On a Quantum Field Theory with Degenerate Vacuum and a Special Type of Symmetry

We investigate a frame of a model of quantum field theory with a degenerate vacuum. At least one vacuum is cyclic. The field is covariant under a ``gauge'' transformation. We show the existence of non‐gauge‐invariant vacuum states. We define ``observables'' as gauge‐invariant operators; the algebra of these does not coincide with the algebra of the field operator; the reduction of the former algebra reflects a superselection rule.