Is Flow Matching Just Trajectory Replay for Sequential Data?

Fuente: arXiv
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Main Authors: Lim, Soon Hoe, Lin, Shizheng, Mahoney, Michael W., Erichson, N. Benjamin
Format: Preprint
Published: 2026
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author Lim, Soon Hoe
Lin, Shizheng
Mahoney, Michael W.
Erichson, N. Benjamin
author_facet Lim, Soon Hoe
Lin, Shizheng
Mahoney, Michael W.
Erichson, N. Benjamin
contents Flow matching (FM) is increasingly used in scientific domains for time series generation and forecasting, where data often arise from underlying dynamical systems. However, it is not well-understood whether it learns transferable dynamical structure or simply performs an effective "trajectory replay". We study this question by deriving the velocity field targeted by the empirical FM objective on sequential data in the limit of perfect function approximation. For the Gaussian conditional paths commonly used in practice, we show that the implied sampler is an ODE whose dynamics constitutes a nonparametric, memory-augmented continuous-time dynamical system. The optimal field admits a closed-form expression as a similarity-weighted mixture of instantaneous velocities induced by observed transitions, making the dataset dependence explicit and interpretable. This characterization positions neural FM models as parametric surrogates of an ideal nonparametric solution and suggests practical approximation schemes for robust ODE-based generation. As a byproduct of our analysis, the resulting closed-form sampler, FreeFM, provides strong probabilistic forecasts on nonlinear dynamical system benchmarks directly from historical transitions, without training.
format Preprint
id arxiv_https___arxiv_org_abs_2602_08318
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Is Flow Matching Just Trajectory Replay for Sequential Data?
Lim, Soon Hoe
Lin, Shizheng
Mahoney, Michael W.
Erichson, N. Benjamin
Machine Learning
Chaotic Dynamics
Flow matching (FM) is increasingly used in scientific domains for time series generation and forecasting, where data often arise from underlying dynamical systems. However, it is not well-understood whether it learns transferable dynamical structure or simply performs an effective "trajectory replay". We study this question by deriving the velocity field targeted by the empirical FM objective on sequential data in the limit of perfect function approximation. For the Gaussian conditional paths commonly used in practice, we show that the implied sampler is an ODE whose dynamics constitutes a nonparametric, memory-augmented continuous-time dynamical system. The optimal field admits a closed-form expression as a similarity-weighted mixture of instantaneous velocities induced by observed transitions, making the dataset dependence explicit and interpretable. This characterization positions neural FM models as parametric surrogates of an ideal nonparametric solution and suggests practical approximation schemes for robust ODE-based generation. As a byproduct of our analysis, the resulting closed-form sampler, FreeFM, provides strong probabilistic forecasts on nonlinear dynamical system benchmarks directly from historical transitions, without training.
title Is Flow Matching Just Trajectory Replay for Sequential Data?
topic Machine Learning
Chaotic Dynamics
url https://arxiv.org/abs/2602.08318