  We investigate the Quantum Resonance (QR) regime of a periodically kicked
atomic Bose-Einstein condensate. We find that the clearest indicator of the
nonlinear dynamics is a surprisingly abrupt cut-off which appears on the main
"Talbot time" QR. We show that this is due and excitation path combining both
Beliaev and Landau processes, with some analogies to nonlinear self-trapping.
Investigation of dynamical instability reveals further symptoms of nonlinearity
such as a regime of exponential oscillations.
