  Different dynamical symmetry breaking patterns are explored for the two
dimensional phi4 model with higher order derivative terms. The one-loop saddle
point expansion predicts a rather involved phase structure and a new Gaussian
critical line. This vacuum structure is corroborated by the Monte Carlo method,
as well. Analogies with the structure of solids, the density wave phases and
the effects of the quenched impurities are mentioned. The unitarity of the time
evolution operator in real time is established by means of the reflection
positivity.
