Structure of a composite system in motion in relativistic quantum mechanics

Unlike in nonrelativistic quantum mechanics, the structure of a relativistic system of bound particles is intrinsically coupled with the overall translational motion of the system. This is illustrated by means of a solvable two-body model in one space dimension. The model is described in terms of the two-body Dirac equation with an interaction in the form of the δ function. Although the equation is not manifestly covariant, relativistic …