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Improved diffusion Monte Carlo propagators for bosonic systems using Ito calculus

机译:使用伊藤演算的改进的用于玻色系统的扩散蒙特卡洛传播器

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摘要

The construction of importance sampled diffusion Monte Carlo (DMC) schemes accurate to second order in the time step is discussed. A central aspect in obtaining efficient second order schemes is the numerical solution of the stochastic differential equation (SDE) associated with the Fokker-Plank equation responsible for the importance sampling procedure. In this work, stochastic predictor-corrector schemes solving the SDE and consistent with Ito calculus are used in DMC simulations of helium clusters. These schemes are numerically compared with alternative algorithms obtained by splitting the Fokker-Plank operator, an approach that we analyze using the analytical tools provided by Ito calculus. The numerical results show that predictor-corrector methods are indeed accurate to second order in the time step and that they present a smaller time step bias and a better efficiency than second order split-operator derived schemes when computing ensemble averages for bosonic systems. The possible extension of the predictor-corrector methods to higher orders is also discussed.
机译:讨论了在时间步中精确到二阶的重要采样扩散蒙特卡罗(DMC)方案的构造。获得有效的二阶方案的一个主要方面是与负责重要性抽样程序的福克-普朗克方程相关的随机微分方程(SDE)的数值解。在这项工作中,在氦团簇的DMC模拟中使用了求解SDE并与Ito微积分一致的随机预测器-校正器方案。将这些方案与通过拆分Fokker-Plank运算符获得的替代算法进行了数值比较,该方法是我们使用Ito微积分提供的分析工具进行分析的方法。数值结果表明,预测器-校正器方法的确在时间步长上精确到二阶,并且在计算Bosonic系统的集合平均值时,与二阶分裂算子派生的方案相比,它们呈现出更小的时步偏差和更高的效率。还讨论了将预测器-校正器方法扩展到更高阶的可能性。

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