  We review the general quantization of scalar fields in curved space-times in
the Schroedinger formalism and discuss the determination of the ground-state.
By explicitly computing the norm of the ground-state wave functional, we give
an argument for the instability of the ground-state of a QFT in a
semi-classical space-time of Bianchi-type I. We find that this norm is, in
general, time-dependent, and conclude that the ground-state evolution is not
unitary.
