The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Bharat Ratra - One of the best experts on this subject based on the ideXlab platform.
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using pantheon and des supernova baryon acoustic oscillation and Hubble Parameter data to constrain the Hubble constant dark energy dynamics and spatial curvature
Monthly Notices of the Royal Astronomical Society, 2021Co-Authors: Shu-lei Cao, Joseph V Ryan, Bharat RatraAbstract:We use Pantheon Type Ia supernova (SN Ia) apparent magnitude, DES-3yr binned SN Ia apparent magnitude, Hubble Parameter, and baryon acoustic oscillation measurements to constrain six spatially flat and non-flat cosmological models. These sets of data provide mutually consistent cosmological constraints in the six cosmological models we study. A joint analysis of these data sets provides model-independent estimates of the Hubble constant, $H_0=68.8\pm1.8\ \rm{km \ s^{-1} \ Mpc^{-1}}$, and the non-relativistic matter density Parameter, $\Omega_{\rm m_0}=0.294\pm0.020$. Although the joint constraints prefer mild dark energy dynamics and a little spatial curvature, they do not rule out dark energy being a cosmological constant and flat spatial hypersurfaces. We also add quasar angular size and H II starburst galaxy measurements to the combined data set and find more restrictive constraints.
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Quasar X-ray and UV flux, baryon acoustic oscillation, and Hubble Parameter measurement constraints on cosmological model Parameters
Monthly Notices of the Royal Astronomical Society, 2020Co-Authors: Narayan Khadka, Bharat RatraAbstract:We use the Risaliti & Lusso (2015) compilation of 808 X-ray and UV flux measurements of quasars (QSOs) in the redshift range $0.061 \leq z \leq 6.28$, alone and in conjuction with baryon acoustic oscillation (BAO) and Hubble Parameter [$H(z)$] measurements, to constrain cosmological Parameters in six cosmological models. The QSO data constraints are significantly weaker than, but consistent with, those from the $H(z)$ + BAO data. A joint analysis of the QSO + $H(z)$ + BAO data is consistent with the current standard model, spatially-flat $\Lambda$CDM, but mildly favors closed spatial hypersurfaces and dynamical dark energy.
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baryon acoustic oscillation Hubble Parameter and angular size measurement constraints on the Hubble constant dark energy dynamics and spatial curvature
Monthly Notices of the Royal Astronomical Society, 2019Co-Authors: Joseph V Ryan, Y. Q. Chen, Bharat RatraAbstract:In this paper we use all available baryon acoustic oscillation, Hubble Parameter, and quasar angular size data to constrain six dark energy cosmological models, both spatially flat and non-flat. Depending on the model and data combination considered, these data mildly favor closed spatial hypersurfaces (by as much as $1.7\sigma$) and dark energy dynamics (up to a little over $2\sigma$) over a cosmological constant $\Lambda$. The data also favor, at $1.8\sigma$ to $3.4\sigma$, depending on the model and data combination, a lower Hubble constant than what is measured from the local expansion rate.
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measuring the Hubble constant and spatial curvature from supernova apparent magnitude baryon acoustic oscillation and Hubble Parameter data
Astrophysics and Space Science, 2019Co-Authors: Changyung Park, Bharat RatraAbstract:Cosmic microwave background (CMB) anisotropy (spatial inhomogeneity) data provide the tightest constraints on the Hubble constant, matter density, spatial curvature, and dark energy dynamics. Other data, sensitive to the evolution of only the spatially homogeneous part of the cosmological model, such as Type Ia supernova apparent magnitude, baryon acoustic oscillation distance, and Hubble Parameter measurements, can be used in conjunction with the CMB data to more tightly constrain Parameters. Recent joint analyses of CMB and such non-CMB data indicate that slightly closed spatial hypersurfaces are favored in nonflat untilted inflation models and that dark energy dynamics cannot be ruled out, and favor a smaller Hubble constant. We show that the constraints that follow from these non-CMB data alone are consistent with those that follow from the CMB data alone and so also consistent with, but weaker than, those that follow from the joint analyses of the CMB and non-CMB data.
