Tadpole contribution to magnetic photon-graviton conversion

TL;DR

This paper investigates the one-loop corrections to photon-graviton conversion in a magnetic field, revealing that a previously overlooked tadpole diagram does not affect dichroism, refining the understanding of quantum effects in this process.

Contribution

The authors compute the previously neglected tadpole diagram in photon-graviton conversion, demonstrating it does not contribute to dichroism, thus correcting earlier assumptions.

Findings

The tadpole contribution is non-zero but does not influence dichroism.

One-loop corrections depend on photon polarization, affecting conversion amplitude.

The corrected calculation refines the quantum description of photon-graviton interactions.

Abstract

Photon-graviton conversion in a magnetic field is a process that is usually studied at tree level, but the one-loop corrections due to scalars and spinors have also been calculated. Differently from the tree-level process, at one-loop one finds the amplitude to depend on the photon polarization, leading to dichroism. However, previous calculations overlooked a tadpole contribution of the type that was considered to be vanishing in QED for decades but erroneously so, as shown by H. Gies and one of the authors in 2016. Here we compute this missing diagram in closed form, and show that it does not contribute to dichroism.