BAO Physics
Sound speed in plasma:
c_s = c/√3 × 1/√(1+R)
R = 3ρ_b/4ρ_γ
Sound horizon at recomb.:
r_s ≈ 147 Mpc
BAO peak: -
Sound horizon: -
After recombination
(z≈1100), photons free-
stream but baryons are
frozen — BAO imprinted
in galaxy clustering
Sound speed in plasma:
c_s = c/√3 × 1/√(1+R)
R = 3ρ_b/4ρ_γ
Sound horizon at recomb.:
r_s ≈ 147 Mpc
BAO peak: -
Sound horizon: -
After recombination
(z≈1100), photons free-
stream but baryons are
frozen — BAO imprinted
in galaxy clustering