Effects of a Time-Varying Color-Luminosity Parameter β on the Cosmological Constraints of Modified Gravity Models

• Published in: 理论物理通讯：英文版 2014 (12), p.927-936
• Main Author: 王爽 王永贞 张鑫
• Format: Article
• Language: English
• Subjects: dark; energy; gravity; modified; supernovae; systematic; time-varying; type; uncertainties
• ISSN: 0253-6102

It has been found that, for the Supernova Legacy Survey three-year(SNLS3) data, there is strong evidence for the redshift-evolution of color-luminosity parameter β. In previous studies, only dark energy(DE) models are used to explore the effects of a time-varying β on parameter estimation. In this paper, we extend the discussions to the case of modified gravity(MG), by considering Dvali–Gabadadze–Porrati(DGP) model, power-law type f(T) model and exponential type f(T) model. In addition to the SNLS3 data, we also use the latest Planck distance priors data,the galaxy clustering(GC) data extracted from Sloan Digital Sky Survey(SDSS) data release 7(DR7) and Baryon Oscillation Spectroscopic Survey(BOSS), as well as the direct measurement of Hubble constant H0 from the Hubble Space Telescope(HST) observation. We find that, for both cases of using the supernova(SN) data alone and using the combination of all data, adding a parameter of β can reduce χ2by ～ 36 for all the MG models, showing that a constantβ is ruled out at 6σ confidence level(CL). Moreover, we find that a time-varying β always yields a larger fractional matter density Ωm0and a smaller reduced Hubble constant h; in addition, it significantly changes the shapes of 1σ and2σ confidence regions of various MG models, and thus corrects systematic bias for the parameter estimation. These conclusions are consistent with the results of DE models, showing that β’s evolution is completely independent of the cosmological models in the background. Therefore, our work highlights the importance of considering the evolution of βin the cosmology-fits.