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Constraints on dark energy dynamics and spatial curvature from Hubble Parameter and baryon acoustic oscillation data
Monthly Notices of the Royal Astronomical Society, 2018Co-Authors: Joseph Ryan, Sanket Doshi, Bharat RatraAbstract:We use all available baryon acoustic oscillation distance measurements and Hubble Parameter data to constrain the cosmological constant $\Lambda$, dynamical dark energy, and spatial curvature in simple cosmological models. We find that the consensus spatially flat $\Lambda$CDM model provides a reasonable fit to the data, but depending on the Hubble constant prior and cosmological model, it can be a little more than 1$\sigma$ away from the best-fit model, which can favor mild dark energy dynamics or non-flat spatial hypersurfaces.
Tong-jie Zhang - One of the best experts on this subject based on the ideXlab platform.
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cosmological constraints on the coupling model from observational Hubble Parameter and baryon acoustic oscillation measurements
arXiv: Cosmology and Nongalactic Astrophysics, 2021Co-Authors: Shu-lei Cao, Tong-jie Zhang, Xinya Wang, Tingting ZhangAbstract:In the paper, we consider two models in which dark energy is coupled with either dust matter or dark matter, and discuss the conditions that allow more time for structure formation to take place at high redshifts. These models are expected to have a larger age of the universe than that of $\Lambda$CDM [universe consists of cold dark matter (CDM) and dark energy (a cosmological constant, $\Lambda$)], so it can explain the formation of high redshift gravitationally bound systems which the $\Lambda$CDM model cannot interpret. We use the observational Hubble Parameter data (OHD) and Hubble Parameter obtained from cosmic chronometers method ($H(z)$) in combination with baryon acoustic oscillation (BAO) data to constrain these models. With the best-fitting Parameters, we discuss how the age, the deceleration Parameter, and the energy density Parameters evolve in the new universes, and compare them with that of $\Lambda$CDM.
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the constraint ability of Hubble Parameter by gravitational wave standard sirens on cosmological Parameters
arXiv: Cosmology and Nongalactic Astrophysics, 2019Co-Authors: Tong-jie Zhang, Zhi-e Liu, Hao-yi Wan, Y Liu, Tingting Zhang, Baoquan WangAbstract:In this paper, we present the application of a new method measuring Hubble Parameter $H(z)$ by using the anisotropy of luminosity distance($d_{L}$) of the gravitational wave(GW) standard sirens of neutron star(NS) binary system. The method has never been put into practice so far due to the lack of the ability of detecting GW. However, LIGO's success in detecting GW of black hole(BH) binary system merger announced the potential possibility of this new method. We apply this method to several GW detecting projects, including Advanced LIGO(aLIGO), Einstein Telescope(ET) and DECIGO, and evaluate its constraint ability on cosmological Parameters of $H(z)$. It turns out that the $H(z)$ by aLIGO and ET is of bad accuracy, while the $H(z)$ by DECIGO shows a good one. We simulate $H(z)$ data at every 0.1 redshift span using the error information of $H(z)$ by DECIGO, and put the mock data into the forecasting of cosmological Parameters. Compared with the previous data and method, we get an obviously tighter constraint on cosmological Parameters by mock data, and a concomitantly higher value of Figure of Merit(FoM, the reciprocal of the area enclosed by the $2\sigma$ confidence region). For a 3-year-observation by standard sirens of DECIGO, the FoM value is as high as 170.82. If a 10-year-observation is launched, the FoM could reach 569.42. For comparison, the FoM of 38 actual observed $H(z)$ data(OHD) is 9.3. We also investigate the undulant universe, which shows a comparable improvement on the constraint of cosmological Parameters. These improvement indicates that the new method has great potential in further cosmological constraints.
