Recent content by Ziofil

I see. Well you've certainly given me good ideas, and good examples that I can keep and think about! Thanks! PS can I restart/continue the topic somewhere else or would it be considered double posting?

My idea can be put in simpler terms, suppose we only have a noninteracting EM field. No currents, just fields. For instance, I can say that a component S\perp of the spin operator of the photon which is perpendicular to the k vector is unobservable, because it generates a transformation that...

When you say "the theory" are you referring to, say, all the currents that I can calculate from the Lagrangian? Or the Lagrangian itself? So if I had an operator O which mixes physical with unphysical degrees of freedom, which would turn a physical state into a nonphysical one (and perhaps...

So I can pick any gauge and the choice is just because of convenience. This makes me think that different gauges don't lead to different physics, for instance unphysical states in one gauge are unphysical in any other gauge, is that right? If it's correct then as the Coulomb gauge is not...

Hello I'm trying to understand how much freedom one has to pick a gauge to use for gauge fixing a free EM field and if so, on what conditions that freedom depends. Is there a particular reason (besides Lorentz covariance) to pick the Lorenz gauge? Are the alternatives (R\xi for instance) still...