The dual sector of the \phi^4 Theory in 4D
  The one-component $\lambda\phi^4$ theory in four dimensions in the spontaneously broken symmetry phase has a non-trivial, non-perturbative sector which can be studied by means of a duality transformation of its Ising limit. Duality maps this theory to a model of interacting membranes. Physical states correspond to membrane excitations. The way this non-perturbative behaviour can be reconciled with the triviality of the theory in its continuum limit is discussed. 
F.Gliozzi and M.Leone