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cosmological model independent test of varlambda cdm with two point diagnostic by the observational Hubble Parameter data
European Physical Journal C, 2018Co-Authors: Shu-lei Cao, Xiao-wei Duan, Xiao-lei Meng, Tong-jie ZhangAbstract:Aiming at exploring the nature of dark energy (DE), we use forty-three observational Hubble Parameter data (OHD) in the redshift range $$0 < z \leqslant 2.36$$ to make a cosmological model-independent test of the $$\varLambda $$ CDM model with two-point $$Omh^2(z_{2};z_{1})$$ diagnostic. In $$\varLambda $$ CDM model, with equation of state (EoS) $$w=-1$$ , two-point diagnostic relation $$Omh^2 \equiv \varOmega _{\mathrm{m}}h^2$$ is tenable, where $$\varOmega _{\mathrm{m}}$$ is the present matter density Parameter, and h is the Hubble Parameter divided by 100 $${\mathrm {km\, s^{-1} \ Mpc^{-1}}}$$ . We utilize two methods: the weighted mean and median statistics to bin the OHD to increase the signal-to-noise ratio of the measurements. The binning methods turn out to be promising and considered to be robust. By applying the two-point diagnostic to the binned data, we find that although the best-fit values of $$Omh^2$$ fluctuate as the continuous redshift intervals change, on average, they are continuous with being constant within 1 $$\sigma $$ confidence interval. Therefore, we conclude that the $$\varLambda $$ CDM model cannot be ruled out.
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Testing backreaction effects with observational Hubble Parameter data
The European Physical Journal C, 2018Co-Authors: Shu-lei Cao, Hao-yi Wan, Huan-yu Teng, Tong-jie ZhangAbstract:In order to explore the generic properties of a backreaction model for explaining the accelerated expansion of the Universe, we exploit two metrics to describe the late time Universe. Since the standard FLRW metric cannot precisely describe the late time Universe on small scales, the template metric with an evolving curvature Parameter $\kappa_{\mathcal{D}}(t)$ is employed. However, we doubt the validity of the prescription for $\kappa_{\mathcal{D}}$, which motivates us apply observational Hubble Parameter data (OHD) to constrain Parameters in dust cosmology. First, for FLRW metric, by getting best-fit constraints of $\Omega^{\mathcal{D}_0}_m = 0.25^{+0.03}_{-0.03}$, $n = 0.02^{+0.69}_{-0.66}$, and $H_{\mathcal{D}_0} = 70.54^{+4.24}_{-3.97}\ {\rm km \ s^{-1} \ Mpc^{-1}}$, the evolutions of Parameters are explored. Second, in template metric context, by marginalizing over $H_{\mathcal{D}_0}$ as a prior of uniform distribution, we obtain the best-fit values of $n=-1.22^{+0.68}_{-0.41}$ and ${{\Omega}_{m}^{\mathcal{D}_{0}}}=0.12^{+0.04}_{-0.02}$. Moreover, we utilize three different Gaussian priors of $H_{\mathcal{D}_0}$, which result in different best-fits of $n$, but almost the same best-fit value of ${{\Omega}_{m}^{\mathcal{D}_{0}}}\sim0.12$. Also, the absolute constraints without marginalization of Parameter are obtained: $n=-1.1^{+0.58}_{-0.50}$ and ${{\Omega}_{m}^{\mathcal{D}_{0}}}=0.13\pm0.03$. With these constraints, the evolutions of the effective deceleration Parameter $q^{\mathcal{D}}$ indicate that the backreaction can account for the accelerated expansion of the Universe without involving extra dark energy component in the scaling solution context. Nevertheless, the results also verify that the prescription of $\kappa_{\mathcal{D}}$ is insufficient and should be improved.
