Stefan Teufel and Gianluca Panati Propagation of Wigner functions for the Schroedinger equation with a perturbed periodic potential (44K, LaTeX) ABSTRACT. Let $V_\Gamma$ be a lattice periodic potential and $A$ and $\phi$ external electromagnetic potentials which vary slowly on the scale set by the lattice spacing. It is shown that the Wigner function of a solution of the Schroedinger equation with Hamiltonian operator $H = \frac{1}{2} ( -i \nabla_x - A(\epsilon x) )^2 + V_\Gamma (x) + \phi(\epsilon x)$ propagates along the flow of the semiclassical model of solid states physics up an error of order $\epsilon$. If $\epsilon$-dependent corrections to the flow are taken into account, the error is improved to order $\epsilon^2$. We also discuss the propagation of the Wigner measure. The results are obtained as corollaries of an Egorov type theorem proved in a previous paper (mp_arc 02-516)