  The scalar Yukawa model, in which a complex scalar field interact via a real
scalar field, is reduced by using covariant Green functions. It is shown that
exact few-particle eigenstates of the truncated QFT Hamiltonian can be obtained
in the Feshbach-Villars formulation if an unorthodox "empty" vacuum state is
used. Analytic solutions for the two-body case are obtained for massless chion
exchange in 3+1 dimensions and for massive chion exchange in 1+1 dimensions.
Comparison is made to ladder Bethe-Salpeter, Feynman-Schwinger and
quasipotential results for massive chion exchange in 3+1. Equations for the
three-body case are also obtained.
