Nuclear shape: meaning and limitations
The interpretation of nuclear observables in the laboratory frame in terms of the intrinsic deformation parameters beta and gamma is a classical theme in nuclear structure. Here we use Kumar's quadrupole invariants to clarify the meaning and limitations of assigning definite values to these intrinsic parameters. In particular, we find that the parameter $\beta$ often has a non-negligible degree of softness, and that the angle $\gamma$ is usually characterized by large fluctuations, rendering its effective value not meaningful.