1. Baryonic Acoustic Oscillations
One wave around one center:
Wave starts propagating at Big Bang;
end at recombination. The final length
is the sound crossing horizon at recomb.
(Change of color means recombination.)
Many waves superimposed

2. Matter power spectrum - observations
Baryonic Acoustic Oscillations (BAO)
SDSS and 2dF galaxy surveys
from
k-space to
real space
BAO bump
gal. corr. fcn.
Narrow feature:
standard ruler
(sound crossing horizon at recombination)
comoving r (Mpc/h)
Eisenstein et al. astro-ph/
Percival et al. astro-ph/

3. Recombination affects the matter power spectrum too
sound horizon size at
recombination
Luminous SDSS red galaxies, z ~ 0.35
Wmh2=0.12,
0.13,
0.14
galaxy correlation function
Eisenstein et al. astro-ph/