Beating non-linearities: improving the baryon acoustic oscillations with the linear point

We propose a new way of looking at the Baryon Acoustic Oscillation in the large-scale-structure clustering correlation function. We identify a scale s_LP that has two fundamental features: its position is insensitive to non-linear gravity, redshift-space distortions and scale-dependent bias at the 0.5 per cent level; it is geometrical, I.e. independent of the power spectrum of the primordial density fluctuation parameters. These two properties together make s_LP, called the `linear point', an excellent cosmological standard ruler. The linear point is also appealing because it is easily identified irrespectively of how non-linearities distort the correlation function. Finally, the correlation function amplitude at s_LP is similarly insensitive to non-linear corrections to within a few per cent. Hence, exploiting the particular baryon features in the correlation function, we propose three new estimators for growth measurements. A preliminary analysis of s_LP in current data is encouraging.