Representation of coherent states in the theory of many-boson systems

Masahiko Tsujii, Toshiyuki Nishiyama

The ground-state energy of a many-boson system is obtained by the aid of a coherent-state representation in the high densigy limit. Dealing with the problem in a lattice space, some difficulties encountered in previous collective variable theories have been overcome. In particular, it is shown that Fröhlich's objection about the non-existence of the canonical conjugate to the density is not fatal to the previous theory of the density and phase operator approach. The ground-state energy obtained have agrees with that given by Brueckner and Lee.

F. Rocca

Richard David Etters

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.

James S. Langer

It is shown that the coherent-state representation of a many-boson wave function may be identified with the order-parameter function conventionally used to describe a superfluid. The statistical mechanics of the many-boson system is reformulated in terms of the coherent states, and a theory of the Ginzburg-Landau form is recovered in an obvious approximation. The formalism is particularly useful for describing metastable states of finite superflow and the fluctuations which may cause spontaneous decay of such states.

Richard David Etters