BAO – Cosmic variance

Cosmic variance limited Baryon Acoustic Oscillations from the DEUS-FUR LCDM simulation. We investigate the non-linear evolution of Baryon Acoustic Oscillations (BAO) in the low-redshift matter Power Spectrum (PS) from the DEUS-FUR LCDM model simulation.


This is the first cosmological N-body simulation encompassing the full observable cosmic volume, thus enabling the possibility to derive cosmic variance limited predictions of the matter PS at BAO scales. We control the effect of numerical systematic errors using a series of large volume high-resolution simulations. The combined analysis allows us to measure the matter PS between z=0 and 1 to 1% over the entire BAO range, 0.03<k [h/Mpc]<0.3, in bins of size Delta k/k < 1\%. We define the BAO with respect to a non-linearly evolved smooth (wiggle-free) spectrum and determine the characteristics of the BAO peaks and dips without recurring to extrapolation from global fitting functions. We quantify the effects of non-linearities on the position and amplitude of the BAO extrema, and the coupling to the broadband slope of the PS. We compare these estimates against non-linear predictions from semi-analytical models. As an example, we show that the halo model prescription (Halofit) overestimates the amplitude of the BAO, while the regularized multi-point propagator method (RegPT), though very accurate up to k=0.15 h/Mpc, fails to account for the broadband slope at smaller scales. Quite remarkably from the analysis of the redshift evolution of BAO we find that the second dip and third peak remains unaltered by non-linear effects. Furthermore, we find that the square of the damping factor and the shift of the position of BAO extrema scale to good approximation as the square of the growth factor, in agreement with expectations from perturbation theory. This confirms the idea that an accurate measurement of BAO at different redshifts can directly probe the growth of cosmic structures.