Observational matter power spectrum and the height of the second acoustic peak

We show that the amplitude of the second acoustic peak in the newly release d BOOMERANG-98 and MAXIMA-I data is compatible with the standard primordial nucleosynthesis and with the locally broken scale-invariant matter power s pectrum suggested by recent measurements of the power spectrum in the range 20-200 h(-1) Mpc. If the slope of matter density perturbations on large sc ales is n approximate to 1, the Hubble constant is 0.5 < h < 0.75, and rms mass fluctuations at 8 h(-1) Mpc are 0.65 less than or equal to sigma (s) l ess than or equal to 0.75, then for a universe approximately 14 Gyr old, ou r best fit within the nucleosynthesis bound Omega (B) h(2) = 0.019 +/- 0.00 24 requires 0.3 less than or equal to Omega (m) less than or equal to 0.5. Cluster abundances further constrain the matter density to be Omega (m) app roximate to 0.3. The CMB data alone are not able to determine the detailed form of the matter power spectrum in the range 0.03 < k < 0.06 h Mpc(-1), i n which deviations from the scale-invariant spectrum are expected to be mos t significant, but they do not contradict the existence of the previously c laimed peak at k similar to 0.05 h Mpc(-1) and a depression at k similar to 0.035 h Mpc(-1).