Journal of Statistical Physics, Vol. 94, Nos. 56, 1999, p. 893-912.
We consider quasi-free quantum systems and we derive the Euler equation using
the so-called hydrodynamic limit. We use Wigner's well-known distribution
function and discuss an extension to band distribution functions for particles in
a periodic potential. We investigate the bosonic system of hard rods and
calculate fluctuations of the density.