CH110 Study Guide - Final Guide: Quantum Electrodynamics, Feynman Diagram, Vacuum Polarization
Quantum electrodynamics studies also processes
referred to as photon-photon interactions. As long as
the quantum electrodynamical photon is a wave, the
photon-photon interaction is in fact an interaction of
electromagnetic waves. The Maxwell equations are
linear and cannot describe this interaction. The
electromagnetic waves, however, polarize the vacuum
(see the end of Sec. 6) and interact via the vacuum
polarization. In this connection let us discuss Feynman
diagrams. A Feynman diagram is a schematic and
pictorial representation of an involved mathematical
formula that contains electromagnetic potentials and
electron-positron wavefunctions. There is nothing
peculiar to a particle-like photon in the formula.
Consequently, the photonic lines in the diagram should
be regarded as lines relevant to electromagnetic waves.
It will be recalled that the electromagnetic energy
portion hω
possesses a momentum p = hk ascribed customarily to
a photon (see the discussion of the Compton effect in
Sec. 5).
Of interest is to discuss the process termed the creation
of an electron-positron pair by a photon. The energy of
the pair is 2mc2. Replacing En − Em in (4.3) by 2mc2
yields
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Document Summary
Quantum electrodynamics studies also processes referred to as photon-photon interactions. As long as the quantum electrodynamical photon is a wave, the photon-photon interaction is in fact an interaction of electromagnetic waves. The maxwell equations are linear and cannot describe this interaction. The electromagnetic waves, however, polarize the vacuum (see the end of sec. In this connection let us discuss feynman diagrams. A feynman diagram is a schematic and pictorial representation of an involved mathematical formula that contains electromagnetic potentials and electron-positron wavefunctions. There is nothing peculiar to a particle-like photon in the formula. Consequently, the photonic lines in the diagram should be regarded as lines relevant to electromagnetic waves. It will be recalled that the electromagnetic energy possesses a momentum p = hk ascribed customarily to a photon (see the discussion of the compton effect in. Of interest is to discuss the process termed the creation of an electron-positron pair by a photon.
