The discussion revolves around the calculations involved in quantum electrodynamics (QED), specifically focusing on the repulsion and attraction of charged particles through the use of Feynman diagrams and S-matrix elements. Participants explore the necessity of performing calculations to at least second order and reference various sources for further understanding.
Participants express varying levels of understanding regarding QED calculations, with some seeking clarification and others providing guidance. There is no consensus on the specific details of second order calculations or the adequacy of the referenced source.
Some participants indicate that a foundational understanding of quantum field theory is necessary to engage with the topic effectively, suggesting that assumptions about prior knowledge may limit the discussion.
So, I calculate and draw the Feynman diagram, from which I get the S matrix elements from which I get the cross section of scattering processes which tells me how everything is going to repel/attract, right?vanhees71 said:You just draw the Feynman diagram and calculute it according to the rules derived from the formalism. Feynman diagrams are just an ingenious shortcut to do these perturbative calculations. What you get are transition-matrix elements (S-matrix elements) from which you can calculate cross sections of scattering processes.
This might sound dumb, but what exactly is 2nd order.Vanadium 50 said:Note that you will need to calculate this to at least second order, because at leading order the scattering is the same either way.
ILoveParticlePhysics said:This might sound dumb, but what exactly is 2nd order.