Microscopic foundation for the particle-vibrator model

The tools for deriving microscopically the particle-vibrator model are presented in the form of a new fermion-boson expansion in which valence particles or holes added to a closed shell are treated essentially as fermion degrees of freedom, while particle-hole excitations of the closed shell are treated as bosons. The Pauli principle is completely fulfilled without redundancy Both the nonunitary (Dyson) and unitary representation are given. (orig.)