spin

**spin geometry**, **string geometry**, **fivebrane geometry**

The **spin** of a particle in quantum mechanics/quantum field theory is its intrinsic angular momentum, but subject to the possibility that the particle may be a fermion so that that its angular momentum is not determined by the representation theory of the special orthogonal group, but of the spin group.

By the spin-statistics theorem, the spin of any elementary particle must be (in magnitude) half of an integer multiple of Planck's constant ($\hbar = h/2\pi$), an integer if the particle is a boson but only a half-integer if the particle is a fermion.

Revised on October 4, 2013 01:14:53
by Urs Schreiber
(82.169.114.243)