论文标题

粗糙微分方程的单轨迹的逆问题

The Inverse Problem for Single Trajectories of Rough Differential Equations

论文作者

Morrish, Thomas, Papavasiliou, Anastasia, Papamarkou, Theodore, Zhao, Yang

论文摘要

由于需要开发一个通用框架以对离散观察到的随机粗糙微分方程执行统计推断的一般框架,我们的目的是构建一个几何$ p $ -P $ -Rough Path $ {\ bf x} $,其响应$ y $在驱动粗糙的微分方程时,与观察到的轨迹$ y $相匹配。我们将其称为\ textIt {连续的反问题},然后从严格定义其解决方案开始。然后,我们开发一个框架,可以将解决方案作为解决方案的限制,以适当设计\ textIt {离散逆问题},以便融合在$ p $变量中保持。我们的方法基于校准有限变化路径的极限将路径$ x $的粗糙路径“升力”定义为rough路径$ {\ bf x} $的粗糙路径。此外,我们开发了一种通用的数值算法,用于构建离散问题的解决方案。算法的核心思想是使用路径的签名表示,每次根据所需属性进行校正,在响应和控制之间迭代。 我们将我们的框架应用于几何$ p $ -rough路径$ {\ bf x} $的情况下,定义为$ p $ - 变量拓扑中的分段线性路径的限制。我们表达了固定观察率的离散逆问题,作为对分段线性路径驱动的方程系统的解决方案,并证明了与连续反问题的解决方案在观察时间$δ\至0 $的解决方案。最后,我们表明,在这种情况下,用于解决离散反问题的数值算法简化了局部梯度的迭代同时更新,我们证明它相对于$δ$,它在$ p $ variation中均匀地差异。

Motivated by the need to develop a general framework for performing statistical inference for discretely observed random rough differential equations, our aim is to construct a geometric $p$-rough path ${\bf X}$ whose response $Y$, when driving a rough differential equation, matches the observed trajectory $y$. We call this the \textit{continuous inverse problem} and start by rigorously defining its solution. We then develop a framework where the solution can be constructed as a limit of solutions to appropriately designed \textit{discrete inverse problems}, so that convergence holds in $p$-variation. Our approach is based on calibrating the bounded variation paths whose limit defines the rough path `lift' of path $X$ to rough path ${\bf X}$ to the observed trajectory $y$. Moreover, we develop a general numerical algorithm for constructing the solution to the discrete inverse problem. The core idea of the algorithm is to use the signature representation of the path, iterating between the response and the control, each time correcting according to the required properties. We apply our framework to the case where the geometric $p$-rough path ${\bf X}$ is defined as the limit of piecewise linear paths in the $p$-variation topology. We express the discrete inverse problem for a fixed observation rate as a solution to a system of equations driven by piecewise linear paths and prove convergence to the solution of the continuous inverse problem for observation time $δ\to 0$. Finally, we show that, in this context, the numerical algorithm for solving the discrete inverse problem simplifies to an iterative simultaneous update of the local gradients and we prove that it converges in $p$-variation uniformly with respect to $δ$.

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