Momentum of an electromagnetic wave in dielectric media

TL;DR

This paper reviews the century-long debate over electromagnetic wave momentum in dielectrics, concluding that no single energy-momentum tensor is complete without considering the medium, making different proposed tensors effectively equivalent in predictions.

Contribution

It clarifies the longstanding Minkowski-Abraham debate by showing all tensors are equivalent when the medium's energy-momentum is included, resolving theoretical ambiguities.

Findings

All proposed tensors yield identical experimental predictions when medium contributions are included.

The debate over the correct tensor is a matter of personal choice rather than empirical evidence.

A complete description requires considering both electromagnetic and medium energy-momentum tensors.

Abstract

Almost a hundred years ago, two different expressions were proposed for the energy--momentum tensor of an electromagnetic wave in a dielectric. Minkowski's tensor predicted an increase in the linear momentum of the wave on entering a dielectric medium, whereas Abraham's tensor predicted its decrease. Theoretical arguments were advanced in favour of both sides, and experiments proved incapable of distinguishing between the two. Yet more forms were proposed, each with their advocates who considered the form that they were proposing to be the one true tensor. This paper reviews the debate and its eventual conclusion: that no electromagnetic wave energy--momentum tensor is complete on its own. When the appropriate accompanying energy--momentum tensor for the material medium is also considered, experimental predictions of all the various proposed tensors will always be the same, and the preferred form is therefore effectively a matter of personal choice.