Renormalization of heavy quark effective field theory: Quantum action principles and equations of motion

We discuss the quantum action principles and equations of motion for heavy quark effective field theory. We prove the so-called equivalence theorem for HQEFT which states that the physical predictions of HQEFT are independent from the choice of interpolating fields. In passing we point out that the HQFET is in fact more subtle than the quantum-mechanical Foldy-Wouthuysen transformation