DENSITY-FLUCTUATIONS ON SUPER-HUBBLE SCALES

According to causality, the existence of density perturbations on scal es larger than the present Hubble radius y = 2c/H-0 is crucial for dis criminating between inflation and non-inflation models of the origin o f inhomogeneity of the universe. Observations of the cosmic background radiation anisotropies favor a super-Hubble suppression on scales lam bda(max) in the range 0.5 - 3.0y. Many of non-inflation models are con sistent with such a suppression. Inflation models are certainly not in conflict with this suppression; however one important parameter, the duration of the epoch of inflation, may need to be fine-tuned.