Graduate Completeness relation for SO(N)

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The discussion focuses on the completeness relation for the fundamental representation of SO(N). Unlike SU(N), there is no direct analogue for SO(N), as highlighted by a reference to a paper by C. C. Nishi. Participants mention that the completeness relation can be derived using the definition of generators for SO(N), specifically through the structure constants of the algebra. The relation obtained shows that contracting the generators yields a specific form involving Kronecker deltas. The conversation concludes with a note that the situation becomes more complex in the spinor representation.
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Hello everyone,
I was wondering if anyone knows what the completeness relation for the fundamental representation of SO(N) is.
For example, in the SU(N) we know that, if T^a_{ij} are the generators of the fundamental representation then we have the following relation
$$
T^a_{ij}T^a_{km}=\frac{1}{2}\left(\delta_{im}\delta_{jk}-\frac{1}{N}\delta_{ij}\delta_{km}\right)
$$
This follows from the fact that the T^a, together with the identity form a complete basis for the N\times N complex matrices.

Does anyone know how to find the analogous for SO(N) (if any)?

Thanks a lot!
 
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There is not an analogue. See http://repositorio.unesp.br/bitstream/handle/11449/23433/WOS000234099500010.pdf?sequence=1 by C. C. Nishi
equation 22 and the paragraph following it.
 
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Einj said:
Hello everyone,
I was wondering if anyone knows what the completeness relation for the fundamental representation of SO(N) is.
For example, in the SU(N) we know that, if T^a_{ij} are the generators of the fundamental representation then we have the following relation
$$
T^a_{ij}T^a_{km}=\frac{1}{2}\left(\delta_{im}\delta_{jk}-\frac{1}{N}\delta_{ij}\delta_{km}\right)
$$
This follows from the fact that the T^a, together with the identity form a complete basis for the N\times N complex matrices.

Does anyone know how to find the analogous for SO(N) (if any)?

Thanks a lot!

Such a relation you can obtain in fundamental rep by yourself just using definition of generators
$$
(\lambda_{ab})_{cd}=-i(\delta_{ac}\delta_{bd}-\delta_{ad}\delta_{bc}) \in so(n).
$$
By contracting with an other $\lambda_{ab})_{$ you get
$$
(\lambda_{ab})_{cd}(\lambda_{ab})_{ef}=-2(\delta_{ce}\delta_{df}-\delta_{cf}\delta_{de}).
$$

In spinor rep it's going to be more complicated.
 
Here is a little puzzle from the book 100 Geometric Games by Pierre Berloquin. The side of a small square is one meter long and the side of a larger square one and a half meters long. One vertex of the large square is at the center of the small square. The side of the large square cuts two sides of the small square into one- third parts and two-thirds parts. What is the area where the squares overlap?

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