We present a brief introduction to the problem of large scale structure formation and how it relates to the cosmological parameters and to the physics of the early Universe. As an illustration, we also discuss recent observations of the CMB fluctuations (eg Boomerang and Maxima) which show an anomalously low second acoustic peak, which was initially interpreted as an indication of a high primordial Big-Bang nucleosynthesis (BBN) baryon density. We argue that this low peak can also be caused by ‘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 ∼ O.lhMpc−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.
KeywordsCosmic Microwave Background Cold Dark Matter Cosmological Parameter Baryon Density Inflaton Field
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