  The reaction of collective oscillations excited in the interaction between
aperiodically growing Jeans-type gravity perturbations and stars of a rapidly
rotating disk of flat galaxies is considered. An equation is derived which
describes the change in the main body of equilibrium distribution of stars in
the framework of the nonresonant weakly nonlinear theory. Certain applications
of the theory to the problem of relaxation of the Milky Way at radii where
two-body relaxation is not effective are explored. The theory, as applied to
the Solar neighborhood, accounts for observed features, such as the shape for
the velocity ellipsoid of stars and the increase in star random velocities with
age.
