Physics – Condensed Matter – Other Condensed Matter
Scientific paper
2005-01-04
J. Phys. A: Math. Gen. 39 (2006) 2723-2755
Physics
Condensed Matter
Other Condensed Matter
39 pages, 11 figures, 2 tables. Major revision, especially Section 6 (convergence issues) which is almost all new, and also in
Scientific paper
10.1088/0305-4470/39/11/011
First principles simulations of the quantum dynamics of interacting Bose gases using the stochastic gauge representation are analyzed. In a companion paper, we showed how the positive P representation can be applied to these problems using stochastic differential equations. That method, however, is limited by increased sampling error as time evolves. Here, we show how the sampling error can be greatly reduced and the simulation time significantly extended using stochastic gauges. In particular, local stochastic gauges (a subset) are investigated. Improvements are confirmed in numerical calculations of single-, double-, and multi-mode systems in the weak mode coupling regime. Convergence issues are investigated, including the recognition of two modes by which stochastic equations produced by phase space methods in general can diverge: movable singularities and a noise-weight relationship. The example calculated here displays wave-like behaviour in spatial correlation functions propagating in a uniform 1D gas after a sudden change in the coupling constant.This could in principle be tested experimentally using Feshbach resonance methods.
Deuar Piotr
Drummond Peter D.
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