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 | | A principal three-dimensional subalgebra of $G_l$ is a subalgebra $A$ of type ${\rm sl}(2)$, with basis $\{E,F,H\}$ satisfying \beq [H,E]=2E,\qquad [H,F]=-2F,\qquad [E,F]=H, \eeq such that the number of irreducible components occurring in the complete reduction of the adjoint representation of $G_l$ with respect to $A$ is equal to $l$ (Kostand 1959). |
 | | In this Letter the investigation of principal subalgebras of quantum enveloping algebras of type ${\rm gl}_q(l+1)$ or ${\rm sl}_q(l+1)$ is initiated. |
 | | A principal subalgebra of ${\rm gl}_q(l+1)$ is defined as follows~: it is a subalgebra of ${\rm gl}_q(l+1)$ of type ${\rm sl}_q(2)$, i.e.~its generators $\{E,F,H\}$ satisfy \beq [H,E]=2E,\qquad [H,F]=-2F,\qquad [E,F]=[H], \label{5} \eeq and in the limit $q\rightarrow q$, this ${\rm sl}_q(2)$ subalgebra reduces to the principal subalgebra of ${\rm gl}(l+1)$. |
| allserv.rug.ac.be /~jvdjeugt/files/tex/q-princ.tex (1831 words) |
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