Evolution of orbits in the outer part of the asteroidal belt and in the Kirkwood gaps

It is well known that the semi-major axes of the asteroids between the orbits of Mars and Jupiter are not uniformly distributed. The depleted regions in the outer part and the Kirkwood gaps in the inner part of the belt represent singularities in the frequency distribution of the asteroidal semi-major axes. The question whether these depleted regions and the Kirkwood gaps are due to gravitational perturbations of Jupiter or due to cosmogonic effects has not yet been solved and the discussion is still continuing. (Auth.)