Do quantum fields in QFT interact with each other constantly and continuously, or only from time to time?
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Related post by OP: https://physics.stackexchange.com/q/589528/2451 – Qmechanic Oct 26 '20 at 12:22
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Quantum fields interact constantly.
However when you consider the perturbation theory for each order of coupling constant your amplitudes look like originating from discrete and finite number of acts of interaction between free particles. These contributions are represented by Feynman diagrams which may be the source of your question. You should understand that this is just an artifact of perturbative description. Full amplitude with continuous interaction is given by sum of infinite number of such diagrams.
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let's say there is a process of scattering of a photon by an electron. The process has a certain amplitude, the square of the modulus of which determines the probability that the measurement will result in a result corresponding to the final state of this process. And if the interaction was not recorded, then what? does it mean that the interaction did not happen at all, or in the intermediate state we have a superposition <interaction did not happen / interaction occurred>, and if the amplitude of the first term is much larger, then the output will be negative? – Arman Armenpress Jan 09 '21 at 13:14