  We describe the dynamics of two component non-interacting ultracold Fermions
which are initially in thermal equilibrium and undergo a rapid quench to either
the repulsive or attractive side of a Feshbach resonance. The short time
dynamics is dominated by the exponentially growing collective modes. We study
the Stoner instability and formation of ferromagnetic textures on the repulsive
side, and the pairing instability towards BCS or FFLO-like states (determined
by the population imbalance) on the attractive side. In each case, we evaluate
the growth rate of unstable modes and predict the typical lengthscale of
textures to be formed.
