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Microscopic calculation of the phonon-roton branch in superfluid 4He

J. Boronat, J. Casulleras

cond-matarXiv:cond-mat/9607206

Abstract

Diffusion Monte Carlo results for the phonon-roton excitation branch in bulk liquid 4He 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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