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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.

user263399
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  • Where among the answers to that other question is there a numerical value that is related to my question? – user263399 Mar 06 '19 at 09:52
  • @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: http://pdg.lbl.gov/2015/reviews/rpp2015-rev-searches-quark-lep-compositeness.pdf, require some model for how the internal structure works.) – probably_someone Mar 06 '19 at 10:07
  • I'm reading http://www.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. – user263399 Mar 06 '19 at 10:17
  • @user263399 But that's not a model in which the electron would be a charged shell with unknown internal structure. That's a model in which the electron has known internal structure (and the proposed internal structure doesn't necessarily support a charged-shell interpretation, anyway). – probably_someone Mar 06 '19 at 10:29
  • but outside a shell of a specific radius and with a specific surface charge it would be indistinguishable when replaced by a point charge at its centre – user263399 Mar 06 '19 at 10:41
  • I don't think there is any experimental evidence of the electron not being a point particle, right? (Note, particle physics is not my area of expertise) – BioPhysicist Mar 06 '19 at 12:57
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    @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... – Jon Custer Mar 06 '19 at 14:06
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    Current experimental limit seems to be that the electron is smaller than $10^{-18}m$ in radius. – Jon Custer Mar 06 '19 at 14:12
  • @JonCuster - do you have a source for that number please? – user263399 Mar 06 '19 at 16:31
  • https://www.nature.com/articles/nature10104 would be a place to start. – Jon Custer Mar 06 '19 at 16:42

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