论文标题
ITô扩散时间的高阶自适应方法
Higher-order adaptive methods for exit times of Itô diffusions
论文作者
论文摘要
我们构建了一种高阶自适应方法,用于强烈的ITô随机微分方程(SDE)的出口时间。该方法采用强大的ITô-taylor方案来模拟SDE路径,并随着解决方案接近域的边界的数值积分而自适应地降低了数值集成中的步骤。这些技术证明可以很好地相互补充:自适应时间稳定,通过减少数值溶液退出域的过冲的大小来提高退出时间的准确性,而高阶方案改善了扩散过程状态的近似值。我们提出了高阶自适应方法的两个版本。第一个将米尔斯坦方案用作数值集成符,并且在远离边界远时,$ h $和两个步骤尺寸用于自适应时间:$ h $,而$ h^2 $在靠近边界时。第二种方法是使用强的ITô-taylor方案1.5作为数值积分器的延伸方法,三个用于自适应时间步长的步骤尺寸。对于任何$ξ> 0 $,我们证明强错误由$ \ Mathcal {o}(h^{1-ξ})$和$ \ nathcal {o}(h^{3/2-ξ})$分别用于第一和第二种方法的预期计算成本,以及这两种方法的预期计算成本,以及$ \ m nate-mathcal calcal}(o}(H) \ log(h^{ - 1}))$。理论结果由数值示例支持,我们讨论了进一步提高强收敛率的扩展潜力。
We construct a higher-order adaptive method for strong approximations of exit times of Itô stochastic differential equations (SDE). The method employs a strong Itô--Taylor scheme for simulating SDE paths, and adaptively decreases the step-size in the numerical integration as the solution approaches the boundary of the domain. These techniques turn out to complement each other nicely: adaptive time-stepping improves the accuracy of the exit time by reducing the magnitude of the overshoot of the numerical solution when it exits the domain, and higher-order schemes improve the approximation of the state of the diffusion process. We present two versions of the higher-order adaptive method. The first one uses the Milstein scheme as numerical integrator and two step-sizes for adaptive time-stepping: $h$ when far away from the boundary and $h^2$ when close to the boundary. The second method is an extension of the first one using the strong Itô--Taylor scheme of order 1.5 as numerical integrator and three step-sizes for adaptive time-stepping. For any $ξ>0$, we prove that the strong error is bounded by $\mathcal{O}(h^{1-ξ})$ and $\mathcal{O}(h^{3/2-ξ})$ for the first and second method, respectively, and the expected computational cost for both methods is $\mathcal{O}(h^{-1} \log(h^{-1}))$. Theoretical results are supported by numerical examples, and we discuss the potential for extensions that improve the strong convergence rate even further.