A recent approach (see Phys.org coverage) suggests that the missing piece in the Abraham–Minkowski debate is spin — the intrinsic angular momentum of light.
By projecting momentum onto spin, the two definitions align:
Details: Phys. Rev. A 112, 033721 (2025) DOI: 10.1103/sxh8-q8tq
Thanks for the thoughtful comment. In this work, “spin” arises from casting Maxwell’s equations in a Dirac-like form, where the photon is treated as a spin-1 particle (unlike the electron’s spin-½ in the Dirac equation). In this framework, spin is a good quantum number, and its precession around momentum encodes polarization dynamics. The key result is straightforward: Minkowski momentum corresponds to the magnitude of the spin-projected momentum, while Abraham momentum is its averaged vector. Rather than being rival definitions, they describe complementary aspects of the same spin-projected structure.
Other works sometimes frame this as “canonical” vs. “kinetic,” but here the physics is more transparent: it’s about magnitude vs. averaged vector, grounded in the photon’s spin-1 character.