= Particle polarization
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A particle polarization specifies a physical spin state at fixed <four-momentum>. Massive spin states transform under the rotation <little group> $SO(D-1)$; finite-spin massless states transform under its transverse rotation part $SO(D-2)$. A <massive two-form field> has $\binom{D-1}{2}$ such states, while a <two-form gauge field> has $\binom{D-2}{2}$. Polarization components must be counted after field equations and any gauge equivalence are imposed.
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