This quantity is mapped to boson creation and annihilation operators by a transformation due to Holstein and Primakoff. Because the group of Lorentz transformations is non-compact, in one case, one introduces Dirac spinors to apply Lorentz transformations to this quantity. Waves of this quantity are described by dispersion relations of magnons and phonons and occur in ferromagnets. According to a 
This quantity is mapped to boson creation and annihilation operators by a transformation due to Holstein and Primakoff. Because the group of Lorentz transformations is non-compact, in one case, one introduces Dirac spinors to apply Lorentz transformations to this quantity. Waves of this quantity are described by dispersion relations of magnons and phonons and occur in ferromagnets. According to a result, which holds for all Lorentz invariant field theories on a positively normed Hilbert space, this quantity dictates whether the wave function is symmetric or antisymmetric under exchange. That statement is this quantity's "statistics theorem," and its quantization was demonstrated by the Stern-Gerlach experiment. This degree of freedom permits two electrons to occupy each orbital and is either integer or half-integer for bosons and fermions. For 10 points, name this intrinsic form of angular momentum.
This quantity is mapped to boson creation and annihilation operators by a transformation due to Holstein and Primakoff.
spin angular momentum [prompt on angular momentum; do not accept or prompt on "momentum"]