Poetry of Physics and the Physics of Poetry

222 The Poetry of Physics and The Physics of Poetry

probable. Nevertheless, these small corrections have been calculated and
have been shown to agree with experiment as pointed out above. In
addition to the diagrams in which two photons are exchanged between
the charged particles, there are other two-photon diagrams in which only
one photon is exchanged. We give three examples of these types of
diagrams, Fig. 22.3:

Quantum Electrodynamics 213

one photon is exchanged. We give three examples of these types of

diagrams, Fig. 22.3:

In the first diagram (Fig. 22.3) the electron emits and absorbs a

photon before exchanging the photon with the other charged particle.

This type of diagram does change the nature of the electric interaction

but it does not change the mass of the charged particle. The second

diagram also does not change the nature of the electric force but it does

affect the strength of the particle’s charge. The third diagram involves

the creation of a virtual electron-antielectron pair from the virtual

photon. This diagram gives rise to a correction of the electron’s magnetic

moment.

We shall conclude our discussion of quantum electrodynamics by

presenting the Feynman diagrams representing pair creation and pair

annihilation. For pair creation, the presence of a nucleus is necessary in

order to conserve energy and momentum. We shall represent the nucleus

by the symbol Z in our diagram, Fig. 22.4, and the scattered nucleus by

Z’. In the process of creation we see a real photon and a nucleus entering.

The real photon turns into an electron positron pair. The electron then

exchanges a virtual photon with the nucleus.

Fig. 22.4 Electron-positron pair creation reaction

Fig. 22.3 Two photon diagrams where only a single photon is exchanged.

In the first diagram (Fig. 22.3) the electron emits and absorbs a
photon before exchanging the photon with the other charged particle.
This type of diagram does change the nature of the electric interaction
but it does not change the mass of the charged particle. The second
diagram also does not change the nature of the electric force but it does
affect the strength of the particle’s charge. The third diagram involves
the creation of a virtual electron-antielectron pair from the virtual
photon. This diagram gives rise to a correction of the electron’s magnetic
moment.
We shall conclude our discussion of quantum electrodynamics by
presenting the Feynman diagrams representing pair creation and pair
annihilation. For pair creation, the presence of a nucleus is necessary in
order to conserve energy and momentum. We shall represent the nucleus
by the symbol Z in our diagram, Fig. 22.4, and the scattered nucleus by
Z′. In the process of creation we see a real photon and a nucleus entering.

Quantum Electrodynamics 213

one photon is exchanged. We give three examples of these types of

diagrams, Fig. 22.3:

Fig 22.3 Two photon diagrams where only a single photon is exchanged

In the first diagram (Fig. 22.3) the electron emits and absorbs a

photon before exchanging the photon with the other charged particle.

This type of diagram does change the nature of the electric interaction

but it does not change the mass of the charged particle. The second

diagram also does not change the nature of the electric force but it does

affect the strength of the particle’s charge. The th ird diagram involves

the creation of a virtual electron-antielectron pair from the virtual

photon. This diagram gives rise to a correction of the electron’s magnetic

moment.

We shall conclude our discussion of quantum electrodynamics by

presenting the Feynman diagrams representing pair creation and pair

annihilation. For pair creation, the presence of a nucleus is necessary in

order to conserve energy and momentum. We shall represent the nucleus

by the symbol Z in our diagram, Fig. 22.4, and the scattered nucleus by

Z’. In the process of creation we see a real photon and a nucleus entering.

The real photon turns into an electron positron pair. The electron then

exchanges a virtual photon with the nucleus.

Fig. 22.4 Electron-positron pair creation reaction

Fig. 22.4 Electron-positron pair creation reaction.