446 research outputs found
Strong-Coupling Calculation of Fluctuation Pressure of a Membrane Between Walls
We calculate analytically the proportionality constant in the pressure law of
a membrane between parallel walls from the strong-coupling limit of variational
perturbation theory up to third order. Extrapolating the zeroth to third
approximations to infinity yields the pressure constant alpha=0.0797149. This
result lies well within the error bounds of the most accurate available
Monte-Carlo result 0.0798 +- 0.0003.Comment: Author Information under
http://www.physik.fu-berlin.de/~kleinert/institution.html . Latest update of
paper also at http://www.physik.fu-berlin.de/~kleinert/28
Systematic Semiclassical Expansion for Harmonically Trapped Ideal Bose Gases
Using a field-theoretic approach, we systematically generalize the usual
semiclassical approximation for a harmonically trapped ideal Bose gas in such a
way that its range of applicability is essentially extended. With this we can
analytically calculate thermodynamic properties even for small particle
numbers. In particular, it now becomes possible to determine the critical
temperature as well as the temperature dependence of both heat capacity and
condensate fraction in low-dimensional traps, where the standard semiclassical
approximation is not even applicable.Comment: Author Information under
http://www.theo-phys.uni-essen.de/tp/ags/pelster_di
Quantum Fluctuations in Dipolar Bose Gases
We investigate the influence of quantum fluctuations upon dipolar Bose gases
by means of the Bogoliubov-de Gennes theory. Thereby, we make use of the local
density approximation to evaluate the dipolar exchange interaction between the
condensate and the excited particles. This allows to obtain the Bogoliubov
spectrum analytically in the limit of large particle numbers. After discussing
the condensate depletion and the ground-state energy correction, we derive
quantum corrected equations of motion for harmonically trapped dipolar Bose
gases by using superfluid hydrodynamics. These equations are subsequently
applied to analyze the equilibrium configuration, the low-lying oscillation
frequencies, and the time-of-flight dynamics. We find that both atomic magnetic
and molecular electric dipolar systems offer promising scenarios for detecting
beyond mean-field effects.Comment: Published in PR
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