Single particles and composite systems in a mathematically rigorous formulation of relativistic quantum field theory

We define quantum field theory by taking the Lagrangian action to be given as a sequence of mathematically well-defined functionals written in terms of operator fields fulfilling given \hbox{local} commutation relations. The renormalized solution fields have a fully defined Fock space expansion and are \hbox{multi-local}; thus Haag's theorem does not apply, i.e., the interaction picture exists. Also, the formalism allows immediately the definition of a wave function and the description of many-body bound-state systems.