arXiv:2511.22819math.APcs.LG2025-11被引 1

用神经网络解决流体方程中极端梯度难题,实现高精度数值验证。

Resolving Sharp Gradients of Unstable Singularities to Machine Precision via Neural Networks

  • 设计梯度归一化残差重加权策略,缓解尖锐梯度对训练的干扰。
  • 在多阶段神经网络下,残差降至舍入误差水平,精度达双浮点机器精度。
  • 发现新奇不稳定的孤子解,助力非线性偏微分方程的数值与证明衔接。

近期工作结合嵌入式数学结构、先进优化与神经网络架构,发现了不可压缩多孔介质(IPM)和二维布辛涅斯克系统等多个关键流体动力学方程的不稳定自相似解。尽管该框架证实了这些奇点的存在,但仅对1维科尔多巴-科尔多巴-丰特洛斯模型的稳定解及第一类不稳定解实现了接近双浮点机器精度的数值精度。对于具有极端梯度的高不稳定解,精度仍不足以验证。主要障碍在于尖锐解梯度引发大而局部的偏微分方程(PDE)残差,不仅阻碍收敛,还掩盖了原点附近用于识别自相似缩放参数λ的关键信号。本文提出一种梯度归一化的PDE残差重加权方案,在保留关键残差信号的同时解决高梯度挑战。结合多阶段神经网络架构,使此前发现的多种不稳定自相似奇点的残差降低至舍入误差水平。此外,本方法成功揭示了IPM方程的第4类不稳定解以及非线性薛定谔方程的新一类高度不稳定孤子解,实现了高梯度解的高精度求解,为非线性偏微分方程中不稳定现象的数值发现与计算机辅助证明之间的鸿沟提供了关键支撑。

原文摘要 · Abstract (English)

Recent work introduced a robust computational framework combining embedded mathematical structures, advanced optimization, and neural network architecture, leading to the discovery of multiple unstable self-similar solutions for key fluid dynamics equations, including the Incompressible Porous Media (IPM) and 2D Boussinesq systems. While this framework confirmed the existence of these singularities, an accuracy level approaching double-float machine precision was only achieved for stable and 1st unstable solutions of the 1D Córdoba-Córdoba-Fontelos model. For highly unstable solutions characterized by extreme gradients, the accuracy remained insufficient for validation. The primary obstacle is the presence of sharp solution gradients. Those gradients tend to induce large, localized PDE residuals during training, which not only hinder convergence, but also obscure the subtle signals near the origin required to identify the correct self-similar scaling parameter lambda of the solutions. In this work, we introduce a gradient-normalized PDE residual re-weighting scheme to resolve the high-gradient challenge while amplifying the critical residual signals at the origin for lambda identification. Coupled with the multi-stage neural network architecture, the PDE residuals are reduced to the level of round-off error across a wide spectrum of unstable self-similar singularities previously discovered. Furthermore, our method enables the discovery of new highly unstable singularities, i.e. the 4th unstable solution for IPM equations and a novel family of highly unstable solitons for the Nonlinear Schrödinger equations. This results in achieving high-gradient solutions with high precision, providing an important ingredient for bridging the gap between numerical discovery and computer-assisted proofs for unstable phenomena in nonlinear PDEs.

神经网络偏微分方程数值精度奇异解

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