X iv : c on d - m at / 9 60 72 06 v 1 2 9 Ju l 1 99 6 Microscopic calculation of the phonon - roton branch in superfluid 4
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چکیده
Diffusion Monte Carlo results for the phonon-roton excitation branch in bulk liquid 4 He at zero temperature are presented. The sign problem associated to the excited wave function has been dealt both with the fixed-node approximation and the released-node technique. The upper bounds provided by the fixed-node approximation are shown to become exact when using the released-node method. An excellent agreement with experimental data is achieved both at the equilibrium and near the freezing densities.
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تاریخ انتشار 1996