Recent content by ingenue

So are you saying that because f is very large, the term aF\tilde{F}/f is very small, so that we no longer worry the CP violating effect caused by it?

No, I meant why did it happen to pick out the right vacuum?

I'm just reading Srednicki's QFT book, where the author gave an exercise on this axion. He posed the Lagrangian as (\partial_\mu a)^2+(\theta+a/f)F\tilde{F}, then he said we can use the shifting symmetry of a to kill the theta term. But even if we do that, we're left with the term...

When people discuss the Schwinger model, sometimes they still call the electron field spin-1/2 and the EM field spin-1. I wonder if there's some justification for these calling, since there's no rotations at all in 1+1 spacetime. I know for SO(n) with n>=2, one can always have well-defined spins.

that's exactly why I'm asking. why did it happen to do this?

Consider the simplest \phi^4 with Z_2 breaking. Before the shift, \langle\phi\rangle=0 by symmetry. After the shift, the vev of the shifted field is zero, which means \langle\phi\rangle\neq0, which in turn means we have picked the corresponding vacuum out of two possibilities. However, through...

I had read it. It doesn't address my question. For example, the equation (34.19) in the online version of that book shows that a field carries two symmetric spinor indexes is spin-1, so why can't we use this to describe spin-1 fields?

In what sense are scalar, vector and tensor more "fundamental" than spinor? They're both representations of the Lorentz group.

It's a famous claim that spin-0, spin-1 and spin-2 fields are described by scalar, vector and second-rank tensor, respectively. My question is: why not other objects? For example, consider spin-1 field, we can use a field that carries two left spinor indexes. From the group-theoretic relation we...