Abstract
We study space-time resolved densities of particle-hole pairs produced by an external time-dependent field acting on non-interacting non-relativistic particles. It is shown that, at least in some cases, the densities are not affected by Fermi-Dirac or Bose- Einstein statistics, and are determined only by the initial state of the multi-particle system. The second quantisation technique is extended to Dirac electrons and, with some modifications, to Klein-Gordon bosons. The difference in pair production in these two relativistic cases is analysed in some detail.