Space-time effects in the decay of strings by pair-creation

To overcome certain deficiencies of the Schwinger pair-creation formula as used in string break up models we calculate the production rate in finite time-dependent electric field configurations. For computational reasons we look for analytic solutions of the dynamics. This we have achieved in the case of massless fermions in 1+1 dimension. The pathological nature of this case forces us to look at special field configurations or to use a small mass approximation. In both situations we find a suppression of the production rate for small space-time volumes available for pair production. (orig.)