I just learned about the quantization of the em field. Then EM field 4-potential has components A^mu, giving you 4 degrees of freedom. That gets reduced to 2 degrees of freedom (2 polarization states), that gets done to impose the Lorenz gauge onto free photons. SO what the hell happens to the so called "scalar" A^0 and "longitudinal" A^3 polarization states. How is it that the EM field has 4 degrees of freedom in one case and 2 in an other.