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An interesting class of background field configurations in QED are theO(2)xO(3) symmetric fields. Those backgrounds have some instanton-likeproperties and yield a one-loop effective action that is highly nontrivial butamenable to numerical calculation, for both scalar and spinor QED. Here we usethe recently developed "partial-wave-cutoff method" for a numerical analysis ofboth effective actions in the full mass range. In particular, at large mass weare able to match the asymptotic behavior of the physically renormalizedeffective action against the leading two mass levels of the inverse mass (orheat kernel) expansion. At small mass we obtain good numerical results even inthe massless case for the appropriately (unphysically) renormalized effectiveaction after the removal of the chiral anomaly term through a small radialcutoff factor. In particular, we show that the effective action after thisremoval remains finite in the massless limit, which also provides indirectsupport for M. Fry's hypothesis that the QED effective action in this limit isdominated by the chiral anomaly term.

QED effective action for an O(2)xO(3) symmetric field in the full mass range