We investigate the quantum kinetic approach to pair production from vacuum by a time-dependent electric field. Equivalence between this approach and the more familiar $S$-matrix approach is explicitly established for both scalar and fermion cases. For the particular case of a constant electric field, the exact solution for kinetic equations is provided and the accuracy of low-density approximation is estimated.

• Received 13 August 2010

DOI:https://doi.org/10.1103/PhysRevD.83.025011