[Outline of how notion of deforming symmetries back to identity more fundamental than merely looking like the identity in a naive transformation; thus to universal cover. Mention of 2D case. Demonstration that SO(3) is not simply connected. Demonstration that SU(2) is the universal cover of SO(3).]

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Spin Quantization, Double Covers and the Dirac Cup Trick

An outline of the subtleties which can arise in applying representation theory to non-simply-connected Lie groups

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