Cartan subalgebra
Let be a Lie algebra. Then a Cartan subalgebra
is a maximal subalgebra
of which is self-normalizing, that is, if for all , then as well. Any Cartan subalgebra is nilpotent
, and if is semi-simple
, it is abelian
. All Cartan subalgebras of a Lie algebra are conjugate by the adjoint action of any Lie group with algebra .
The dimension of is called the rank of .