The centralizer of a set of vectors S in a subalgebra h is the subalgebra of vectors in h which commute with all the vectors in S.

Centralizer(S, h) calculates the centralizer of the set S in the subalgebra h.  If the second argument h is not specified then the default is h = g, and the centralizer of S in g is calculated.

A list of vectors defining a basis for the centralizer of S is returned.  If the centralizer of S is trivial, then an empty list is returned.

The command Centralizer is part of the DifferentialGeometry:-LieAlgebras package.  It can be used in the form Centralizer(...) only after executing the commands with(DifferentialGeometry) and with(LieAlgebras), but can always be used by executing DifferentialGeometry:-LieAlgebras:-Centralizer(...).