Approach towards N -nucleon effective generators of the Poincaré group derived from a field theory
It is shown that the ten generators of the Poincaré group acting in the Fock space of nucleons and mesons and based on standard Lagrangians can be blockdiagonalized by one and the same unitary transformation such that the space of a fixed number of nucleons is separated from the rest of the Fock space. The existence proof is carried through in a formal power series expansion in the coupling constant to all orders. In this manner one arrives at effective generators of the Poincaré group which act in the two subspaces separately.