FINDE: Neural Differential Equations for Finding and Preserving Invariant Quantities

Takashi Matsubara, Takaharu Yaguchi

Keywords: neural ordinary differential equations, first integral, conservetaion law

TL;DR: Real-world dynamical systems have invariant quantities such as energy, momenta, and mass. Even without prior knowledge, the proposed neural network finds and preserves such quantities from data by leveraging projection and discrete gradient methods.

Abstract: Many real-world dynamical systems are associated with first integrals (a.k.a. invariant quantities), which are quantities that remain unchanged over time. The discovery and understanding of first integrals are fundamental and important topics both in the natural sciences and in industrial applications. First integrals arise from the conservation laws of system energy, momentum, and mass, and from constraints on states; these are typically related to specific geometric structures of the governing equations. Existing neural networks designed to ensure such first integrals have shown excellent accuracy in modeling from data. However, these models incorporate the underlying structures, and in most situations where neural networks learn unknown systems, these structures are also unknown. This limitation needs to be overcome for scientific discovery and modeling of unknown systems. To this end, we propose first integral-preserving neural differential equation (FINDE). By leveraging the projection method and the discrete gradient method, FINDE finds and preserves first integrals from data, even in the absence of prior knowledge about underlying structures. Experimental results demonstrate that FINDE can predict future states of target systems much longer and find various quantities consistent with well-known first integrals in a unified manner.

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