I think hansda got confused a few lines above the one I just quoted: I think hansda saw that completely unsourced line about the Penning traps (which appears to be talking in terms of classical physics anyway), and ran with it. In doing so, (s)he forgot to read the rest of that section, where it clearly explains it's an unsettled issue. Edit: Interestingly enough, there's similar discussions on the talk page: https://en.wikipedia.org/wiki/Talk:Electron#Radius https://en.wikipedia.org/wiki/Talk:...g_"caused_by"_virtual_photons,_"causes"_spin? But there too, the statement is unsourced. Edit2: Yes, it's a fully unsourced addition: https://en.wikipedia.org/w/index.php?title=Electron&diff=prev&oldid=633949990 Thus it can safely be disregarded.
https://en.wikipedia.org/wiki/Compton_wavelength . Compton wavelength \( \lambda=\frac{h}{mc}\) can be derived from my equations. From my equation \( E=mc^2=hf=Iw^2k_2=Lwk_2\) . we can write \( hf=Lwk_2\) or \(hf=L2\pi fk_3k_2 \) or \( h=L2\pi k_3k_2\) . Now we can consider \( mc^2=Lwk_2\) or \(mc=\frac{Lwk_2}{c}=\frac{Lwk_2}{k_1rw}=\frac{Lk_2}{rk_1} \) . So we can write \( \lambda=\frac{h}{mc}=\frac{L2\pi k_3k_2}{\frac{Lk_2}{rk_1}}=r2\pi k_1k_3 \) . Here \(k_1 , k_2 , k_3 \) are constants. \(c=k_1rw\) , \( w=2\pi fk_3\) and \(L=Iw \) . From my equation of compton wavelength \(\lambda=\frac{h}{mc}=r2\pi k_1k_3 \) , we can see that compton wavelength is function of radius. \(\lambda=f(r)\) . Electron has compton wavelength. So, we can say it has non-zero radius.
From my equations classical electron radius \( r_e\) also can be related with its actual radius \( r\). https://en.wikipedia.org/wiki/Fine-structure_constant . As per the above link \( \alpha=\frac{r_e}{r_Q}\) and \(L=r_Qm_ec \) . From my equations earlier we have seen that \( mc=\frac{Lk_2}{rk_1}\) or \( L=\frac{mcrk_1}{k_2}\) . Considering this a case for electron, \(m=m_e \) and we can write \( L=r_Qmc=\frac{mcrk_1}{k_2}\) . From this we can see \( r_Q=\frac{rk_1}{k_2}\) . Putting this value in the first equation, we can write \( \alpha=\frac{r_e}{r_Q}=\frac{r_e}{\frac{rk_1}{k_2}}\) or \(r_e=\frac{\alpha rk_1}{k_2} \) . From this we can see that \(r_e=f(r) \) . From this also we can conclude that electron radius \( r\) is non zero.
And now please explain how an anonymous user posting an unsourced statement on Wikipedia was enough to convince you of its truth. So how do you resolve the incompatibility with the premises of the theory of relativity?
Wikipedia is read by lot of people world over. Anybody can find any anomaly. If you have observed any anomaly, you can point out. It is user friendly and easy reference. I think, I already explained earlier that Lorentz Transformations are basically quantum phenomena.
If you don't want to answer the question, just say so. So you have no idea how to resolve the incompatibilities. Also, in your first derivation, by assuming \(L\) to be non-zero, you've assumed that the electron has a non-zero radius; that's how the definition of angular momentum works. Your entire calculation is thus circular reasoning. And this is in fact explicitly stated in the exact section of the fine-structure constant you are referring to. So for your second derivation, you are also assuming a non-zero radius to derive a non-zero radius: circular reasoning. How do you resolve that circular reasoning?
In the academia, I observed that \( k_1k_3=\frac{1}{4}\) . With this value you can check proton compton wavelength from my equation. It is coming very close.
Electron compton wavelength is known. Considering \(k_1k_3=\frac{1}{4} \) , a very close value for electron radius can be known.
https://physics.nist.gov/cgi-bin/cuu/Value?pcomwlbar|search_for=compton ; https://en.wikipedia.org/wiki/Proton . From these two sites \( r_p \simeq 0.84 fm\) and \( \lambda \simeq 0.21 fm\) . The ratio is very close to \(\frac{1}{4} \) .
My equations are general equations which should be true for all the massive spinning particles. Applying these equations for electron is only one of the cases.
Please give your definition of \(L\), and demonstrate that this definition makes sense for particles with zero radius.
https://physics.nist.gov/cgi-bin/cuu/Value?ncomwlbar ; Neutron compton wavelength over 2 pi is about 0.21 fm. https://en.wikipedia.org/wiki/Neutron ; Neutron radius is about 0.8 fm. Here also my equation for compton wavelength is very close.
So you admit that your definition of \(L\) excludes the possibility of a zero-radius particle spinning by definition. Because \(L=I\omega\), where \(I=mr^2k\), which is \(0\) when \(r=0\). In other words, with your definition, a zero-radius particle cannot be spinning. And since you model an electron as a spinning particle, you've implicitly assumed an electron has a non-zero radius. Conclusion, your derivation is circular reasoning.
Considering \(k_1k_3=\frac{1}{4} \), my equation for compton wavelength can be rewritten as \(\lambda=\frac{h}{mc}=r2\pi k_1k_3=\frac{r\pi}{2} \)