Resonant e+e- production by time-varying electromagnetic field

As pointed out by Cornwall and Tiktopoulos (CT) strong, time-varying electric fields may produce e+e- pairs in a resonant fashion. This effect could be related to the sharp peaks in the e+e- spectrum observed in the GSI heavy-ion collision experiments. We attempt to go beyond the case of spatially uniform fields discussed by CT. We find that resonant e+e- production indeed takes place for electric fields derived from four-potentials of the form A1=A2=A0=0, A3=δ(t)b(x3) provided by b(x) has discontinuities with a jump at least equal to π. (orig.)