Infrared Divergence of the Angular Momentum of Bremsstrahlung and the Physical Structure of the Electron
In a private communication, Biedenharn pointed out that the statistical independence of photon emission in the infrared limit in a bremsstrahlung scattering process may lead to a logarithmically divergent angular momentum for the radiated photons and the scattering system. It is shown that the expectation values of these angular momentum vectors are free of infrared divergence, but the expectation values of their squares are infinite due to an infrared divergence. The physical significance of this result is that an incident electron of arbitrarily large impact parameter can scatter from a finite range potential. This may be ascribed to the physical structure of the electron, namely its photon cloud.