用神经微分方程建模磁化动态,不依赖物理标签也能高效预测。
An Energy-Based Conservative-Dissipative Latent Neural Evolution Operator for Magnetization Dynamics

- 用卷积自编码器结合结构化隐空间微分方程,学习能量势能与耗散机制。
- 在未训练过的长轨迹上,混合对称-反对称模型误差增长更慢,精度显著提升。
- 无需梯度监督或能量标签,仅靠隐空间和解码损失即可训练,推理成本极低。
我们构建了一个基于能量的降维模型,用于微观磁学中的磁化动力学,将卷积自编码器与结构化隐空间神经常微分方程结合。受朗道-利夫希茨-吉尔伯特方程的旋进-耗散结构启发,隐向量场由学习到的标量势能梯度通过反对称算子和对称半正定耗散算子生成。该势能是在非唯一隐坐标下学习的,不等价于吉布斯自由能,但在自治连续时间解中单调递减,而反对称分量允许沿势能等值面运动。编码器、解码器、隐能量及算子通过短轨迹窗口联合训练,仅使用隐空间损失和解码回放损失,无需时间导数监督、物理能量标签或耗散惩罚。推理时,初始状态编码一次,在隐空间演化,仅在请求输出时刻解码,实现比训练数据生成所用微磁求解器更低的轨迹预测开销。我们在两个参数化为场强的测试集上比较了二次型、深度型及加性深度-二次型隐能量,分别对应两种外加场方向(来自NIST μMAG标准问题4)。仅耗散模型与对称-耗散模型在短训练窗口上表现相近,但在无间断回放中差异显著,后者提供更精确的轨迹预测。深度-二次型能量在两种场向下的整体精度最优,且当回放延长至训练范围两倍时,误差增长更缓慢。
原文摘要 · Abstract (English)
We develop an energy-based reduced-order model for micromagnetic magnetization dynamics that couples a convolutional autoencoder to a structured latent neural ordinary differential equation. Motivated by the precessional-dissipative structure of the Landau-Lifshitz-Gilbert equation, the latent vector field is generated from the gradient of a learned scalar potential through an antisymmetric operator and a symmetric positive-semidefinite dissipative operator. This potential is learned in nonunique latent coordinates and is not identified with the Gibbs free energy, but decreases monotonically along autonomous continuous-time solutions, while the antisymmetric component permits motion along its level sets. The encoder, decoder, latent energy, and operators are trained jointly on short trajectory windows using latent and decoded-rollout losses alone, without time-derivative supervision, physical-energy labels, or dissipation penalties. At inference, an initial state is encoded once, evolved in latent space, and decoded only at the requested output times, enabling substantially cheaper trajectory prediction than the micromagnetic solver used to generate the training data. We compare quadratic, deep, and additive deep-quadratic latent energies on two datasets parameterized by field amplitude and generated for the two applied-field directions of the NIST $\mu$MAG Standard Problem 4. Dissipative-only and antisymmetric-dissipative models achieve comparable accuracy on short training-style windows but differ substantially on uninterrupted rollouts, for which the antisymmetric-dissipative models provide markedly more accurate trajectory predictions. The deep-quadratic energy gives the best overall accuracy for both field directions and exhibits slower error growth when rollouts are extended to twice the training horizon.
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