Evolution of the main mode of density perturbations in a neutrino-dominated universe.

The paper examines the physical features of the evolution of the growing mode of density perturbations in homogeneous isotropic cosmological models. The evolution of density perturbations in the long-wave limit in a neutrino-dominated Friedman universe is determined in the ultrarelativistic asymptotic case and in the general case. It is shown that all natural modes of long-wave scalar perturbations in a relativistic neutrino-dominated universe contain corresponding quadrupole components of the perturbed neutrino-distribution function. With neutrino separation from the Pascal fluid, quadrupole distributions of various modes mutually compensate one another; however, further on there occurs a disharmony of quadrupole moments owing to the difference in the laws of evolution of the natural modes of perturbations.