LAUSR

Abstract In this paper, I introduce two new concepts (Minkowski quasi-photon and invariance of physical definitions) to elucidate the theory developed in my previous work [Can. J. Phys. 93 (2015) 1510], and to clarify the criticisms by Partanen and coworkers [Phys. Rev. A 95 (2017) 063850]. Minkowski quasi-photon is the carrier of the momentum and energy of light in a medium under the sense of macroscopic averages of light-matter microscopic interactions. I firmly argue that required by the principle of relativity, the definitions of all physical quantities are invariant. I shed a new light on the significance of the symmetry of physical laws for resolution of the Abraham–Minkowski debate on the momentum of light in a medium. I illustrate by relativistic analysis why the momentums and energies of the electromagnetic subsystem and the material subsystem form Lorentz four-vectors separately for a closed system of light-matter interactions, and why the momentum and energy of a non-radiation field are owned by the material subsystem, and they are not measurable experimentally. Finally, I also provide an elegant proof for the invariance of physical definitions, and a clear definition of the Lorentz covariance for general physical quantities and tensors.