Fluctuations in imploding Bose-Einstein condensates*

Quantum and thermal effects play important roles in the fluctuations of ultracold Bose gasses, yet the fluctuations remain difficult to probe experimentally in 3D bulk systems.  We report on a joint experimental-theoretical effort which seeks to amplify these fluctuations via a quench from positive to negative scattering length. Following such a quench, initial fluctuations in the gas, whether seeded by a lattice potential, thermal fluctuations, or quantum fluctuations, are amplified on a time-scale which is fast compared to the collapse of the cloud. These can be compared to a variety of theoretical models, which predict the static structure factor as a function of time and momentum in the collapsing gas.