Amplification of Local Instabilities in a Bose-Einstein Condensate with   Attractive Interactions
  We study the collapse of large homogeneous Bose-Einstein condensates due to intrinsic attractive interactions. We observe the amplification of a local instability by seeding a momentum state $\bf{p}$ and suddenly switching the scattering length negative via a Feshbach resonance. As required by momentum conservation, we also observe the appearance of atoms in the conjugate momentum state. The time scale for this depletion process is found to be comparable to that for global collapse, implying that this process will be the primary decay channel for large homogeneous condensates. 
J. K. Chin, J. M. Vogels, W. Ketterle