Bosonic Systems

Walter E Thirring

A. Kuriyama, Constança Providência, João da Providência +1 more

As preparation for extending a new boson realization in the Lipkin model, recently proposed by the present authors, a possible boson realization for a many-boson system is developed. The basic idea comes from the MYT boson mapping method. In order to obtain the classical counterpart to the quantal system in this new boson realization, a certain wave packet is used.

Cheng-Li Wu, D.H. Feng, Jin-Quan Chen +1 more

An effective boson Hamiltonian is derived from the original Hamiltonian of a many-fermion system. The results show that when the intrinsic motion of bosons is collective and the excitation energies of the system are small, the effective boson-boson interaction can be reduced to a two-body interaction while for odd systems or systems with uncorrelated fermions, there is an additional two-body boson-fermion interaction. Both these interactions can be calculated from the original fermion-fermion ones. Thus, the microscopic foundation of the interacting boson model is established without recourse to mapping procedures.NUCLEAR STRUCTURE Interacting boson model, boson fermion hybrid representation, microscopic foundation.

Alan D. Sokal

A. Kuriyama, João da Providência, Y. Tsue +1 more

With the aim of obtaining the classical counterpart of the su(2)-spin system and its quantal fluctuations in the frame of the boson coherent state, the Holstein-Primakoff and Marumori-Yamamura-Tokunaga boson expansions are investigated. The starting point is found in the Schwinger boson representation for the su(2)-spin system and its reformation. Dirac's canonical theory for constraint systems is also applied to the su(2)-spin system. In conclusion, the latter boson expansion is found to be superior to the former with respect to the use of the boson coherent state.