Speaker
Description
In this talk, I will provide a brief review of the reducible contributions
to QED amplitudes in a constant background field from the worldline
perspective. The focus will be on the missing piece in photon-graviton
conversion in a magnetic field. This process is typically studied at tree
level, but one-loop corrections involving scalars and spinors have also been
calculated. Unlike the tree-level process, the one-loop amplitude exhibits a dependence
on photon polarization, leading to dichroism. However, previous calculations
overlooked a tadpole contribution, which was historically assumed to vanish
in QED but was recently shown to have been incorrectly dismissed.
Here, we compute this missing diagram in closed form and demonstrate that it
does not contribute to dichroism.
