# Tag Info

### S-matrix for $\phi^3$ theory

It vanishes because of a hat in phi.
1 vote

### Dimensional regularization vs. hard cutoff and their relation to the renormalization scale in 2d vs 4d to find $\beta$ functions

Here's a rough argument for why the latter part of your question going from a pole to beta function is valid. (As I mentioned in the comments, the use of an additional scale $M$ in addition to $\mu$ ...
• 7,521

• 325
Accepted

### Particle-hole symmetry in 2nd quantization

This is a good question that I have also had, so I'm answering this even though it is two years old! It looks like your definitions are all fine, but I would use \hat{\mathcal{P}}\...
• 55
1 vote

### Dirac propagator in Non-Abelian Theory

Hints: P&S is considering the free fermion propagator in eq. (16.4), i.e. the cubic $\bar{\psi} A\psi$ interaction term does not contribute. In the Lagrangian density (16.1) there are implicitly ...
• 167k

### Free energy from the vacuum?

As per energy conservation law (or "no free lunch theorem"),- whatever energy you'll put into a pair production - on annihilation it will return given energy back to the field, so that total ...
• 7,272