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advanced_tools:topology:cocycles [2017/12/20 10:35] jakobadmin [Why is it interesting?] |
advanced_tools:topology:cocycles [2017/12/20 10:35] (current) jakobadmin [Student] |
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- | Because state vectors differing only by a phase are the same for certain purposes, it turns out that symmetries need not correspond to unitary representations; they can correspond to [[group_theory:notions:projective_representation|projective representations]], in which the rules of a representation hold only 'up to phases': | + | Because state vectors differing only by a phase are the same for certain purposes, it turns out that symmetries need not correspond to unitary representations; they can correspond to [[advanced_tools:group_theory:representation_theory:projective_representation|projective representations,]] in which the rules of a representation hold only 'up to phases': |
$$ \rho(1) = e^{i\theta}, $$ | $$ \rho(1) = e^{i\theta}, $$ |