Observation of induced subcritical bifurcation by near-resonant perturbations

We present the first experimental evidence that near-resonant perturbations produce a destabilizing shift of a subcritical bifurcation. This is in direct contrast to supercritical bifurcations, where near-resonant perturbations always suppress the instability. Using a normal form analysis we derive a generic scaling law relating the magnitude of the destabilizing shift to the perturbation amplitude and detuning frequency. The predictions are in excellent agreement with our experiments. In the limit of very small the shift obeys a pure scaling law, () ^2/3.