  We consider pion-nucleon scattering in heavy-baryon chiral perturbation
theory to third order. All electromagnetic corrections appearing to this order
are included. We thus have a consistent description of strong and
electromagnetic effects, which allows us to isolate the strong part of the
interaction in an unambiguous way. We give pion-nucleon phase shifts up to pion
laboratory momenta of 100 MeV and find sizeable differences for the S-waves of
the elastic channels compared to previous phase shift analyses. The precise
description of the scattering process also allows us to address the question of
isospin violation in the strong interaction. For the usually employed triangle
relation we find an isospin breaking effect of -0.7% in the S-wave, whereas the
P-waves show an effect of -1.5% and -4 to -2.5%, respectively, for pion
laboratory momenta between 25 and 100 MeV.
