TITLE: Tensoring Young Tableaus
QUESTION [2 upvotes]: As we all know very well, the finite dimensional irreducible representations of the compact Lie groups $SU(N)$ are labelled by Young tableaus. Now when we tensor two irreducible representations we get a sum of irreducibles, or equivalently, a collection of Young tableaus. Is there i visual way to see how tensoring tableaus works?

REPLY [1 votes]: The rule for tensoring irreps of U(N) -- or equivalently decomposing the product of Schur functions as a sum of Schur functions --- is known as the Littlewood-Richardson rule.  The modification for SU(N) is easy.The L-R rule  is algorithmic rather than visual though and is not easy to describe in a paragraph or two.  Further, hand calculations for anything other than small tableaux are tedious and  prone to error. There are websites and software packages that will do the job for you.
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