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testing backreaction effects with observational Hubble Parameter data
European Physical Journal C, 2018Co-Authors: Shu-lei Cao, Hao-yi Wan, Huan-yu Teng, Tong-jie ZhangAbstract:The spatially averaged inhomogeneous Universe includes a kinematical backreaction term $${\mathcal {Q}}_{\mathcal {D}}$$ that is relate to the averaged spatial Ricci scalar $${\langle \mathcal {R}} \rangle _{\mathcal {D}}$$ in the framework of general relativity. Under the assumption that $${\mathcal {Q}}_{\mathcal {D}}$$ and $${\langle \mathcal {R}} \rangle _{\mathcal {D}}$$ obey the scaling laws of the volume scale factor $$a_{\mathcal {D}}$$ , a direct coupling between them with a scaling index n is remarkable. In order to explore the generic properties of a backreaction model for explaining the accelerated expansion of the Universe, we exploit two metrics to describe the late time Universe. Since the standard FLRW metric cannot precisely describe the late time Universe on small scales, the template metric with an evolving curvature Parameter $$\kappa _{\mathcal {D}}(t)$$ is employed. However, we doubt the validity of the prescription for $$\kappa _{\mathcal {D}}$$ , which motivates us apply observational Hubble Parameter data (OHD) to constrain Parameters in dust cosmology. First, for FLRW metric, by getting best-fit constraints of $$\varOmega ^{{\mathcal {D}}_0}_m = 0.25^{+0.03}_{-0.03}$$ , $$n = 0.02^{+0.69}_{-0.66}$$ , and $$H_{\mathcal {D}_0} = 70.54^{+4.24}_{-3.97}\ \mathrm{km \ s^{-1} \ Mpc^{-1}}$$ , the evolutions of Parameters are explored. Second, in template metric context, by marginalizing over $$H_{\mathcal {D}_0}$$ as a prior of uniform distribution, we obtain the best-fit values of $$n=-1.22^{+0.68}_{-0.41}$$ and $${{\varOmega }_{m}^{\mathcal {D}_{0}}}=0.12^{+0.04}_{-0.02}$$ . Moreover, we utilize three different Gaussian priors of $$H_{\mathcal {D}_0}$$ , which result in different best-fits of n, but almost the same best-fit value of $${{\varOmega }_{m}^{\mathcal {D}_{0}}}\sim 0.12$$ . Also, the absolute constraints without marginalization of Parameter are obtained: $$n=-1.1^{+0.58}_{-0.50}$$ and $${{\varOmega }_{m}^{\mathcal {D}_{0}}}=0.13\pm 0.03$$ . With these constraints, the evolutions of the effective deceleration Parameter $$q^{\mathcal {D}}$$ indicate that the backreaction can account for the accelerated expansion of the Universe without involving extra dark energy component in the scaling solution context. Nevertheless, the results also verify that the prescription of $$\kappa _{\mathcal {D}}$$ is insufficient and should be improved.
Omer Farooq - One of the best experts on this subject based on the ideXlab platform.
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Hubble Parameter measurement constraints on the redshift of the deceleration acceleration transition dynamical dark energy and space curvature
The Astrophysical Journal, 2017Co-Authors: Omer Farooq, Foram Ranjeet Madiyar, Sara Crandall, Foram Ranjeet Madiyar, Sara Crandall, Bharat RatraAbstract:Citation: Farooq, O., Madiyar, F. R., Crandall, S., & Ratra, B. (2017). Hubble Parameter MEASUREMENT CONSTRAINTS ON THE REDSHIFT OF THE DECELERATION-ACCELERATION TRANSITION, DYNAMICAL DARK ENERGY, AND SPACE CURVATURE. Astrophysical Journal, 835(1), 11. doi:10.3847/1538-4357/835/1/26
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Hubble Parameter measurement constraints on the redshift of the deceleration acceleration transition dynamical dark energy and space curvature
arXiv: Cosmology and Nongalactic Astrophysics, 2016Co-Authors: Omer Farooq, Foram Ranjeet Madiyar, Sara Crandall, Bharat RatraAbstract:We compile an updated list of 38 measurements of the Hubble Parameter $H(z)$ between redshifts $0.07 \leq z \leq 2.36$ and use them to place constraints on model Parameters of constant and time-varying dark energy cosmological models, both spatially flat and curved. We use five models to measure the redshift of the cosmological deceleration-acceleration transition, $z_{\rm da}$, from these $H(z)$ data. Within the error bars, the measured $z_{\rm da}$ are insensitive to the model used, depending only on the value assumed for the Hubble constant $H_0$. The weighted mean of our measurements is $z_{\rm da} = 0.72 \pm 0.05\ (0.84 \pm 0.03)$ for $H_0 = 68 \pm 2.8\ (73.24 \pm 1.74)$ km s$^{-1}$ Mpc$^{-1}$ and should provide a reasonably model-independent estimate of this cosmological Parameter. The $H(z)$ data are consistent with the standard spatially-flat $\Lambda$CDM cosmological model but do not rule out non-flat models or dynamical dark energy models.
