Relativistic quantum field theory (RQFT) treatment of few-body systems

We express the total Hamiltonian H of interacting fields through new operators for particle creation and destruction and show that this can be understood as an unitary transformation (UT) of H. The respective particles may be called "clothed". They are identified with the physical particles. The Hamiltonian in the new form turns out to be dependent on the renormalized particle masses and not the "bare" ones. Forms of the same kind are derived for all the Poincare group generators. This fact makes it possible to do the transformations of "clothed" states under the Lorentz boosts. By using this new form of the Hamiltonian we suggest an approach to the bound state problem in relativistic quantum field theories. The eigenvalue equation derived here has much in common with those considered in the conventional nuclear physics.