  The planned generation of lasers and heavy ion colliders renews the hope to
see electron-positron pair creation in strong classical fields (so called
spontaneous pair creation). This adiabatic relativistic effect has however not
been described in a unified manner. We discuss here the theory of adiabatic
pair creation yielding the momentum distribution of scattered pairs in
overcritical fields. Our conclusion about the possibility of adiabatic pair
creation is different from earlier predictions for laser fields.
