Diagram technique for the low-temperature phase in the chiral field model

Perturbation theory in powers of 1/N is constructed for the lower phase of the three-dimensional chiral field model. The diagrams of the model possess a peculiar property: although they include N propagation functions of the massless tield, there are only (N-1) Goldstone particles in the theory and the O(N) symmetry is violated. Formulated perturbation theory for the lower phase is renormalizable and free from infrared divergences. It is established that the Wilson expansion of a special form is valid for the lower phase