Dynamical density functional theory with hydrodynamic interactions and colloids in unstable traps.

A density functional theory for colloidal dynamics is presented which includes hydrodynamic interactions between the colloidal particles. The theory is applied to the dynamics of colloidal particles in an optical trap which switches periodically in time from a stable to an unstable confining potential. In the absence of hydrodynamic interactions, the resulting density breathing mode exhibits huge single peaked oscillations in the trap center which become double peaked and damped by hydrodynamic interactions. The predicted dynamical density fields are in good agreement with Brownian dynamics computer simulations.