Inverse approach to solutions of the Dirac equation for space-time dependent fields

Exact solutions of the Dirac equation in external electromagnetic background fields are very helpful for understanding non-perturbative phenomena in quantum electrodynamics (QED). However, for the limited set of known solutions, the field often depends on one coordinate only, which could be the time $t$, a spatial coordinate such as $x$ or $r$, or a light-cone coordinate such as $ct-x$. By swapping the roles of known and unknown quantities in the Dirac equation, we are able to generate families of solutions of the Dirac equation in the presence of genuinely space-time dependent electromagnetic fields in $1+1$ and $2+1$ dimensions.