Approach towards N-nucleon effective generators of the Poincaré group derived from a field theory

It is shown that the ten generators of the Poincar´e 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 Poincar´e group which act in the two subspaces separately.