On the effect of time-dependent inhomogeneous magnetic fields in electron-positron pair production

Electron-positron pair production in space- and time-dependent electromagnetic fields is investigated. Especially, the influence of a time-dependent, inhomogeneous magnetic field on the particle momenta and the total particle yield is analyzed for the first time. The role of the Lorentz invariant ${\mathbf{E}}^2-{\mathbf{B}}^2$, including its sign and local values, in the pair creation process is emphasized.