Vacuum polarization

In quantum field theory, and specifically quantum electrodynamics, vacuum polarization describes a process in which a background electromagnetic field produces virtual electron–positron pairs that change the distribution of charges and currents that generated the original electromagnetic field. It is also sometimes referred to as the self-energy of the gauge boson (photon).

The effects of vacuum polarization were first observed experimentally prior to 1947 before they were theoretically calculated (by Hans Bethe on the return train ride from the Shelter Island Conference to Cornell) after developments in radar equipment for World War II resulted in higher accuracy for measuring the energy levels of the hydrogen atom (the Lamb shift) and the anomalous magnetic dipole moment of the electron (corresponding to the deviation from the Dirac equation predicted value of 2 of the spectroscopic electron g-factor value), measured by I.I. Rabi.

The effects of vacuum polarization have been routinely observed experimentally since then as very well understood background effects. Vacuum polarization referred to below as the one loop contribution occurs with leptons (electron-positron pairs) or quarks, the former (leptons) first observed in 1940s but also recently observed in 1997 using the TRISTAN particle accelerator in Japan, the latter (quarks) along with multiple quark-gluon loop contributions from the early 1970s to mid-1990s using the VEPP-2M particle accelerator at the Budker Institute of Nuclear Physics in Siberia in Russia and many other accelerator laboratories worldwide.

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