SPURIOUS STATES IN BOSON CALCULATIONS - SPECTER OR REALITY

We discuss some prevailing misconceptions about the possibility that s purious states may in general contaminate boson calculations of fermio n systems on either the phenomenological or microscopic level. Amongst other things we point out that the possible appearance of spurious st ates is not inherently a mapping problem, but rather linked to a choic e of basis in the boson Fock space. This choice is mostly dictated by convenience or the aim to make direct contact with phenomenology. Furt hermore, neither well established collectivity, nor the construction o f boson operators in the Marumori or OAI fashion can as such serve as a guarantee against the appearance of spurious boson states. Within an SO(12) generalisation of the Ginocchio model where collective decoupl ing is complete, we illustrate how spurious states may appear in an IB M-type sdg-boson analysis. We also show how these states may be identi fied on the boson level. This enables us to present an example of an s dg-spectrum which, although it may be reasonably correlated with exper imental data, nevertheless has the first few low lying states all spur ious when interpreted from the microscopic point of view. We briefly s peculate about the possibility that certain types of truncation may in fact automatically circumvent the appearance of spurious states.