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  Is the electron-g-factor related to Dirac's string trick?

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The internet is full of accounts and videos telling how Dirac's string trick explains the spin 1/2 of the electron. Dirac used the string trick in his lectures to explain the properties of electron spin.

Does Dirac's string trick also explain the g-factor value g=2, thus the difference to the classical / orbital value g=1?

A longer search in libraries, Google Scholar and normal Google did not yield anything.

asked Dec 21, 2019 in Open problems by Whirl [ revision history ]
edited Dec 21, 2019

Dirac's string trick leads to spin 1/2 of what?

But Dirac's string trick (experiment) is not made with electron!

Correct, he did it with a pair of scissors. But he explained the electron with it.

First, the "rotation" to $4\pi$ is not equivalent to "no rotation at all". One needs some other "actions" to return to the "no rotation" state. And these "other actions" are topologically equivalent to rotation to $-4\pi$.

1 Answer

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The string trick explains nothing at all about the electron. It just demonstrates that SO(3) has a double covering, and thus permits unitary representations with half-integral spin. There is no relation with any Hamiltonian, let alone a particular interaction strength.

answered Dec 26, 2019 by Arnold Neumaier (15,438 points) [ revision history ]
edited Dec 26, 2019 by Arnold Neumaier

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