- #1
tomdodd4598
- 138
- 13
- TL;DR Summary
- In φ^4 theory, the beta function is determined by analysing the amplitude of the vertex. Can we do the same in QED?
Hey there,
I am a little confused about the way most textbooks and notes I've read find the beta function for QED. They find it by looking at how the photon propagator varies with momentum ##q##, in particular in the context of a ##2\rightarrow2## scattering process which is proportional to ##e^2##, and arguing that the moving in the amplitude of the propagator can be interpreted in the movement of the value of the square of the coupling (e.g. Peskin and Schroeder pages 245-247).
In ##\varphi^4## theory, the story is rather different. Instead, we look at how the vertex amplitude varies with momentum, and the renormalisation of the field and mass is unrelated.
Can we not take a similar approach to determining the beta function for QED, i.e. look at how the vertex amplitude varies with momentum?
I am a little confused about the way most textbooks and notes I've read find the beta function for QED. They find it by looking at how the photon propagator varies with momentum ##q##, in particular in the context of a ##2\rightarrow2## scattering process which is proportional to ##e^2##, and arguing that the moving in the amplitude of the propagator can be interpreted in the movement of the value of the square of the coupling (e.g. Peskin and Schroeder pages 245-247).
In ##\varphi^4## theory, the story is rather different. Instead, we look at how the vertex amplitude varies with momentum, and the renormalisation of the field and mass is unrelated.
Can we not take a similar approach to determining the beta function for QED, i.e. look at how the vertex amplitude varies with momentum?