BLUE PERTURBATION SPECTRA FROM INFLATION

It is generally believed that inflationary models for the origin of pr imordial density perturbations predict a spectral index n less than or equal to 1. However, some observations, such as the first two years o f COBE data, the Tenerife temperature anisotropy detection, bulk motio ns, and structures on the similar to 50h(-1) Mpc scale, have recently aroused much interest in spectral indices n > 1 (''blue spectra''). We show that there is a class of inflationary models leading to this kin d of spectra: they are produced while the inflaton field rolls down to a potential minimum with the potential energy dominated by a cosmolog ical-constant-like piece.