On the low-energy limit of the QED N-photon amplitudes: part 2

TL;DR

This paper calculates the impact of reducible two-loop contributions on low-energy N-photon amplitudes in QED, correcting previous models that only considered irreducible parts, thereby refining theoretical predictions.

Contribution

It provides the first explicit computation of reducible two-loop contributions to low-energy QED N-photon amplitudes, updating the theoretical framework.

Findings

Reducible contributions significantly affect two-loop N-photon amplitudes.

Previous models ignoring reducible parts are incomplete.

The corrected amplitudes improve the accuracy of low-energy QED predictions.

Abstract

In recent work, Gies and Karbstein have discovered that the two-loop Euler-Heisenberg Lagrangians for scalar and spinor QED have non-vanishing reducible contributions in addition to the well-studied irreducible ones. This invalidates previous applications of those Lagrangians to the computation of the two-loop $N$-photon amplitudes in the low energy limit. Here we compute the corrections to those amplitudes due to the reducible contributions.