Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

For fun I began reading an interesting online paper I found, Spiders for rank 2 Lie algebras, and on page $5$ we have the following calculation, akin to a tensor product expansion via bilinearity:

$\hskip 0.8in$ 21

However, I believe the $21=6+6+9$ should just be a $12=6+6$, so that $9$ appears only once in the final result as the coefficient of the second web you see. What's going on?

(Also, help on more pertinent tags would be appreciated.)

share|cite|improve this question
Do you propose a 'spider' tag? – Isaac Solomon Nov 15 '12 at 6:01
up vote 3 down vote accepted

Yes, you are right. I think the fact that $21=6+6+9$ is a coincidence; I think it is more likely that Prof. Kuperberg transposed the digits $1$ and $2$.

share|cite|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.