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binned Hubble Parameter measurements and the cosmological deceleration acceleration transition
Physics Letters B, 2013Co-Authors: Sara Crandall, Omer Farooq, Bharat RatraAbstract:Abstract Weighted mean and median statistics techniques are used to combine 23 independent lower redshift, z 1.04 , Hubble Parameter, H ( z ) , measurements and determine binned forms of H ( z ) . When these are combined with 5 higher redshift, 1.3 ≤ z ≤ 2.3 , H ( z ) measurements the resulting constraints on cosmological Parameters, of three cosmological models, that follow from the weighted-mean binned data are almost identical to those derived from analyses using the 28 independent H ( z ) measurements. This is consistent with what is expected if the lower redshift measurements errors are Gaussian. Plots of the binned weighted-mean H ( z ) / ( 1 + z ) versus z data are consistent with the presence of a cosmological deceleration–acceleration transition at redshift z da = 0.74 ± 0.05 [30] , which is expected in cosmological models with present-epoch energy budget dominated by dark energy as in the standard spatially-flat Λ CDM cosmological model.
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constraints on dark energy from the lyα forest baryon acoustic oscillations measurement of the redshift 2 3 Hubble Parameter
Physics Letters B, 2013Co-Authors: Omer Farooq, Bharat RatraAbstract:Abstract We use the Busca et al. (2012) [11] measurement of the Hubble Parameter at redshift z = 2.3 in conjunction with 21 lower z measurements, from Simon, Verde, and Jimenez (2005) [81] , Gaztanaga, Cabre, and Hui (2009) [33] , Stern et al. (2010) [85] , and Moresco et al. (2012) [52] , to place constraints on model Parameters of constant and time-evolving dark energy cosmological models. The inclusion of the new Busca et al. (2012) [11] measurement results in H ( z ) constraints significantly more restrictive than those derived by Farooq, Mania, and Ratra (2013) [31] . These H ( z ) constraints are now more restrictive than those that follow from current Type Ia supernova (SNIa) apparent magnitude measurements Suzuki et al. (2012) [86] . The H ( z ) constraints by themselves require an accelerating cosmological expansion at about 2 σ confidence level, depending on cosmological model and Hubble constant prior used in the analysis. A joint analysis of H ( z ) , baryon acoustic oscillation peak length scale, and SNIa data favors a spatially-flat cosmological model currently dominated by a time-independent cosmological constant but does not exclude slowly-evolving dark energy density.
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Hubble Parameter measurement constraints on the cosmological deceleration acceleration transition redshift
The Astrophysical Journal, 2013Co-Authors: Omer Farooq, Bharat RatraAbstract:We compile a list of 28 independent measurements of the Hubble Parameter between redshifts 0.07 ≤ z ≤ 2.3 and use this to place constraints on model Parameters of constant and time-evolving dark energy cosmologies. These H(z) measurements by themselves require a currently accelerating cosmological expansion at about, or better than, 3σ confidence. The mean and standard deviation of the six best-fit model deceleration-acceleration transition redshifts (for the three cosmological models and two Hubble constant priors we consider) are z da = 0.74 ± 0.05, in good agreement with the recent Busca et al. determination of z da = 0.82 ± 0.08 based on 11 H(z) measurements between redshifts 0.2 ≤ z ≤ 2.3, almost entirely from baryon-acoustic-oscillation-like data.
Zong-hong Zhu - One of the best experts on this subject based on the ideXlab platform.
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constraints on the exponential f r model from latest Hubble Parameter measurements
Physical Review D, 2015Co-Authors: Yun Chen, C Q Geng, Chung-chi Lee, Ling-wei Luo, Zong-hong ZhuAbstract:We investigate the viable exponential $f(R)$ gravity in the metric formalism with $f(R)=-\beta R_s (1-e^{-R/R_s})$. The latest sample of the Hubble Parameter measurements with 23 data points is used to place bounds on this $f(R)$ model. A joint analysis is also performed with the luminosity distances of Type Ia supernovae and baryon acoustic oscillations in the clustering of galaxies, and the shift Parameters from the cosmic microwave background measurements, which leads to $0.240 1.47$ at 1$\sigma$ confidence level. The evolutions of the deceleration Parameter $q(z)$ and the effective equations of state $\omega_{de}^{eff}(z)$ and $\omega_{tot}^{eff}(z)$ are displayed. By taking the best-fit Parameters as prior values, we work out the transition redshift (deceleration/acceleration) $z_T$ to be about 0.77. It turns out that the recent observations are still unable to distinguish the background dynamics in the $\Lambda$CDM and exponential $f(R)$ models.
