Recent content by SkeZa

\hat{\vec{L}} = \vec{r} \times \hat{\vec{p}} \times is the cross product... Do the math and then see if they commute ps [px , py] = [px , pz] = 0

I know that. The problem is how to simplify/rewrite that expression (the last one) into something solveable...

Homework Statement I'm supposed to show that the Lindhard dielectric functions gives a contribution to the effective potential of a metals as U_{eff}( \vec{r} ) \propto \frac{cos( 2 k_{F}r)}{r^{3}} in the limit of r\rightarrow\infty for d = 3 (3 dimensions) Homework Equations...

That's a relief. At least I don't have to "reinvent" Faynmans rules. But I'm still confused as to which channel/channels the diagrams will be. For actual particles, one gets clues as to which it might be but how does one figure it out for a field \phi

These where my thoughts at the beginning. I later found a reference in a book by F. Gross, but he's including the charged \Phi K-G fields as well. In the book, he tells that the first order pertubation (for 2 point) describes the decay the fields. Second order would then describe scattering (2...

I'm reading a course in Introduction to QFT and I'm stuck at a problem. I'm hoping someone here could point me in the right direction or say if my assumptions are incorrect. Homework Statement Derive the Feynman rules and all diagrams at tree-level for \lambda \phi^3 theory using Wick's...