A TILTED COLD DARK MATTER COSMOLOGICAL SCENARIO

We motivate and explore a cold dark matter (CDM) cosmological scenario with a slightly tilted (0.6 < n < 1) spectrum of the initial perturbation spectrum compared to the standard (n = 1) CDM model. This minimal deviation from scale free primordial fluctuations is predicted by various inflationary scenarios and is compatible with COBE DMR results. The tilted CDM model with n almost-equal-to 0.7-0.8 alleviates many of the problems of the scale-free CDM model, both on large and on small scales, while other ranges of the index are excluded by various tests. For n = 0.7-0.8 the bias of galaxies over dark matter on the (5-10)h-1 Mpc scale is in the range 2.0-1.5, within the domain of physical plausibility. The one-dimensional galaxy velocity dispersion on the same scales would be in range (500-580)b(nu) km s-1 versus 750b(nu) km s-1 for standard CDM. A velocity bias, b(nu) = 0.7-0.8, consistent with physical modeling, brings the velocity dispersion into a range in accord with the low observed values.