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constraints on a phicdm model from strong gravitational lensing and updated Hubble Parameter measurements
Journal of Cosmology and Astroparticle Physics, 2015Co-Authors: Yun Chen, C Q Geng, Shuo Cao, Yumei Huang, Zong-hong ZhuAbstract:We constrain the scalar field dark energy model with an inverse power-law potential, i.e., V() −α (α > 0), from a set of recent cosmological observations by compiling an updated sample of Hubble Parameter measurements including 30 independent data points. Our results show that the constraining power of the updated sample of H(z) data with the HST prior on H0 is stronger than those of the SCP Union2 and Union2.1 compilations. A recent sample of strong gravitational lensing systems is also adopted to confine the model even though the results are not significant. A joint analysis of the strong gravitational lensing data with the more restrictive updated Hubble Parameter measurements and the Type Ia supernovae data from SCP Union2 indicates that the recent observations still can not distinguish whether dark energy is a time-independent cosmological constant or a time-varying dynamical component.
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constraints on a phi cdm model from strong gravitational lensing and updated Hubble Parameter measurements
arXiv: Cosmology and Nongalactic Astrophysics, 2013Co-Authors: Y. Q. Chen, C Q Geng, Shuo Cao, Yumei Huang, C Q Geng, Zong-hong ZhuAbstract:We constrain the scalar field dark energy model with an inverse power-law potential, i.e., $V(\phi)\propto {\phi}^{-\alpha}$ ($\alpha>0$), from a set of recent cosmological observations by compiling an updated sample of Hubble Parameter measurements including 30 independent data points. Our results show that the constraining power of the updated sample of $H(z)$ data with the HST prior on $H_0$ is stronger than those of the SCP Union2 and Union2.1 compilations. A recent sample of strong gravitational lensing systems is also adopted to confine the model even though the results are not significant. A joint analysis of the strong gravitational lensing data with the more restrictive updated Hubble Parameter measurements and the Type Ia supernovae data from SCP Union2 indicates that the recent observations still can not distinguish whether dark energy is a time-independent cosmological constant or a time-varying dynamical component.
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Testing cosmic opacity from SNe Ia and Hubble Parameter through three cosmological-model-independent methods
Physics Letters B, 2013Co-Authors: Kai Liao, Jing Ming, Zong-hong ZhuAbstract:AbstractWe use the newly published 28 observational Hubble Parameter data (H(z)) and current largest SNe Ia samples (Union2.1) to test whether the universe is transparent. Three cosmological-model-independent methods (nearby SNe Ia method, interpolation method and smoothing method) are proposed through comparing opacity-free distance modulus from Hubble Parameter data and opacity-dependent distance modulus from SNe Ia. Two Parameterizations, τ(z)=2ϵz and τ(z)=(1+z)2ϵ−1 are adopted for the optical depth associated to the cosmic absorption. We find that the results are not sensitive to the methods and Parameterizations. Our results support a transparent universe
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observational constraints on unified dark matter including Hubble Parameter data
Physics Letters B, 2012Co-Authors: Kai Liao, Shuo Cao, Jun Wang, Xiaolong Gong, Zong-hong ZhuAbstract:Abstract We constrain a unified dark matter (UDM) model from the latest observational data. This model assumes that the dark sector is degenerate. Dark energy and dark matter are the same component. It can be described by an affine equation of state P X = p 0 + α ρ X . Our data set contains the newly revised H ( z ) data, type Ia supernovae (SNe Ia) from Union2 set, baryonic acoustic oscillation (BAO) observation from the spectroscopic Sloan Digital Sky Survey (SDSS) data release 7 (DR7) galaxy sample, as well as the cosmic microwave background (CMB) observation from the 7-year Wilkinson Microwave Anisotropy Probe (WMAP7) results. By using the Markov Chain Monte Carlo (MCMC) method, we obtain the results in a flat universe: Ω Λ = 0.719 − 0.0305 + 0.0264 ( 1 σ ) − 0.0458 + 0.0380 ( 2 σ ) , α = 1.72 − 4.79 + 3.92 ( 1 σ ) − 7.30 + 5.47 ( 2 σ ) ( × 10 − 3 ) , Ω b h 2 = 0.0226 − 0.0011 + 0.0011 ( 1 σ ) − 0.0015 + 0.0016 ( 2 σ ) . Moreover, when considering a non-flat universe, Ω Λ = 0.722 − 0.0447 + 0.0362 ( 1 σ ) − 0.0634 + 0.0479 ( 2 σ ) , α = 0.242 − 0.775 + 0.787 ( 1 σ ) − 1.03 + 1.10 ( 2 σ ) ( × 10 − 2 ) , Ω b h 2 = 0.0227 − 0.0014 + 0.0015 ( 1 σ ) − 0.0018 + 0.0021 ( 2 σ ) , Ω k = − 0.194 − 1.85 + 2.02 ( 1 σ ) − 2.57 + 2.75 ( 2 σ ) ( × 10 − 2 ) . These give a more stringent results than before. We also give the results from other combinations of these data for comparison. The observational Hubble Parameter data can give a more stringent constraint than SNe Ia. From the constraint results, we can see the Parameters α and Ω k are very close to zero, which means a flat universe is strongly supported and the speed of sound of the dark sector seems to be zero.
