Photon in gauge theory

[Yoran91]

Hello everyone,

 

I'm writing an essay on the properties of the photon and how these are reflected in modern theories in physics.

Now I have already written loads about relativity, electrodynamics and basic quantum mechanics, but I seem to get stuck on QED and QFT.

In particular, I would like to know precisely how it follows that the photon has spin 1 and is electrically neutral.

 

On wikipedia I read that 'The quanta of an abelian gauge field must be massless, uncharged bosons, as long as the symmetry is not broken; hence, the photon is predicted to be massless, and to have zero electric charge and integer spin', click , but it turns out to be quite difficult finding a good textbook on this.

Can anyone explain this or point me towards a good source for information like this?

 

Thanks in advance,

Yoran.

[ajb]

In particular, I would like to know precisely how it follows that the photon has spin 1...

 

You need to think about irreduciable representations of the Lorentz group. It is a little technical, but in 4-d a vector potential can be used to describe the spin-1 irrep.

[uncool]

The classic book on QFT is Peskin and Schroeder's An Introduction to Quantum Field Theory. If I remember correctly, it does include how the electromagnetic gauge symmetry appears in the Lagrangian, which should be what you need.

=Uncool-

[Yoran91]

The classic book on QFT is Peskin and Schroeder's An Introduction to Quantum Field Theory. If I remember correctly, it does include how the electromagnetic gauge symmetry appears in the Lagrangian, which should be what you need.

=Uncool-

 

Yes, I keep finding information about a local gauge symmetry of the lagrangian density, but I haven't been able to find how this implies that the photon has spin 1 or no charge.

 

Edit:

I haven't been able to find anything on the spin or charge on a photon. It's assumed in most textbooks that s=1, q=0, but I can't seem to find a derivation anywhere...

Edited July 29, 2012 by Yoran91