[GAP Forum] Casimir operator of a Lie algebra

[Stefano Simonucci]

Dear GAP Forum,
    I have the following problem, i.e. to find the Casimir's operators 
of the Lie ALgebra SO(n) and SU(n).
But I realized that it isn't possible to find the center of an
Universal Enveloping Algebra with GAP.
For example:

gap> L:= SimpleLieAlgebra( "A", 1, Rationals );
<Lie algebra of dimension 3 over Rationals>
gap> UL:= UniversalEnvelopingAlgebra( L );
<algebra-with-one of dimension infinity over Rationals>
gap> Center(UL);
Error, this case will eventually be handled by the Vector Enumerator
which is not available yet called from
OperationAlgebraHomomorphism( A, [ [ Zero( A ) ] ], OnRight ) called from
IsomorphismMatrixFLMLOR( A ) called from
IsFiniteDimensional( A ) called from
<function>( <arguments> ) called from read-eval-loop
Entering break read-eval-print loop ...
you can 'quit;' to quit to outer loop, or
you can 'return;' to continue

Do you know another method.
Thanks

Stefano