The wave four-vector formula_16 is a corollary of the invariance of Maxwell equations (although widely ignored in the analysis of Abraham–Minkowski debate), and it was first shown by Einstein in his 1905 paper when setting up "theory of Doppler's principle and of aberration". Since formula_16 is a Lorentz four-vector, formula_18 must be a Lorentz invariant, leading to formula_19 being Lorentz invariant. In a recent excellent work, Partanen and coworkers claim that the energy formula_20 and momentum formula_21 for their MP quasiparticle also constitute a Lorentz four-vector, leading to formula_22 being Lorentz invariant. Since formula_19 and formula_22 are both Lorentz invariants, the frequency formula_25 and the refractive index formula_26 must also be Lorentz invariants for formula_27, which means that there is no Doppler effect in a dielectric medium. Such a conclusion could call Einstein's special relativity into question.