Baryon acoustic oscillations in the pre-recombination universe created correlations in the matter density that can be seen today as a peak in the 2-point correlations function at the sound horizon $sim147$Mpc. This “BAO” peak, due to the same simple physics that governs CMB anisotropies, provides a standard ruler that can be used to measure cosmological distances and expansion rates and to constrain cosmological parameters. After a brief review of the physics of BAO, I will present the most recent results of the Baryon Oscillation Spectroscopy Survey (BOSS) of SDSS-3.

SPP – CEA/Saclay