We use the newly released observational H(z) data (OHD), the Cosmic Microwave Background (CMB) shift parameter, and the Baryon Acoustic Oscillation (BAO) measurements data to constrain cosmological parameters of f(R) ...We use the newly released observational H(z) data (OHD), the Cosmic Microwave Background (CMB) shift parameter, and the Baryon Acoustic Oscillation (BAO) measurements data to constrain cosmological parameters of f(R) gravity in Palatini formalism in which the f(R) form is defined as f(R) = R β/Rn. Under the assumption of a spatially flat FRW universe, we get the best fitting results of the free parameters (Ωm0, n). In the calculation, we marginalize the likelihood function over H0 by integrating the probability density P ∝ e-χ2/2 to obtain the best fitting results and the confidence regions in the Ωm0-n plane. The constraints results of (Ωm0, n) = (0.33, 0.41) by OHD only and (Ωm0, n) = (0.23, 0.08) by the combination of OHD+CMB+BAO both indicate that the universe goes through three last phases, i.e., radiation dominated, matter-dominated, and late time accelerated expansion without introduction of dark energy.展开更多
We constrain cosmological parameters using only Hubble parameter data and quantify the impact of future Hubble parameter measurements on parameter estimation for the most typical dark energy models. We first constrain...We constrain cosmological parameters using only Hubble parameter data and quantify the impact of future Hubble parameter measurements on parameter estimation for the most typical dark energy models. We first constrain cosmological parameters using 52 current Hubble parameter data including the Hubble constant measurement from the Hubble Space Telescope. Then we simulate the baryon acoustic oscillation signals from WFIRST(Wide-Field Infrared Survey Telescope) covering the redshift range of z ∈ [0.5, 2] and the redshift drift data from E-ELT(European Extremely Large Telescope) in the redshift range of z ∈ [2, 5]. It is shown that solely using the current Hubble parameter data could give fairly good constraints on cosmological parameters. Compared to the current Hubble parameter data, with the WFIRST observation the H(z) constraints on dark energy would be improved slightly, while with the E-ELT observation the H(z) constraints on dark energy is enormously improved.展开更多
We explore the cosmological implications of five modified gravity(MG) models by using the recent cosmological observational data,including the recently released SNLS3 type Ia supernovae sample,the cosmic microwave bac...We explore the cosmological implications of five modified gravity(MG) models by using the recent cosmological observational data,including the recently released SNLS3 type Ia supernovae sample,the cosmic microwave background anisotropy data from the Wilkinson Microwave Anisotropy Probe 7-yr observations,the baryon acoustic oscillation results from the Sloan Digital Sky Survey data release 7,and the latest Hubble constant measurement utilizing the Wide Field Camera 3 on the Hubble Space Telescope.The MG models considered include the Dvali-Gabadadze-Porrati(DGP) model,two f(R) models,and two f(T) models.We find that compared with the ΛCDM model,MG models can not lead to an appreciable reduction of the χ 2 min.The analysis of AIC and BIC shows that the simplest cosmological constant model(ΛCDM) is still the most preferred by the current data,and the DGP model is strongly disfavored.In addition,from the observational constraints,we also reconstruct the evolutions of the growth factor in these models.We find that the current available growth factor data are not enough to distinguish these MG models from the ΛCDM model.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 10773002 and 10875012)the Scientific Research Foundation of Beijing Normal University (Grant No. 105116)
文摘We use the newly released observational H(z) data (OHD), the Cosmic Microwave Background (CMB) shift parameter, and the Baryon Acoustic Oscillation (BAO) measurements data to constrain cosmological parameters of f(R) gravity in Palatini formalism in which the f(R) form is defined as f(R) = R β/Rn. Under the assumption of a spatially flat FRW universe, we get the best fitting results of the free parameters (Ωm0, n). In the calculation, we marginalize the likelihood function over H0 by integrating the probability density P ∝ e-χ2/2 to obtain the best fitting results and the confidence regions in the Ωm0-n plane. The constraints results of (Ωm0, n) = (0.33, 0.41) by OHD only and (Ωm0, n) = (0.23, 0.08) by the combination of OHD+CMB+BAO both indicate that the universe goes through three last phases, i.e., radiation dominated, matter-dominated, and late time accelerated expansion without introduction of dark energy.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11522540,11690021,11375153,11675145the National Program for Support of Top-Notch Young Professionalsthe 2016 Program for Postdoctoral Fellowship of Zhejiang Province
文摘We constrain cosmological parameters using only Hubble parameter data and quantify the impact of future Hubble parameter measurements on parameter estimation for the most typical dark energy models. We first constrain cosmological parameters using 52 current Hubble parameter data including the Hubble constant measurement from the Hubble Space Telescope. Then we simulate the baryon acoustic oscillation signals from WFIRST(Wide-Field Infrared Survey Telescope) covering the redshift range of z ∈ [0.5, 2] and the redshift drift data from E-ELT(European Extremely Large Telescope) in the redshift range of z ∈ [2, 5]. It is shown that solely using the current Hubble parameter data could give fairly good constraints on cosmological parameters. Compared to the current Hubble parameter data, with the WFIRST observation the H(z) constraints on dark energy would be improved slightly, while with the E-ELT observation the H(z) constraints on dark energy is enormously improved.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10535060/A050207,10821504 and 10975167)the Project of Knowledge Innovation Program of Chinese Academy of Science
文摘We explore the cosmological implications of five modified gravity(MG) models by using the recent cosmological observational data,including the recently released SNLS3 type Ia supernovae sample,the cosmic microwave background anisotropy data from the Wilkinson Microwave Anisotropy Probe 7-yr observations,the baryon acoustic oscillation results from the Sloan Digital Sky Survey data release 7,and the latest Hubble constant measurement utilizing the Wide Field Camera 3 on the Hubble Space Telescope.The MG models considered include the Dvali-Gabadadze-Porrati(DGP) model,two f(R) models,and two f(T) models.We find that compared with the ΛCDM model,MG models can not lead to an appreciable reduction of the χ 2 min.The analysis of AIC and BIC shows that the simplest cosmological constant model(ΛCDM) is still the most preferred by the current data,and the DGP model is strongly disfavored.In addition,from the observational constraints,we also reconstruct the evolutions of the growth factor in these models.We find that the current available growth factor data are not enough to distinguish these MG models from the ΛCDM model.
