  In one scenario of baryogenesis, the matter-antimatter asymmetry was
generated in the early universe during a cold electroweak transition. We model
this transition by changing the sign of the effective mass-squared parameter of
the Higgs field from positive to negative. The resulting `tachyonic'
instability leads to a rapid growth of occupation numbers, such that a
classical approximation can be made in computing subsequent developments in
real time.
  We solve the classical equations of motion in the SU(2)-Higgs model under the
influence of effective CP-violation. The resulting baryon asymmetry follows
from the generated Chern-Simons number using the anomaly equation. The
`classical' difficulties with lattice implementations of these observables are
avoided here because the fields are smooth on the lattice scale.
