Periodic vacuum and particles in two dimensions - art. no. 065008

Different dynamical symmetry breaking patterns are explored for the two dim ensional phi(4) model with higher order derivative terms. The one-loop sadd le point expansion predicts a rather involved phase structure and a new Gau ssian critical line. This vacuum structure is corroborated by the Monte Car lo method, as well. Analogies with the structure of solids, the density wav e phases and the effects of the quenched impurities are mentioned. The unit arity of the time evolution operator in real time is established by means o f the reflection positivity.