## Expansion of a mesoscopic Fermi system from a harmonic trap

We study the dynamics of time-of-flight expansion of an atomic Fermi system with a finite number of particles N after it is released from a harmonic trapping potential. We consider two different initial states: the Fermi sea state and the paired state. In the former case, we derive exact and simple analytic expressions for the dynamics of the particle density and density-density correlation functions, taking into account the level quantization and possible anisotropy of the trap. To describe the paired state, we use the projection of the grand-canonical BCS wave function onto the subspace with a fixed number of particles,more »