- #1
Frank Castle
- 580
- 23
I'm fairly new to QFT and I'm currently trying to understand perturbation theory on this context.
As I understand it, when one does a perturbative expansion of the S-matrix and subsequently calculates the transition amplitude between two asymptotic states, each order in the perturbative calculation simply provides corrections to the leading order contribution, taking into account all the possible interactions that can take place in between the initial and final states. Provided that, as the order increases, the contributions become more and more suppressed relative the the leading order term, them we can trust our perturbative calculation and furthermore the first few terms in the expansion provide a good approximation to the true value of the transition amplitude.
First of all, is what I wrote in the previous paragraph the correct intuition for what's "going on"?!
Secondly, do the higher order contributions correspond to anything physical other than describing all the possible intermediate interactions that can take place between an initial and final state? Do they correspond to more energetic interactions or is it simply analogous to perturbation theory in QM in that the higher order terms just serve as corrections to the leading order term due to the quantum nature of the system?
Apologies if this is a stupid question, just want to get a correct intuition for what's going on
As I understand it, when one does a perturbative expansion of the S-matrix and subsequently calculates the transition amplitude between two asymptotic states, each order in the perturbative calculation simply provides corrections to the leading order contribution, taking into account all the possible interactions that can take place in between the initial and final states. Provided that, as the order increases, the contributions become more and more suppressed relative the the leading order term, them we can trust our perturbative calculation and furthermore the first few terms in the expansion provide a good approximation to the true value of the transition amplitude.
First of all, is what I wrote in the previous paragraph the correct intuition for what's "going on"?!
Secondly, do the higher order contributions correspond to anything physical other than describing all the possible intermediate interactions that can take place between an initial and final state? Do they correspond to more energetic interactions or is it simply analogous to perturbation theory in QM in that the higher order terms just serve as corrections to the leading order term due to the quantum nature of the system?
Apologies if this is a stupid question, just want to get a correct intuition for what's going on