Yun Chen - One of the best experts on this subject based on the ideXlab platform.
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constraints on the exponential f r model from latest Hubble Parameter measurements
Physical Review D, 2015Co-Authors: Yun Chen, C Q Geng, Chung-chi Lee, Ling-wei Luo, Zong-hong ZhuAbstract:We investigate the viable exponential $f(R)$ gravity in the metric formalism with $f(R)=-\beta R_s (1-e^{-R/R_s})$. The latest sample of the Hubble Parameter measurements with 23 data points is used to place bounds on this $f(R)$ model. A joint analysis is also performed with the luminosity distances of Type Ia supernovae and baryon acoustic oscillations in the clustering of galaxies, and the shift Parameters from the cosmic microwave background measurements, which leads to $0.240 1.47$ at 1$\sigma$ confidence level. The evolutions of the deceleration Parameter $q(z)$ and the effective equations of state $\omega_{de}^{eff}(z)$ and $\omega_{tot}^{eff}(z)$ are displayed. By taking the best-fit Parameters as prior values, we work out the transition redshift (deceleration/acceleration) $z_T$ to be about 0.77. It turns out that the recent observations are still unable to distinguish the background dynamics in the $\Lambda$CDM and exponential $f(R)$ models.
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constraints on a phicdm model from strong gravitational lensing and updated Hubble Parameter measurements
Journal of Cosmology and Astroparticle Physics, 2015Co-Authors: Yun Chen, C Q Geng, Shuo Cao, Yumei Huang, Zong-hong ZhuAbstract:We constrain the scalar field dark energy model with an inverse power-law potential, i.e., V() −α (α > 0), from a set of recent cosmological observations by compiling an updated sample of Hubble Parameter measurements including 30 independent data points. Our results show that the constraining power of the updated sample of H(z) data with the HST prior on H0 is stronger than those of the SCP Union2 and Union2.1 compilations. A recent sample of strong gravitational lensing systems is also adopted to confine the model even though the results are not significant. A joint analysis of the strong gravitational lensing data with the more restrictive updated Hubble Parameter measurements and the Type Ia supernovae data from SCP Union2 indicates that the recent observations still can not distinguish whether dark energy is a time-independent cosmological constant or a time-varying dynamical component.
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Hubble Parameter data constraints on dark energy
Physics Letters B, 2011Co-Authors: Yun Chen, Bharat RatraAbstract:Abstract We use Hubble Parameter versus redshift data from Stern et al. (2010) [1] and Gaztanaga et al. (2009) [2] to place constraints on model Parameters of constant and time-evolving dark energy cosmological models. These constraints are consistent with (through not as restrictive as) those derived from supernova Type Ia magnitude-redshift data. However, they are more restrictive than those derived from galaxy cluster angular diameter distance, and comparable with those from gamma-ray burst and lookback time data. A joint analysis of the Hubble Parameter data with more restrictive baryon acoustic oscillation peak length scale and supernova Type Ia apparent magnitude data favors a spatially-flat cosmological model currently dominated by a time-independent cosmological constant but does not exclude time-varying dark energy.