Uncovering the Laws of Motion: From Chaos to Climate

Author: Denis Avetisyan


A new framework efficiently extracts governing equations from complex data, bridging the gap between observation and fundamental understanding of dynamic systems.

Governing equation identification across chaotic systems-specifically the Sprott and Halvorsen systems-demonstrates that performance, measured as the fraction of successful term recoveries from 100 trials, improves with increasing observational data <span class="katex-eq" data-katex-display="false">n</span> at a signal-to-noise ratio of 49 dB, and surpasses an 80% success rate threshold for Bayesian-ARGOS, ARGOS, and SINDy methods as the signal-to-noise ratio increases at <span class="katex-eq" data-katex-display="false">n=5000</span>.
Governing equation identification across chaotic systems-specifically the Sprott and Halvorsen systems-demonstrates that performance, measured as the fraction of successful term recoveries from 100 trials, improves with increasing observational data n at a signal-to-noise ratio of 49 dB, and surpasses an 80% success rate threshold for Bayesian-ARGOS, ARGOS, and SINDy methods as the signal-to-noise ratio increases at n=5000.

Bayesian-ARGOS combines frequentist screening with Bayesian inference for fast and principled system identification.

Identifying the governing equations of complex systems remains a central challenge in data-driven science, often forcing compromises between automation, statistical rigor, and computational cost. The work ‘Fast and principled equation discovery from chaos to climate’ introduces Bayesian-ARGOS, a hybrid framework that efficiently reconciles these demands by combining frequentist screening with Bayesian inference. This approach enables automated equation discovery with principled uncertainty quantification and demonstrates improved performance-including a two-order-of-magnitude reduction in computational cost-across seven chaotic systems and in high-dimensional climate reconstruction. Can this framework unlock a deeper understanding of latent dynamics across diverse scales, from fundamental physics to global climate patterns?


The Two Paths: First Principles and the Echo of Data

For centuries, scientific advancement has been deeply rooted in the Newtonian approach, a methodology characterized by the derivation of fundamental laws from established theoretical principles. This process often begins with identifying core axioms and then, through mathematical reasoning – frequently utilizing \frac{dy}{dt} = f(y) Ordinary Differential Equations – building predictive models of physical phenomena. Researchers employing this strategy seek to understand why things happen, constructing explanations based on universal truths rather than simply observing what happens. This ‘first principles’ thinking, exemplified by classical mechanics and much of early physics, prioritizes a logically consistent framework, allowing for generalization and prediction even in scenarios not directly studied – a hallmark of successful scientific theory.

Many intricate systems, from weather patterns to financial markets, defy explanation through purely theoretical ‘first principles’ approaches. Instead, a Keplerian approach-named for Johannes Kepler’s discovery of planetary motion-proves invaluable. This method prioritizes the meticulous observation of empirical data, seeking patterns and relationships before attempting to formulate overarching laws. Rather than deducing behavior from established equations, researchers employing this strategy allow the data itself to reveal the underlying structure, often uncovering unexpected correlations and phenomena. This inductive reasoning is particularly crucial when dealing with systems exhibiting emergent behavior, where the whole is demonstrably more than the sum of its parts, and traditional modeling falls short of capturing the full complexity. The Keplerian approach, therefore, isn’t a rejection of theory, but a pragmatic acknowledgement that, in certain cases, observation must precede, and ultimately inform, the development of robust and accurate models.

The pursuit of robust models in science increasingly demands reconciliation between first-principles reasoning and data-driven analysis. Historically, a Newtonian approach-building from established physical laws and \text{OrdinaryDifferentialEquations}-provided a solid foundation, yet struggles with the inherent complexity of many real-world systems. Conversely, the Keplerian approach excels at uncovering patterns within empirical data, but often lacks predictive power beyond the observed conditions. The central challenge, therefore, lies not simply in applying both methodologies, but in developing frameworks that allow them to inform and constrain one another. Successful integration requires techniques capable of translating theoretical predictions into testable hypotheses against observational data, and conversely, extracting underlying principles from complex datasets – a synergistic process vital for advancing understanding and forecasting in fields ranging from climate science to epidemiology.

Bayesian-ARGOS identifies parsimonious ordinary differential equations from noisy state trajectories by adaptively smoothing data, performing frequentist screening with automated parameter selection and pruning, applying Hamiltonian Monte Carlo sampling to a refined design matrix, and supplementing the results with statistical diagnostics to detect model misspecification.
Bayesian-ARGOS identifies parsimonious ordinary differential equations from noisy state trajectories by adaptively smoothing data, performing frequentist screening with automated parameter selection and pruning, applying Hamiltonian Monte Carlo sampling to a refined design matrix, and supplementing the results with statistical diagnostics to detect model misspecification.

