Recent content by reggeon

Lethe's argument on gauge invariance got me interested also. Basically, I think the argument here is two fold, firstly gauge invariance of the EM field and the zero-mass of the photon go hand in hand (otherwise the field equations are just not gauge invariant.) Secondly, if the EM field is gauge...

The pleasure's mine. The URL is interesting - the lectures there are from the 1950's, and are part of a large collection of stuff by Leite Lopes, including some jointly authored with Richard Feynman.

No need for any answer to these questions - found a really great set of lectures on the representations of the poincare group and the resulting wave equations at: http://www4.prossiga.br/lopes/prodcien/lectures/ Thanks for the hints that got me to go an look for this.

Lethe, that's a great explanation - many thanks. I had suspected it must all be down to the zero mass of the photon. Is there any similar impact on spin states for the spin 1/2 neutrino? I like the argument around the Poincare group. Is there a spin-1 version of the Dirac spin 1/2 equation...

Photons have spin 1, yet only show two possible spin values along the direction of travel. For a spin 1 particle there should be three possible values, along the direction of motion, away from it and zero. What happens in the wave equation solutions to stop the zero spin state from coming into...