Do they formally appear in any book? Or his Lectures?

  • $\begingroup$ I think it appears in this paper. journals.aps.org/pr/abstract/10.1103/PhysRev.76.749 $\endgroup$ – Sayan Mandal Oct 6 '17 at 1:01
  • $\begingroup$ I'm voting to close this question as off-topic because it is about historic events rather than actual physics. $\endgroup$ – Qmechanic Oct 6 '17 at 4:06
  • $\begingroup$ That's fine, I'm just thinking about somebody else looking for this answer, which I was not able to find anywhere else. $\endgroup$ – Carlos Oct 6 '17 at 16:13
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    $\begingroup$ @Qmechanic Hm, I actually thought the question was fine. This is the sort of thing the specific-reference tag was made for. $\endgroup$ – David Z Oct 6 '17 at 18:35
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    $\begingroup$ IIRC, Stückelberg was using diagrams to compute perturbative expansions long before Feynman. Can anyone confirm this? $\endgroup$ – AccidentalFourierTransform Oct 6 '17 at 19:04

Feynman's paper, "Space-Time Approach to Quantum Electrodynamics", where he introduced the diagrammatic point of view, was published in 1949 and is available online.

As for the context in which Feynman diagrams appear: Imagine you want to know how a particle travels from $A$ to $B$. You can split up the time evolution operator $\text{e}^{-\text{i} Ht}$ into many small steps and integrate over every possible position, that the particle could go to at every infinitesimal step.

You get an expression with an exponential, so you can perform a Taylor expansion, assuming the coupling between the different particles/fields is small.

So, the probability of a given process is now an infinite series of terms, ordered by the coupling constant. And it is these terms that Feynman represented graphically.

  • $\begingroup$ I think the question makes a lot more sense if it's asking about a historical perspective. (Especially given that it has the specific-reference tag.) Personally, I would feel comfortable assuming that unless the OP indicates otherwise. $\endgroup$ – David Z Oct 6 '17 at 1:30
  • $\begingroup$ @DavidZ thanks for the remark, I edited my answer to focus on the historical aspect! $\endgroup$ – Stephan Oct 6 '17 at 1:46
  • $\begingroup$ I agree with you @David Z $\endgroup$ – Carlos Oct 6 '17 at 16:09

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