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DOI 10.5286/raltr.2010017
Persistent URL http://purl.org/net/epubs/work/53447
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Record Id 53447
Title Temperature dependence of the physical properties of Bose-Einstein condensed gases and liquids
Abstract Gases and liquids in the presence of Bose-Einstein condensation (BEC) have unique and very striking macroscopic physical properties. For example they exhibit flow without viscosity, quantised vortices and two-fluid behaviour. Macroscopic quantum interference effects in the form of density oscillations are observed when two or more clouds of ultra-cold Bose-Einstein condensed atoms overlap. The microscopic properties of Bose-Einstein condensed liquid (superscript)4He are also uniquely anomalous and unexplained. Neutron and X-ray scattering measurements show that liquid (superscript)4He in its superfluid phase is the only known liquid in which pair correlations between atomic positions decrease upon cooling. The liquid also shows an anomalous thermal expansion upon cooling. Inelastic neutron scattering shows that it is also the only known liquid which has sharp peaks in its dynamic structure factor. It is shown here that all the above phenomena can be explained in a physically transparent and quantitative way by simply stated postulates. The first is that in the presence of BEC at finite temperature, the many particle wave functions of occupied states can be written as the sum of a componant which is localized in coordinate space and a component which is delocalized. The second is that the delocalised component is identical to the ground state wave function. It is argued that these postulates are in fact forced by basic quantum mechanics, existing theoretical treatments of BEC and a wide range of experimental measurements of Bose-Einstein condensed liquid (superscript)4He.
Organisation ISIS , STFC
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Related Research Object(s): 12317519
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Language English (EN)
Type Details URI(s) Local file(s) Year
Report RAL Technical Reports RAL-TR-2010-017. 2010. RALTR-2010-017.pdf 2010