Theory of elementary excitations in unstable Bose-Einstein condensates

U. Leonhardt, T. Kiss, P. Ohberg

Research output: Contribution to journalArticlepeer-review

51 Citations (Scopus)
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Like classical fluids, quantum gases may suffer from hydrodynamic instabilities. Our paper develops a quantum version of the classical stability analysis in fluids, the Bogoliubov theory of elementary excitations in unstable Bose-Einstein condensates. In unstable condensates the excitation modes have complex frequencies. We derive the normalization conditions for unstable modes such that they can serve in a mode decomposition of the noncondensed component. Furthermore, we develop approximative techniques to determine the spectrum and the mode functions. Finally, we apply our theory to sonic horizons - sonic black and white holes. For sonic white holes the spectrum of unstable modes turns out to be intrinsically discrete, whereas black holes may be stable.
Original languageEnglish
Number of pages11
JournalPhysical Review A
Issue number3
Publication statusPublished - 11 Mar 2003


  • soft condensed matter
  • bose-einstein
  • fluids
  • physics


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