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Author Griffin, A.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword PHYSICS ♦ BOSE-EINSTEIN CONDENSATION ♦ HARTREE-FOCK-BOGOLYUBOV THEORY ♦ EXCITATION FUNCTIONS ♦ EQUATIONS OF MOTION ♦ EXCITED STATES ♦ SPECTRA ♦ RESPONSE FUNCTIONS ♦ CONSERVATION LAWS
Abstract We derive and discuss the equations of motion for the condensate and its fluctuations for a dilute, weakly interacting Bose gas in an external potential within the self-consistent Hartree-Fock-Bogoliubov (HFB) approximation. Account is taken of the depletion of the condensate and the anomalous Bose correlations, which are important at finite temperatures. We give a critical analysis of the self-consistent HFB approximation in terms of the Hohenberg-Martin classification of approximations (conserving vs gapless) and point out that the Popov approximation to the full HFB gives a gapless single-particle spectrum at all temperatures. The Beliaev second-order approximation is discussed as the spectrum generated by functional differentiation of the HFB single-particle Green{close_quote}s function. We emphasize that the problem of determining the excitation spectrum of a Bose-condensed gas (homogeneous or inhomogeneous) is difficult because of the need to satisfy several different constraints. {copyright} {ital 1996 The American Physical Society.}
ISSN 01631829
Educational Use Research
Learning Resource Type Article
Publisher Date 1996-04-01
Publisher Place United States
Journal Physical Review, B: Condensed Matter
Volume Number 53
Issue Number 14


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