Effective action approach to a trapped Bose gas
2002 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 66, no 3, 033607-12 p p.Article in journal (Refereed) Published
The effective-action formalism is applied to a gas of bosons. The equations describing the condensate and the excitations are obtained using the loop expansion for the effective action. For a homogeneous gas, the expansion in terms of the diluteness parameter is identified in terms of the loop expansion. The loop expansion and the limits of validity of the well-known Bogoliubov [J. Phys. (Moscow) 11, 23 (1947)] and Popov, (Zh. Éksp. Teor. Fiz. 47, 1759 (1964) [Sov. Phys. JETP 20, 1185 (1965)]) equations are examined analytically for a homogeneous dilute Bose gas and numerically for a gas trapped in a harmonic-oscillator potential. The expansion to one-loop order, and hence the Bogoliubov equation, is shown to be valid for the zero-temperature trapped gas as long as the characteristic length of the trapping potential exceeds the s-wave scattering length.
Place, publisher, year, edition, pages
APS Physics , 2002. Vol. 66, no 3, 033607-12 p p.
Atom and Molecular Physics and Optics
IdentifiersURN: urn:nbn:se:umu:diva-40465DOI: 10.1103/PhysRevA.66.033607OAI: oai:DiVA.org:umu-40465DiVA: diva2:399758