On rotations in front-form dynamics

Quantum field theories in front-form dynamics are not manifestly rotational ly invariant. We study a model bound-state equation in 3+1 dimensional fron t-form dynamics, which was shown earlier to reproduce the Bohr and hyperfin e structure of positronium. We test this model with regard to its rotationa l symmetry and find that rotational invariance is preserved to a high degre e. Also, we find and quantify the expected dependence on the cut-off.