Simulations of thermal Bose fields in the classical limit

M. J. Davis, S. A. Morgan, and K. Burnett
Phys. Rev. A 66, 053618 – Published 25 November 2002
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Abstract

We demonstrate that the time-dependent projected Gross-Pitaevskii equation (GPE) derived earlier [M. J. Davis, R. J. Ballagh, and K. Burnett, J. Phys. B 34, 4487 (2001)] can represent the highly occupied modes of a homogeneous, partially-condensed Bose gas. Contrary to the often held belief that the GPE is valid only at zero temperature, we find that this equation will evolve randomized initial wave functions to a state describing thermal equilibrium. In the case of small interaction strengths or low temperatures, our numerical results can be compared to the predictions of Bogoliubov theory and its perturbative extensions. This demonstrates the validity of the GPE in these limits and allows us to assign a temperature to the simulations unambiguously. However, the GPE method is nonperturbative, and we believe it can be used to describe the thermal properties of a Bose gas even when Bogoliubov theory fails. We suggest a different technique to measure the temperature of our simulations in these circumstances. Using this approach we determine the dependence of the condensate fraction and specific heat on temperature for several interaction strengths, and observe the appearance of vortex networks. Interesting behavior near the critical point is observed and discussed.

  • Received 31 January 2002

DOI:https://doi.org/10.1103/PhysRevA.66.053618

©2002 American Physical Society

Authors & Affiliations

M. J. Davis1,2,*, S. A. Morgan2,3, and K. Burnett2

  • 1Department of Physics, University of Queensland, St Lucia, Queensland 4072, Australia
  • 2Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom
  • 3Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom

  • *Electronic address: mdavis@physics.uq.edu.au

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Issue

Vol. 66, Iss. 5 — November 2002

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