On the APM power spectrum and the CMB anisotropy: evidence for a phase transition during inflation?

Adams et al. have noted that according to our current understanding of the unification of fundamental interactions, there should have been phase trans itions associated with spontaneous symmetry breaking during the inflationar y era. This may have resulted in the breaking of scale-invariance of the pr imordial density perturbation for brief periods. A possible such feature wa s identified in the power spectrum of galaxy clustering in the automated pl ate measurement (APM) survey at the scale k similar to 0.1 h Mpc (- 1) and it was shown that the secondary acoustic peaks in the power spectrum of the cosmic microwave background (CMB) anisotropy should consequently be suppre ssed. We demonstrate that this prediction is confirmed by the recent Boomer ang and Maxima observations, which favour a step-like spectral feature in t he range k similar to (0.06-0.6) h Mpc (- 1), independently of the similar previous indication from the APM data. Such a spectral break enables an exc ellent fit to both APM and CMB data with a baryon density consistent with t he big bang nucleosynthesis (BBN) value. It also allows the possibility of a matter-dominated universe with zero cosmological constant, which we show can now account for even the evolution of the abundance of rich clusters.