Mixed Cold-hot Dark Matter Model with Falling and Quasi-flat Initial Perturbation Spectra

The mixed cold-hot dark matter cosmological model (CHDM) with Ωtot = 1 and a falling power-law initial spectrum of Gaussian adiabatic perturbations (n > 1) is tested using recent obserbational 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 H0 < 60 km/s/Mpc (H0 < 55 for n = 1) and the neutrino energy density Ων < 0.25. So, the CHDM model provides the best possibility for the realization of the simplest variants of the inflationary scenario having the effective slope n ≈ (0.95 − 0.97) between galaxy and horizon scales, including a modest contribution of primordial gravitational wave background to large-angle ∆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.