Balazs thought experiment and its implications for the electromagnetic force density in continuous media. Relativistic analysis

Abstract

We analyze the Balazs thought experiment under minimal assumptions and show that the two expressions for the force density that have been recently discussed in the literature (the conventional Lorentz force density and the generalized or Einstein–Laub force density) are fully consistent with conservation of energy, conservation of momentum and the center-of-energy theorem. This conclusion contradicts some of the previously published claims that the conventional Lorentz force density is inconsistent with the center-of-energy theorem. We identify the sources of errors in these claims. We conclude that the conventional Lorentz force density captures all experimentally-observable effects of interaction of electromagnetic fields with matter and no other law or postulate (such as a resolution of the so-called Abraham–Minkowski dilemma) is necessary.