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arXiv · 2605.26324

Semigroup Consistency as a Diagnostic for Learned Physics Simulators

Lennon J. Shikhman
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Abstract

Learned physics simulators are often evaluated by one-step or short-horizon prediction error, but these metrics can miss failures in temporal composition and long-horizon rollout. For autonomous, state-complete systems, exact solution maps satisfy a semigroup law: direct evolution over $s+t$ should agree with evolution over $s$ followed by $t$. We propose normalized semigroup error as a post hoc, model-agnostic diagnostic comparing these direct and composed learned predictions. On one-dimensional heat and Burgers dynamics with time-conditioned ConvNet and FNO baselines, semigroup error is positively associated with rollout degradation, with trajectory-level Spearman correlation $\rho = 0.635$ and $95%$ CI $[0.621, 0.649]$. Semigroup regularization has mixed effects, supporting semigroup consistency primarily as an evaluation diagnostic rather than a universally beneficial training objective.

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BibTeXRIS

Lennon J. Shikhman. 2026-05-25. Semigroup Consistency as a Diagnostic for Learned Physics Simulators. https://arxiv.org/abs/2605.26324

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