Definition of the shape parameter gamma in the interacting-boson model.

It is argued that any estimate of the shape parameter ..gamma.. determined from interacting-boson-model IBM wave functions depends on the choice of chi in the definition of the IBM quadrupole operator d/sub ..mu..//sup dagger/s+s/sup dagger/d-tilde/sub ..mu../+chi(d/sup dagger/d) /sub 2//sub ..mu../. The consequences of different choices are discussed.