The Illusion of Simplicity: Sparse Regression as a Tool for Revelation

Sparse Regression provides a method for creating simplified models of complex systems by representing them as a linear combination of predefined basis functions. This approach assumes that only a small subset of these functions are actually needed to accurately describe the system’s behavior; the remaining terms are considered negligible. The technique aims to identify this crucial subset by minimizing a cost function that balances model fit with the desire for sparsity – that is, a small number of non-zero coefficients. Mathematically, this is often achieved through L1 regularization – also known as the Lasso penalty – which encourages coefficients to be driven towards zero. The basis functions themselves can represent various physical laws, polynomial terms, or other relevant components, and their selection is crucial for the effectiveness of the regression. The resulting model, composed of only the significant terms, offers both computational efficiency and improved interpretability compared to models that include all possible terms.

Library-based sparse regression improves upon standard sparse regression techniques by explicitly defining a library of candidate functions representing potential terms in the governing equations. This approach shifts the focus from searching across an unbounded space of possible functions to selecting the most relevant combinations from a pre-defined, physically informed set. The library is constructed based on domain knowledge and can include nonlinear terms, interactions between variables, and temporal or spatial derivatives. By constraining the search to this library, the method reduces computational cost, improves model interpretability, and enhances the likelihood of identifying the true underlying dynamics of the system, even with limited data.

Adaptive Lasso techniques enhance variable selection in sparse regression by weighting the penalty applied to each coefficient during model fitting. Unlike standard Lasso, which uses a uniform penalty, Adaptive Lasso assigns penalties inversely proportional to coefficient estimates, effectively shrinking less important variables more aggressively. This weighting scheme allows for consistent selection of the true model under certain conditions, improving the accuracy of identified governing equations and resulting in more parsimonious models – those with fewer, but more relevant, terms. Consequently, Adaptive Lasso facilitates increased interpretability by focusing on the dominant dynamics within the system being modeled, reducing the impact of noise and irrelevant features.

Bayesian-ARGOS enhances SINDy-SHRED by functioning as a latent forecaster, providing probabilistic dynamics coefficients and uncertainty-aware predictions decoded from low-dimensional latent states derived from sparse sensor data.
Bayesian-ARGOS enhances SINDy-SHRED by functioning as a latent forecaster, providing probabilistic dynamics coefficients and uncertainty-aware predictions decoded from low-dimensional latent states derived from sparse sensor data.

The Rigor of Validation: Testing Our Reflections

Frequentist inference, a core component of statistical modeling, establishes a framework for assessing model performance through the repeated sampling distribution. This approach defines probability as the long-run frequency of an event and utilizes p-values – the probability of observing results as extreme as, or more extreme than, those actually observed, assuming the null hypothesis is true – to evaluate the statistical significance of model parameters and predictions. Confidence intervals, derived from the sampling distribution, quantify the uncertainty associated with parameter estimates, providing a range within which the true population parameter is likely to lie with a specified level of confidence (e.g., 95%). Hypothesis testing, a key application of frequentist inference, allows for objective decision-making regarding model validity and the acceptance or rejection of specific hypotheses about the underlying data-generating process. The reliability of frequentist inference is predicated on the assumption of independent and identically distributed (i.i.d.) data and a sufficiently large sample size to ensure the validity of asymptotic approximations.

Information criteria, including the Bayesian Information Criterion (BIC), provide a means of model selection by evaluating the trade-off between a model’s goodness of fit and its complexity. BIC, calculated as -2\log(\hat{L}) + k\log(n) , where \hat{L} is the maximized value of the likelihood function, k is the number of parameters estimated in the model, and n is the number of data points, penalizes models with more parameters. Lower BIC values indicate a better model, favoring simpler models unless the increase in complexity is sufficiently justified by a substantial improvement in fit to the data. This approach helps to prevent overfitting and promotes generalization to unseen data by selecting models that achieve an optimal balance between accuracy and parsimony.

Ensemble methods improve predictive performance and robustness by strategically combining multiple individual models. This is achieved through techniques such as averaging predictions – where the outputs of each model are averaged to produce a final prediction – or through more complex weighting schemes that prioritize models with higher historical accuracy. The underlying principle is that the errors of individual models are not necessarily correlated; therefore, combining them reduces overall variance and improves generalization to unseen data. Common ensemble techniques include bagging, boosting, and stacking, each employing a different strategy for model combination and weighting to optimize predictive stability and accuracy.

Benchmarking on the Aizawa system reveals that Bayesian-ARGOS outperforms ARGOS and SINDy in identifying system dynamics, achieving higher success rates with fewer observations and demonstrating reduced collinearity and spurious term inclusion, though residual analysis indicates emerging heteroscedasticity at higher signal-to-noise ratios <span class="katex-eq" data-katex-display="false">SNR</span>.
Benchmarking on the Aizawa system reveals that Bayesian-ARGOS outperforms ARGOS and SINDy in identifying system dynamics, achieving higher success rates with fewer observations and demonstrating reduced collinearity and spurious term inclusion, though residual analysis indicates emerging heteroscedasticity at higher signal-to-noise ratios SNR.

