Three Forms of Boson Expansions for the su(2)-Spin System and Their c-Number Counterparts

Abstract

In the framework of the Marumori-Yamamura-Tokunaga boson expansion, three forms for the su(2)-spin system are presented. The first is related with the well-known Holstein-Primakoff boson expansion and the second is the expansion reinvestigated in a previous paper by the present authors. The third is, in some sense, the original part of this paper. Corresponding with three forms, c-number counterparts are obtained by using three forms of wave packets defined in the su(2)-spin space. With the help of appropriate quantization rule, they go back to the original boson expansions. Furthermore, it is discussed if the c-number counterparts can be regarded as the classical counterparts. Finally, the relation to the su(1, 1)-algebraic model is discussed.