  The contribution of quantum shape fluctuations to inertial properties of
rotating nuclei has been analysed within the self-consistent one-dimensional
cranking oscillator model. It is shown that in even-even nuclei the dynamical
moment of inertia calculated in the mean field approximation is equivalent to
the Thouless-Valatin moment of inertia calculated in the random phase
approximation if and only if the self-consistent conditions for the mean field
are fulfilled.
