The Inflationary Paradigm: Predictions for CMB

We review why the search for a causal explanation of the large scale properties of the universe supports the idea that an extended period of accelerated expansion, called inflation, preceded primordial nucleosynthesis. As a consequence of inflation, all pre-existing classical structures are washed out, and the primordial density fluctuations (the seeds of the large scale structures) result from the amplification of vacuum quantum fluctuations. The properties of the spectrum are derived and compared to those of the spectrum of CMB anisotropies. The agreement is striking.