Abstract:
We show that the Inoenue-Wigner contraction naturally associated
to a reduction chain $\frak{s}\supset \frak{s'}$ of
semisimple Lie algebras induces a decomposition of the Casimir
operators into homogeneous polynomials, the terms of which can be
used to obtain additional mutually commuting missing label
operators for this reduction. The adjunction of these scalars that
are no more invariants of the contraction allow to solve the
missing label problem for those reductions where the contraction
provides an insufficient number of labelling operators.