# Tag Info

1

Griffiths has a quite good book, Introduction to Elementary Particles. The last chapter (I believe only in the revised edition) is all about gauge theories and culminates in the Higgs mechanism. This book can be read with just a bit of E&M, though a good deal of quantum mechanics will make the reading much quicker. Many of the specific examples can be ...

0

I'd like to give a different point of view than the one provided in Qmechanic's answer. The reason is not because of gauge invariance. Indeed, gauge invariance is just a statement of redundancy and it can't possibly have any physical consequences. My answer is instead the following: the photon is massless because it has just 2 degrees of freedom while ...

8

I) At the perturbative/diagrammatic level of photon self-energy/vacuum-polarization $\Pi^{\mu\nu}$ , the photon masslessness is protected by the Ward identity, which in turn is a consequence of - you guessed it - gauge invariance. For the explanation in the setting of QED, see e.g. Ref. 1. Fig. 1: A one-loop contribution to the photon ...

4

For a scalar field $\phi$, the most widely used convention, based on my experience, is to write the Lagrangian with kinetic and potential terms, followed by interactions like so, $$\mathcal{L}=\frac{1}{2}(\partial_\mu\phi)^2 - \frac{1}{2}m^2 \phi^2 - \sum_{n \geq 3} \frac{\lambda^n}{n!}\phi^n$$ where $\lambda_n$ are coupling constants. (We could not have a ...

Top 50 recent answers are included