Test $\Lambda$CDM model with High Redshift data from Baryon Acoustic   Oscillations
  The Baryon Acoustic Oscillations (BAO) provide a standard ruler for studying cosmic expansion. The recent observations of BAO in SDSS DR9 and DR11 take measurements of $H(z)$ at several different redshifts. It is argued that the behavior of dark energy could be constrained more effectively by adding high-redshift Hubble parameter data, such as the SDSS DR11 measurement of $H(z) = 222\pm7$ km/sec/Mpc at z = 2.34. In this paper, we investigate the significance of these BAO data in the flat $\Lambda$CDM model, by combining them with the recent observational data of the Hubble constant from local distance ladder and the Cosmic Microwave Background (CMB) measurements from Planck+WP. We perform a detailed data analysis on these datasets and find that the recent observations of BAO in SDSS DR9 and DR11 have considerable tension with the Planck + WP measurements in the framework of the standard $\Lambda$CDM model. The fitting results show that the main contribution to the tension comes from the Hubble parameter measurement at redshift of $z=2.34$. But there is no visible tension once the joint data analysis by combining the datasets of SDSS and Planck+WP is performed. Thus in order to see whether dark energy does evolve, we need more independent measurements of the Hubble parameter at high redshifts. 
Yazhou Hu, Miao Li, Zhenhui Zhang
astro-ph.CO