Crossing symmetry in the high-energy limit and pair production in ultrarelativistic heavy-ion collisions

We briefly review the description of electron propagation in the field of ultrarelativistic colliding nuclei. The crossing symmetry of the resulting amplitude is discussed. We show that the amplitude loses crossing invariance in the high-energy limit so that the conventional formalism to derive the pair production amplitude cannot be applied. Consequently, former calculations of the pair production amplitude using the solution of the two-center Dirac equation are incorrect. On the basis of bremsstrahlung and e⁺e^- pair production, conclusions about the Coulomb corrections in electron scattering and pair production in ultrarelativistic heavy-ion collisions are drawn.