Pion-nucleon absorption operator ambiguity

In agreement with recent results it is shown that the pion-nucleon absorption operator depends on the nucleon single-particle potential's Lorentz transformation properties. This is essentially the same result as for the nuclear magnetic moment problem, these terms being of relativistic order [i.e., (νc)² corrections] in both problems. There exists a unitary equivalence of various forms of the absorption operator, but if handled consistently this leads to the same physical results.