  We study the small mass limit of the one-loop spinor effective action,
comparing the derivative expansion approximation with exact numerical results
that are obtained from an extension to spinor theories of the
partial-wave-cutoff method. In this approach one can compute numerically the
renormalized one-loop effective action, for radially separable gauge field
background fields in spinor QED. We highlight an important difference between
the small mass limit of the derivative expansion approximation for spinor and
scalar theories.

High Energy Physics - Theory