Exact solutions and triviality of lambda (phi^*phi)² theory in the Feshbach-Villars formulation

The complex scalar quantum field theory with a lambda (phi^*phi)^2 interaction is considered in the Feshbach-Villars formulation. It is shown that exact few-particle eigenstates of the QFT Hamiltonian can be obtained. The resulting relativistic few-body equations correspond to Klein-Gordon particles interacting via delta-function, or ``contact'', potentials. Momentum-space solutions of the two-body equation yield a `trivial' unity S-matrix.