Coupled-cluster theory for systems of bosons in external traps
- Theoretische Chemie, Physikalisch-Chemisches Institut, Universitaet Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg (Germany)
A coupled-cluster approach for systems of N bosons in external traps is developed. In the coupled-cluster approach the exact many-body wave function is obtained by applying an exponential operator exp{l_brace}T{r_brace} to the ground configuration [{phi}{sub 0}>. The natural ground configuration for bosons is, of course, when all reside in a single orbital. Because of this simple structure of [{phi}{sub 0}>, the appearance of excitation operators T={sigma}{sub n=1}{sup N}T{sub n} for bosons is much simpler than for fermions. We can treat very large numbers of bosons with coupled-cluster expansions. In a substantial part of this work, we address the issue of size consistency for bosons and enquire whether truncated coupled-cluster expansions are size consistent. We show that, in contrast to the familiar situation for fermions for which coupled-cluster expansions are size consistent, for bosons the answer to this question depends on the choice of ground configuration. Utilizing the natural ground configuration, working equations for the truncated coupled-cluster with T=T{sub 1}+T{sub 2}, i.e., coupled-cluster singles doubles are explicitly derived. Finally, an illustrative numerical example for a condensate with up to N=10 000 bosons in an harmonic trap is provided and analyzed. The results are highly promising.
- OSTI ID:
- 20787144
- Journal Information:
- Physical Review. A, Vol. 73, Issue 4; Other Information: DOI: 10.1103/PhysRevA.73.043609; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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