Variational Approximation to the Non-Hermitian Dyson Boson Hamiltonian

Abstract

Boson expansion theories have recently generated a great deal of interest^1-5) as a convenient means for describing collective nuclear properties. Both unitary and nonunitary mappings have been used. The latter, referred to as the Dyson boson theory, has two advantages. It is exact and provides a finite boson expansion whereas the Hermitian theories are characterized by infinite boson expansions. However, some problems also arise. Due to the nonunitary nature of the Dyson mapping the normalization condition is not sufficient to normalize bra and ket vectors separately^5-7).