The Wielandt subalgebra of a Lie algebra (with D. Barnes), J.
Aust. Math. Soc. 74 (2003), 313-330.
Following the analogy with group theory, we define the
Wielandt subalgebra of a finite-dimensional Lie algebra to be the
intersection of the normalisers of the subnormal subalgebras. In a
non-zero algebra,this is a non-zero ideal if the ground field has
characteristic 0 or if the derived algebra is nilpotent, allowing the
definition of the Wielandt series. For a Lie algebra with nilpotent
derived algebra, we obtain a bound for the derived length in terms of the
Wielandt length and show this bound to be best possible. We also
characterise the Lie algebras with nilpotent derived algebra and Wielandt