large redshift range.…”

Section: Introductionmentioning

confidence: 99%

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The evidence of cosmic acceleration and observational constraints

Yang,

Gong

2019

Preprint

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Directly comparing the 6 expansion rates measured by type Ia supernovae data and the lower bound on the expansion rate set by the strong energy conditions or the null hypothesis that there never exists cosmic acceleration, we see 3σ direct evidence of cosmic acceleration and the Rh = ct model is strongly excluded by the type Ia supernovae data. We also use Gaussian process method to reconstruct the expansion rate and the deceleration parameter from the 31 cosmic chronometers data and the 6 data points on the expansion rate measured from type Ia supernoave data, the direct evidence of cosmic acceleration is more than 3σ and we find that the transition redshift z t = 0.60 +0.21 −0.12 at which the expansion of the Universe underwent the transition from acceleration to deceleration. The Hubble constant inferred from the cosmic chronometers data with the Gaussian process method is H 0 = 67.46 ± 4.75 Km/s/Mpc. By fitting two different two-parameter models to the observational data, we find that the constraints on the model parameters from either the full distance modulus data by the Pantheon compilation or the compressed expansion rate data are very similar, and the derived Hubble constants are consistent with the Planck 2018 result. Our results confirm that the 6 compressed expansion rate data can replace the full 1048 distance modulus data from the Pantheon compilation. We derive the transition redshift z t = 0.61 +0.24 −0.16 by fitting a simple q(z) model to the combination of cosmic chronometers data and the Pantheon compilation, the result is consistent with that obtained from the reconstruction with Gaussian process.

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Section: Observational Constraints On Acceleration and Dark Energymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The evidence of cosmic acceleration and observational constraints

Yang,

Gong

2019

Preprint

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“…To explain the cosmic acceleration, an exotic energy component called dark energy with negative pressure was proposed (Riess et al 1998;Perlmutter et al 1999;Astier et al 2006;Hicken et al 2009;Amanullah et al 2010;Spergel et al 2003Spergel et al , 2007Komatsu et al 2009Komatsu et al , 2011Tegmark et al 2004;Eisenstein et al 2005;Cao et al 2011Cao et al , 2012aGao & Gong 2014;Gong et al 2013Gong et al , 2014. The most simple candidate for dark energy is the vacuum energy known as the cosmological constant Λ.…”

Section: Discussionmentioning

confidence: 99%

“…We adopt the Markov Chain Monte Carlo (MCMC) technique to constrain LIV and model parameters with the observational data. In order to derive tighter constraints on the model parameters, we combine the time delay data from GRBs with the cosmic microwave background (CMB) data from the Planck first year release (Ade et al 2014;Wang et al 2013), the baryon acoustic oscillation (BAO) data (Blake et al 2011;Beutler et al 2011;Gong et al 2014;Percival et al 2010), and the 557 Union2 SNeIa data (Amanullah et al 2010). This paper is organized as follows: we introduce the LIV in section II.…”

Section: Introductionmentioning

confidence: 99%

Constraints on the Lorentz Invariance Violation With Gamma-Ray Bursts via a Markov Chain Monte Carlo Approach

Pan

Gong

Cao

et al. 2015

ApJ

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In quantum theory of gravity, we expect the Lorentz Invariance Violation (LIV) and the modification of the dispersion relation between energy and momentum for photons. The effect of the energydependent velocity due to the modified dispersion relation for photons was studied in the standard cosmological context by using a sample of Gamma Ray Bursts (GRBs). In this paper we mainly discuss the possible LIV effect by using different cosmological models for the accelerating universe. Due to the degeneracies among model parameters, the GRBs' time delay data are combined with the cosmic microwave background data from the Planck first year release, the baryon acoustic oscillation data at six different redshifts, as well as Union2 type Ia supernovae data, to constrain both the model parameters and the LIV effect. We find no evidence of LIV.

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“…In particular, the tracker field φ tracks below the background density for most of the history of the Universe until it starts to dominate recently for a wide range of initial conditions, and there exists a relation between w φ and the fractional energy density Ω φ = 8πGρ φ /(3H 2 ) today, where the Hubble parameter H(t) =ȧ/a. There also exists a general w φ − Ω φ relation for the thawing solutions which is well approximated by some analytical expressions [37][38][39][40][41][42][43][44][45][46][47]. In this Letter, we will discuss the general dynamics such as the w φ − Ω φ relation and the bound on w ′ φ = dw φ /d ln a of the tracking and thawing fields.…”

Section: Introductionmentioning

confidence: 99%

The general property of dynamical quintessence field

Gong

2014

Physics Letters B

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We discuss the general dynamical behaviors of quintessence field, in particular, the general conditions for tracking and thawing solutions are discussed. We explain what the tracking solutions mean and in what sense the results depend on the initial conditions. Based on the definition of tracking solution, we give a simple explanation on the existence of a general relation between $w_\phi$ and $\Omega_\phi$ which is independent of the initial conditions for the tracking solution. A more general tracker theorem which requires large initial values of the roll parameter is then proposed. To get thawing solutions, the initial value of the roll parameter needs to be small. The power-law and pseudo-Nambu Goldstone boson potentials are used to discuss the tracking and thawing solutions. A more general $w_\phi-\Omega_\phi$ relation is derived for the thawing solutions. Based on the asymptotical behavior of the $w_\phi-\Omega_\phi$ relation, the flow parameter is used to give an upper limit on $w_\phi'$ for the thawing solutions. If we use the observational constraint $w_{\phi 0}<-0.8$ and $0.2<\Omega_{m0}<0.4$, then we require $n\lesssim 1$ for the inverse power-law potential $V(\phi)=V_0(\phi/m_{pl})^{-n}$ with tracking solutions and the initial value of the roll parameter $|\lambda_i|<1.3$ for the potentials with the thawing solutions.Comment: 11 figures, corrected some typos and presentation improved, PLB in pres

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On the effect of the degeneracy among dark energy parameters

Cited by 10 publications

References 74 publications

The evidence of cosmic acceleration and observational constraints

The evidence of cosmic acceleration and observational constraints

Constraints on the Lorentz Invariance Violation With Gamma-Ray Bursts via a Markov Chain Monte Carlo Approach

The general property of dynamical quintessence field

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