The heavy mass limit in field theory and the heavy quark effective theory

We present a derivation of a large mass effective action from the complete theory of elementary interactions, via a sequence of field redefinitions. In this way one derives straightforwardly the 'matching conditions' of the static effective field theory. Gauge dependent properties of the effective theory are analysed, and relationships between the complete and effective theory are established. We give a general proof that there are no 1/m corrections to the absolute normalization condition of current-induced flavour changing transitions. (orig.)