A. Orlowski et A. Strasburger, A GENERALIZATION OF THE CONSTRUCTION OF THE CLASS OPERATOR, Journal of physics. A, mathematical and general, 27(1), 1994, pp. 167-175
It is shown that the construction of the class operator for SU(2) is a
partial case of a much more general problem, that of decomposing an o
perator into components transforming under conjugation according to a
given irreducible representation. The problem is solved generally for
arbitrary compact groups and some possibilities for extensions of this
procedure to the case of non-compact groups are indicated.