Field Redefinitions and Wave Function Renormalization to $O(p^4)$ in Heavy Baryon Chiral Perturbation Theory

Mass- and wave-function renormalization is calculated to order $p^4$ in heavy baryon chiral perturbation theory. Two different schemes used in the literature are considered. Several technical issues like field redefinitions, non-transformation of sources as well as subtleties related to the definition of the baryon propagator are discussed. The nucleon axial-vector coupling constant $g_A$ is calculated to order $p^4$ as an illustrative example.