An interpretation of Casimir operators of the U(6/12) group

An interpretation is presented of the Usup(B+F)(6) Casimir operator which appears in a group theoretical description of the U(6/12) dynamical bosonfermion symmetry. The Usup(B+F)(6) term is shown to be equivalent to a very specific choice of the exchange term in the genral hamiltonian of the interacting boson-fermion model. The analysis also suggests the possible importance of additional exchange terms in the hamiltonian which have so far been neglected. (orig.)