Cosmological parameters and the baryon density from CMB and galaxy fluctuations

Recent observations of the CMB fluctuations (eg Boomerang and Maxima) show an anomalously low second acoustic peak, which has been interpreted as an indication of a high primordial Big-Bang nucleosynthesis (BBN) baryon density. We reexamine the prediction by Adams et al (1997) that this would be the consequence of a 'step' in the primordial spectrum induced by a spontaneous symmetry breaking phase transition during primordial inflation. We demonstrate that a deviation from scale-invariance around k similar to 0.1h Mpc(-1) can simultaneously explain both the feature identified earlier in the APM galaxy power spectrum as well the recent CMB anisotropy data, with a baryon density consistent with the BBN value.