BayesianARGOS: A Synthesis of Approaches

BayesianARGOS presents a novel strategy for automated model discovery by intelligently integrating the strengths of frequentist and Bayesian statistical approaches. Initially, frequentist screening rapidly narrows the vast search space of potential models, identifying candidates most likely to be relevant. This pre-selection dramatically reduces the computational burden, paving the way for a more detailed Bayesian inference stage. Bayesian inference then rigorously evaluates these shortlisted models, quantifying uncertainty and providing a statistically sound basis for selection. This hybrid methodology not only enhances computational efficiency, enabling the analysis of complex systems with limited data, but also delivers a more robust and reliable model discovery process compared to relying on either approach in isolation. The framework’s design prioritizes both speed and statistical rigor, facilitating insights in scenarios where traditional methods prove computationally intractable.

BayesianARGOS distinguishes itself by strategically integrating frequentist and Bayesian statistical methods, a combination particularly effective when dealing with datasets characterized by limited observations. Frequentist screening rapidly narrows the scope of potential relationships, discarding improbable connections before detailed analysis. This pre-selection process dramatically reduces the computational burden, allowing the subsequent Bayesian inference to focus on a more manageable set of hypotheses. By leveraging the strengths of both paradigms – the speed of frequentist methods and the robustness of Bayesian inference – the framework can uncover complex, non-linear relationships that might be missed by either approach alone, even when faced with sparse or noisy data. The result is a powerful tool for model discovery, capable of extracting meaningful insights from challenging datasets where traditional methods falter.

Analysis of SeaSurfaceTemperature data using BayesianARGOS has successfully uncovered crucial drivers of climate patterns through a novel combination of techniques. The framework constructs compact, informative representations of the data within a LatentSpace, subsequently employing sparse regression to pinpoint the most influential factors. This approach demonstrates an 80% success rate in identifying key relationships within benchmark chaotic systems – a significant improvement over traditional methods. Notably, BayesianARGOS achieves this enhanced performance with a remarkable 100x computational speedup compared to its predecessor, ARGOS, making it a powerful tool for complex climate modeling and prediction.

Combining Bayesian-ARGOS with SINDy-SHRED enhances the identification of underlying dynamics and improves long-horizon forecasts of global sea surface temperature, as demonstrated by reduced reconstruction RMSE in latent spaces, accurate trajectory simulations, and reliable decoded forecasts with minimal error over extended lead times.
Combining Bayesian-ARGOS with SINDy-SHRED enhances the identification of underlying dynamics and improves long-horizon forecasts of global sea surface temperature, as demonstrated by reduced reconstruction RMSE in latent spaces, accurate trajectory simulations, and reliable decoded forecasts with minimal error over extended lead times.

The pursuit of governing equations, as detailed in this work, isn’t about imposing order but revealing the latent structure already present within chaotic systems. It’s a subtle distinction, but crucial. One might recall Marvin Minsky’s observation: “The question isn’t ‘can a machine think?’ but ‘what does it mean to think at all?’” Similarly, this framework doesn’t create models of dynamical systems; it uncovers the relationships already evolving. The Bayesian-ARGOS method, with its emphasis on sparse regression and Bayesian inference, acknowledges that long stability isn’t the goal-it’s a symptom of a system failing to adapt. true understanding comes from mapping the inevitable evolution, not preventing it.

What’s Next?

The pursuit of governing equations from data, as exemplified by Bayesian-ARGOS, is not a quest for truth, but a temporary reprieve from uncertainty. Each discovered equation is, at best, a localized model-a fragile scaffolding built upon the assumption that the present will resemble the past. The framework rightly addresses the computational demands of system identification, but sidesteps the more fundamental issue: all models are wrong, some are useful for a time. The true challenge lies not in improving the algorithms, but in accepting the inevitability of model failure and designing systems resilient to it.

Future work will inevitably focus on extending the applicability of these methods to higher-dimensional, more complex systems. However, the real progress will come from acknowledging that data-driven discovery is not about finding ‘the’ equation, but about building a portfolio of equations-a dynamic library of approximations that can adapt to changing conditions. There are no best practices-only survivors. The focus must shift from precision to robustness, from identifying latent dynamics to anticipating their eventual divergence.

Ultimately, this line of inquiry reveals a profound truth: order is just cache between two outages. The goal is not to eliminate chaos, but to learn to navigate it. The next generation of tools will not be about prediction, but about controlled improvisation-systems that can gracefully degrade in the face of the inevitable, unpredictable shifts in the underlying dynamics.


Original article: https://arxiv.org/pdf/2604.11929.pdf

Contact the author: https://www.linkedin.com/in/avetisyan/

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2026-04-16 02:23