  Schwinger pair production in spatially and temporally inhomogeneous electric
and magnetic fields is studied. The focus is on the particle phase-space
distribution within a high-intensity few-cycle pulse. Accurate numerical
solutions of a quantum kinetic theory (DHW formalism) are presented in momentum
space and, with the aid of coarse-graining techniques, in a mixed
spatial-momentum representation. Additionally, signatures of the
carrier-envelope phase as well as spin-field interactions are discussed on the
basis of a trajectory-based model taking into account instantaneous pair
production and relativistic single-particle dynamics. Although our simple
semi-classical single-particle model cannot describe every aspect of the
particle production process (quantum interferences), essential features such as
spin-field interactions are captured.
