Bogoliubov group variables in relativistic field theory

We define the Bogoliubov variables for strongly coupled systems that are invariant under the Poincaré group in (1+1)-dimensional space-time. This allows us to achieve a compatibility between taking the conservation laws into account exactly and developing a regular perturbation theory. We perform the secondary quantization in terms of the Bogoliubov variables and discuss the problem of reducing the number of states of the field. We also discuss the conditions for validity of the perturbation theory. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 111, No. 2, pp. 242–251, May, 1997.