Barnett's resolution of the Minkowski – Abraham dilemma holds, no 4-vector issue
Stéphane Maes
Abstract
There has been a century long controversy about the momentum density of photons in a medium, with two models getting experimental confirmation: the Minkowski model and the Abraham model. The latter being experimentations targeting the particle aspects of light, while the former focuses on its wave aspects. In 2010, Barnett proposed a simple resolution to the dilemma: both approaches are correct models, but one needs to distinguish what the momentum densities represent. The model is elegant and consistent with Maxwell’s equations in a medium. Subsequently, Changbiao Wang published two papers arguing that the reasoning is incorrect because the Abraham light momentum in the medium would not be a 4-vector. This paper shows that such a view is incorrect: the author incorrectly sets the kinetic momentum density of the medium to zero. Finally, we point out another paper that explains that the controversy is a relativistic effect between the reference frame in proper time for the wave and external observers.