UNSTABLE STATES IN QED OF STRONG MAGNETIC-FIELDS

We question the use of stable asymptotic scattering states in QED of s trong magnetic fields. To correctly describe excited Landau states and photons above the pair creation threshold the asymptotic fields are c hosen as generalized Licht fields. In this way the off-shell behavior of unstable particles is automatically taken into account, and the res onant divergences that occur in scattering cross sections in the prese nce of a strong external magnetic field are avoided. While in a limiti ng case the conventional electron propagator with Breit-Wigner form is obtained, in this formalism it is also possible to calculate S-matrix elements with external unstable particles.