An operator
 |
on a representation 
of a Lie algebra.
Casimir Operator
See also
Lie AlgebraExplore with Wolfram|Alpha
References
Jacobson, N. Lie Algebras. New York: Dover, p. 78, 1979.Referenced on Wolfram|Alpha
Casimir OperatorCite this as:
Weisstein, Eric W. "Casimir Operator." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/CasimirOperator.html