Mixed Cold-Hot Dark Matter Model with Falling and Quasi-Flat Initial Perturbation Spectra

The mixed cold-hot dark matter cosmological model (CHDM) with Omega(tot) = 1 and a falling power-law initial spectrum of Gaussian adiabatic perturbations (n > 1) is tested using recent observational data. It is shown that its fit to the data becomes worse with the growth of n - 1 and may be considered as unreasonable for n > 1.1 for all possible values of the Hubble constant. Thus, the CHDM model with a falling initial spectrum is worse than the same model with the approximately flat (\n - 1\ < 0.1) spectrum. On the other hand, the CHDM model provides a rather good fit to the data if n lies in the range (0.9 - 1.0), the Hubble constant H-0 < 60 km s(-1) Mpc(-1) (H-0 < 55 for n = 1) and the neutrino energy density Omega, < 0.25. So, the CHDM model offers the best possibility for the realization of the simplest variants of the inflationary scenario having the effective slope n approximate to (0.95 - 0.97) between galaxy and horizon scales, including a modest contribution of primordial gravitational wave background to large-angle Delta T/T fluctuations of the cosmic microwave background (resulting in the increase of their total rms amplitude by 5%-10% expected in some variants). A classification of cosmological models according to the number of fundamental parameters used to fit observational data is presented, too.