  Effects due to vacuum fluctuations in a semi-classical model of a massless
scalar field interacting with a rotating ring are investigated by introducing a
collective coordinate for the motion of the background potential. The model is
solved for a repulsive periodic $\delta$-distribution background of arbitrary
strength. The Casimir energy of this system is calculated in the co-rotating
and, by Legendre transformation, in the stationary laboratory frame. The
zero-point contribution to the angular momentum in this model is bounded below
by $|\ell_{ZP}|\leq\hbar/24$ and the ground state of the entire system thus
generally is non-rotating with a positive moment of inertia that decreases only
slightly with increasing angular rotation frequency. There is no transfer
between the zero-point and classical contributions to the total angular
momentum and energy of this system at zero temperature.
