Down to what size is there experimental justification for modelling the electron as a point like particle without volume? Asked in another way, at what size scale would it be more correct to model the electron as a charged shell with unknown internal structure instead of a geometric point without volume?

[I am not questioning whether or not the model is correct - only where the cutoff between theory and proof should be drawn when evaluating alternative theories]

EDIT The proposed duplicate question does not contain any answers that would suggest a 'proven maximum size' like I am asking about.

  • $\begingroup$ Where among the answers to that other question is there a numerical value that is related to my question? $\endgroup$
    – user263399
    Mar 6 '19 at 9:52
  • $\begingroup$ @user263399 In what case would anyone find themselves "modeling the electron as a charged shell with unknown internal structure"? How would one test such a model? (All of the electron-compositeness-scale/electron-radius tests I know of, for example in the PDG: pdg.lbl.gov/2015/reviews/…, require some model for how the internal structure works.) $\endgroup$ Mar 6 '19 at 10:07
  • $\begingroup$ I'm reading cybsoc.org/electron.pdf which toys with electrons being photons confined within a toroidal topology or some such (haven't finished yet) - but in such a case one would expect deviation between the point and shell at some scale. $\endgroup$
    – user263399
    Mar 6 '19 at 10:17
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    $\begingroup$ @AaronStevens - that is correct. All attempts to find a scattering interaction that does not allow for a point-like electron have had a null result. I've lost track of the current experimental bounds on the largest possible size, but its darned small... $\endgroup$
    – Jon Custer
    Mar 6 '19 at 14:06
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    $\begingroup$ Current experimental limit seems to be that the electron is smaller than $10^{-18}m$ in radius. $\endgroup$
    – Jon Custer
    Mar 6 '19 at 14:12