Friday, October 11, 2019

What is the bare charge of an electron?

The scattering experiment in our previous blog post can be interpreted as a way to measure the electric repulsion between two electrons, and therefore, their charge.

Some people think that the electron is surrounded by a cloud of virtual electron-positron pairs which screen part of the negative bare charge of the electron. For an unknown reason, there is less screening if real electrons come close to each other. That would explain the stronger coupling constant. But this does not help much because we have to refer to an "unknown reason".

We in this blog have the philosophy that only measurable quanta exist as "particles" and the rest is classical fields which obey classical field equations.

We do not know the correct QED lagrangian. Let us assume that Feynman diagrams indirectly describe the lagrangian correctly, whatever it is.

The trigger to create a virtual pair in the one-loop Feynman diagram is the exchange of the large momentum virtual photon between the colliding electrons.

The reaction in the electron field is to the momentum exchange. That suggests that the reaction is a dynamic phenomenon.

Suppose that we somehow attach two electrons very close to each other. They exchange a lot of momentum in a second. Is there a similar virtual pair loop present in this case?

We need to analyze the Feynman formulas for the loop. What kind of a reaction do the formulas describe in the electron field?

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