Helicity topological quantization

It is only on this level that the link between helicity and topological quantization [103] can be understood properly. The 0(3) group, like the U(l) group, is multiply connected. The group space of U(l) is a circle [6, p. 105]. As explained earlier in this review, this is not simply connected because a path that goes twice... 

In the previous section, it was shown that the constant a must be equal to [hc in order to obtain the right quantization of the electromagnetic helicity. This implies that the topological model predicts that the fundamental charge, either electric or magnetic, has the value... 

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