A Completeness relation for SO(N)

  • A
  • Thread starter Thread starter Einj
  • Start date Start date
  • Tags Tags
    Relation
AI Thread Summary
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.
Einj
Messages
464
Reaction score
59
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!
 
Mathematics news on Phys.org
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.
 
Last edited by a moderator:
  • Like
Likes Einj
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.
 
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. In Dirac’s Principles of Quantum Mechanics published in 1930 he introduced a “convenient notation” he referred to as a “delta function” which he treated as a continuum analog to the discrete Kronecker delta. The Kronecker delta is simply the indexed components of the identity operator in matrix algebra Source: https://www.physicsforums.com/insights/what-exactly-is-diracs-delta-function/ by...
Suppose ,instead of the usual x,y coordinate system with an I basis vector along the x -axis and a corresponding j basis vector along the y-axis we instead have a different pair of basis vectors ,call them e and f along their respective axes. I have seen that this is an important subject in maths My question is what physical applications does such a model apply to? I am asking here because I have devoted quite a lot of time in the past to understanding convectors and the dual...
Back
Top