Recent content by Perturbation

I have it, it's absolutely amazing and in my opinion worth the price tag. I was going to get it a few months ago but I decided to wait until I got to uni' so that I could use the 15% discount that Cambridge students get on CUP books.

Oh, ok, thanks. Playing with the degrees of freedom had occurred to me; I just thought there might be some deeper reason for the decomposition that had something to do with representations or whatever. And yeah, it really is a very good book. I got it for Christmas and I've really enjoyed...

I'm reading Carlo Rovelli's book "Quantum Gravity". In the second chapter he writes down the Plebanski action by performing a decomposition of the complex Lorentz algebra into self-dual and anti-self dual parts, i.e. so(3, 1, C)=so(3, C)\oplus so(3, C). I sort of appreciate this fact and what it...

Gauge theories are geometric.

Some familiarity with relativistic quantum mechanics and Lagrangian/Hamiltonian mechanics/field theory would help, though they are skimmed over in most QFT texts. I've not read it, but Weinberg's "Foundations" volume looks like a fairly concise introductory QFT book that includes a fair amount...

Hey, I found a proof that the Noether charges do generate the symmetries of the theory whilst I was flicking through a book of mine (it's in a footnote Chp. 26 pg. 92 of Weinberg "Quantum Theory of Fields" Vol. III). Consider a Lagrangian (not density) L=L(q_n, \dot{q}_n). If the action has...

Depending on the theory, perturbation theory...? And yeah, it's an amplitude not a density matrix.

As in the Noether current associated with some symmetry?

Qutie alright

I shall give it a go for you, it's pretty straightforward, you've probably just made some small cock up somewhere, I do it all the time. \delta Z_2+\delta...

Bummer Perhaps in the "Beyond the Standard Model" forum?

Nobody...?

Hey, guys. I recently bought Weinberg's QFT Vol. III on Supersymmetry and I'm a bit stuck with part of the proof he gives for the Haag-Lopuszanski-Sohnius theorem in chapter 25.2. He starts off by giving the usual way of classifying representations of the Homo' Lorentz group by a pair of...

That's not a bad idea if it doesn't already exist...anyone else?

\langle\Omega |T\left\{\psi (x_n)\cdots\psi (x_1)\right\}|\Omega\rangle =\lim_{T\rightarrow\infty (1-i\epsilon )}\langle 0 |T\left\{\psi (x_n)_I\cdots\psi (x_1)_I\right\exp\left[{\textstyle -i\int^T_{-T} d^4x H_I}\right]\}|0\rangle}\left(\langle 0 |\exp\left[{\textstyle -i\int^T_{-T} d^4x...