Casimir Invariant

In mathematics, a Casimir invariant or Casimir operator is a distinguished element of the centre of the universal enveloping algebra of a Lie algebra. A prototypical example is the squared angular momentum operator, which is a Casimir invariant of the three-dimensional rotation group.

The Casimir invariant is named after Hendrik Casimir, who identified them in his description of rigid body dynamics in 1931.