The dynamics of a quantum nonlinear oscillator is studied in terms of its
quasi-flow, a dynamical mapping of the classical phase plane that represents
the time-evolution of the quantum observables. Explicit expressions are derived
for the deformation of the classical flow by the quantum nonlinearity in the
semiclassical limit. The breakdown of the classical trajectories under the
quantum nonlinear dynamics is quantified by the mismatch of the quasi-flow
carried by different observables. It is shown that the failure of classical
realism can give rise to a dynamical violation of Bell's inequalities.Comment: RevTeX 4 pages, no figure