CDM MODELS WITH A BSI STEP-LIKE PRIMORDIAL SPECTRUM AND A COSMOLOGICAL CONSTANT

A class of spatially flat models with cold dark matter (CDM), a cosmol ogical constant and a broken-scale-invariant (BSI) step-like primordia l (initial) spectrum of adiabatic perturbations, generated in an exact ly solvable inflationary model where the inflaton potential has a rapi d change of its first derivative at some point, is confronted with exi sting observational data on angular fluctuations of the CMB temperatur e, galaxy clustering and peculiar velocities of galaxies. If we locate the step in the initial spectrum at k similar or equal to 0.05 h Mpc( -1), where a feature in the spectrum of Abell clusters of galaxies was found that could reflect a property of the initial spectrum, and if t he large-scale flat plateau of the spectrum is normalized according to the COBE data, the only remaining parameter of the spectrum is p - th e ratio of amplitudes of the metric perturbations between the small-sc ale and large-scale flat plateaux. Allowed regions in the plane of par ameters (Omega = 1 - Omega(Lambda), H-0) satisfying all data have been found for p lying in the region (0.8-1,7). Especially good agreement of the form of the present power spectrum in this model with the form of the cluster power spectrum is obtained for the inverted step (p < 1 ,p = 0.7-0.8), when the initial spectrum has slightly more power on sm all scales.