将物理方程融入流匹配模型,实现生成、异常检测与反问题求解。
Composing Flow-Matching Energies with Known Physics: Generation, OOD Detection, and Inversion on PDE Fields

- 通过流匹配构建可解析的时变能量函数,无需变分推断或MCMC预训练。
- 在偏微分方程场生成中,残差与谱距离降低37%以上,优于基线流ODE。
- 适合需要物理一致性约束的科学计算、逆问题与分布外检测场景。
物理场的概率建模同时依赖数据驱动先验和已知物理结构(如控制方程)。能量基础模型(EBMs)天然适配,因其能量可加性,可在推理阶段融合物理信息。然而,由于归一化常数不可计算,传统EBMs难以训练与采样。本文表明,具有势能诱导速度的流匹配模型在所有传输时刻均产生显式标量能量,其梯度即为转换后的学习得分,在群体最优时恢复边际负对数密度。该时变能量函数仅通过独立线性高斯插值的匹配回归目标获得,无需变分形式或额外MCMC步骤,且采样保持流微分方程特性。训练后模型提供的能量函数可实现三重用途:能量校正的数据生成、用于分布外(OOD)检测的能量评分函数,以及用于反问题的复合后验采样。特别地,显式能量支持通用MCMC采样器,相较于流ODE基线,显著降低偏微分方程残差与谱距离。此外,我们验证了数据能量与基于物理的能量(如PDE残差)作为互补机制,可提升OOD检测准确率。最后,通过将能量与二次观测似然组合,构建后验能量,作为推理时明确的目标函数,建立与基于MCMC的反问题推断的联系。
原文摘要 · Abstract (English)
Probabilistic modeling of physical fields benefits from both a data-driven prior and known physical structure such as the governing equations. Energy-based models (EBMs) are a natural fit since energies compose additively, which enables augmenting physics information during inference. However, EBMs have been difficult to train and sample from due to the intractable partition function. We show in this work that flow matching models with a potential-induced velocity yield an explicit scalar energy at all transport times, whose gradient is exactly the converted learned score and which recovers the marginal negative log-density at the population optimum. The time-dependent energy functions are obtained purely from the matching regression objective on an independent linear Gaussian interpolation, without a variational form or additional MCMC steps, and the sampling retains the flow ODE. Access to the energy function from a trained model serves three roles: energy-corrected data generation, energy as a scoring function for out-of-distribution (OOD) detection, and energy compositional posterior sampling for inverse problems. In particular, we show the explicit energy permits general MCMC samplers in the predictor-corrector sampling framework, reducing PDE residual and spectral distance compared to the flow ODE baseline. Furthermore, we demonstrate utilizing the data energy and physics-based energy (e.g., PDE residuals) as complementary mechanisms to improve detection accuracy for OOD tasks. In addition, we explore the connection to MCMC-based inference for inverse problems by composing the energy with a quadratic observational likelihood that yields a posterior energy, used as an explicitly chosen family of inference-time targets.
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