On one hand, in reading Georgi's book in group theory, I comprehend the invariant tensor as a special "tensor", which is unchanged under the action of any generators. On the other hand, CG decomposition is to decompose the product of two irreps into different irreps.(adsbygoogle = window.adsbygoogle || []).push({});

Now it is claimed that invariant tensors are Clebsch-Gordan coupling constants for the product of two irreps. Why?

Thank you very much for your answer!

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# Why are invariant tensors also Clebsch-Gordan coefficients?

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