用形变框架学习变域偏微分方程的解映射,支持复杂几何变化。
A deformation-based framework for learning solution mappings of PDEs defined on varying domains
- 基于形变构建度量空间,将解映射视为连续映射,用神经网络学习。
- 无需光滑形变,可处理局部几何变化的大系统,理论保证收敛性。
- 兼容线性保持神经算子,适合混合迭代法,适用于多种非光滑区域。
本文建立了一种基于形变的框架,用于学习定义在变化区域上的偏微分方程(PDE)的解映射。通过形变将不同区域上的函数集视为度量空间,解映射被视作从度量到度量的连续映射,并可通过两种策略(D2D与D2E子框架)表示为从度量到巴拿赫空间的连续映射。该映射可由神经网络学习,从而实现对解映射的逼近。本文建立了针对变域PDE解映射学习问题的严格收敛性分析。理论框架依赖若干关键假设,以星形区域为例进行验证,其他情形亦可类似处理。本框架具有三大特点:(1) 不要求区域间微分同胚,仅需同胚即可覆盖广泛区域;(2) 形变映射无需连续,可通过恒等映射与局部形变组合灵活构造,适用于仅部分几何变化的大系统;(3) 若采用保持线性的神经算子(如MIONet),对线性PDE仍能保持源项的线性性,可用于混合迭代方法。最后通过多个数值实验验证了理论结果。
原文摘要 · Abstract (English)
In this work, we establish a deformation-based framework for learning solution mappings of PDEs defined on varying domains. The union of functions defined on varying domains can be identified as a metric space according to the deformation, then the solution mapping is regarded as a continuous metric-to-metric mapping, and subsequently can be represented by another continuous metric-to-Banach mapping using two different strategies, referred to as the D2D subframework and the D2E subframework, respectively. We point out that such a metric-to-Banach mapping can be learned by neural networks, hence the solution mapping is accordingly learned. With this framework, a rigorous convergence analysis is built for the problem of learning solution mappings of PDEs on varying domains. As the theoretical framework holds based on several pivotal assumptions which need to be verified for a given specific problem, we study the star domains as a typical example, and other situations could be similarly verified. There are three important features of this framework: (1) The domains under consideration are not required to be diffeomorphic, therefore a wide range of regions can be covered by one model provided they are homeomorphic. (2) The deformation mapping is unnecessary to be continuous, thus it can be flexibly established via combining a primary identity mapping and a local deformation mapping. This capability facilitates the resolution of large systems where only local parts of the geometry undergo change. (3) If a linearity-preserving neural operator such as MIONet is adopted, this framework still preserves the linearity of the surrogate solution mapping on its source term for linear PDEs, thus it can be applied to the hybrid iterative method. We finally present several numerical experiments to validate our theoretical results.
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