# Universality of the Abraham-Minkowski dilemma for photon momenta beyond dielectric materials

## TL;DR

This paper demonstrates that the Abraham-Minkowski dilemma, which concerns the duality of photon momentum in dielectrics, is a universal phenomenon extending to wave-particle interactions, plasmas, and waveguides, involving electromagnetic stress considerations.

## Contribution

It extends the Abraham-Minkowski dilemma framework beyond dielectrics to include wave-particle interactions and waveguides, highlighting its universal nature and the role of electromagnetic stress.

## Key findings

- Dual photon momenta exist in plasmas and waveguides.
- The dilemma involves electromagnetic stress flux.
- Universality of the Abraham-Minkowski dilemma is established.

## Abstract

The authors) Whenever light is slowed down, for any cause, two different formulas give its momentum. For dielectrics, the coexistence of those momenta was the heart of the century-old Abraham-Minkowski dilemma, recently resolved. We demonstrate that this framework extends to momentum exchange in wave-particle interaction; in particular to Langmuir waves for Landau damping and to vacuum waveguides of electron tubes (metallic slow-wave structures). Focussing on the latter, we show that the dilemma resolution is not limited to discriminating between kinematic and canonical momenta but also involves a non-negligible momentum flux from Maxwell's electromagnetic stress. The existence of two momenta in materials, plasmas, and waveguides, for which light velocity modification has entirely different origin, points to the universality of the Abraham-Minkowski dilemma.