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arxiv: 2604.26933 · v1 · submitted 2026-04-29 · 🧮 math.DS

Recognition: unknown

Data-driven discovery of polynomial ODEs with provably bounded solutions

Albert Alcalde, Giovanni Fantuzzi

Pith reviewed 2026-05-07 09:21 UTC · model grok-4.3

classification 🧮 math.DS
keywords data-driven discoverypolynomial ODEsLyapunov functionsbounded trajectoriessystem identificationnonlinear dynamical systemsoptimization methods
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The pith

A data-driven method recovers polynomial ODEs with provably bounded trajectories by jointly finding the vector field and a certifying Lyapunov function.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper aims to show that it is possible to learn polynomial ordinary differential equations from data in such a way that the learned models are guaranteed to have all trajectories bounded. This is achieved by simultaneously determining the polynomial right-hand side and a polynomial function that serves as a Lyapunov function, thereby defining a compact absorbing set. A sympathetic reader would care because data-driven models without such guarantees can lead to simulations that diverge or behave unrealistically, limiting their reliability in scientific and engineering contexts. The approach solves the resulting nonconvex optimization by alternating between convex subproblems for the vector field coefficients and the Lyapunov coefficients, starting from a data-based initialization. This extends earlier techniques limited to quadratic forms and ellipsoidal bounds to general polynomials.

Core claim

The paper establishes that polynomial ODEs with provably bounded trajectories can be discovered from data through a well-posed nonconvex optimization problem that is solved via an alternating block-coordinate scheme with convex subproblems, enabled by a novel initialization that identifies a candidate Lyapunov function directly from the data.

What carries the argument

The alternating block-coordinate optimization scheme that alternately solves for the coefficients of the polynomial vector field and the polynomial Lyapunov function, with feasibility guaranteed by the initialization procedure.

Load-bearing premise

The load-bearing premise is that the data come from a system whose behavior is well approximated by a low-degree polynomial vector field for which a polynomial Lyapunov function of modest degree can be found through the alternating optimization.

What would settle it

Finding a dynamical system where the true trajectories are bounded but the method either fails to recover a model or returns one without a certifying Lyapunov function, or conversely recovers a model that the method certifies as bounded but which actually has unbounded trajectories.

Figures

Figures reproduced from arXiv: 2604.26933 by Albert Alcalde, Giovanni Fantuzzi.

Figure 1
Figure 1. Figure 1: State-space representation of the two-dimensional cubic system from Section 3.1. The figure shows the vector field f ∗ (gray arrows), the limit cycle (solid black line), the equilibria (black triangles), the absorbing set defined by (3.2) with α = 1 and b = 15 (green shaded region), and the noisy state measurements used for model discovery (blue dots). 3.1. A bounded system with no absorbing ellipsoid. As … view at source ↗
Figure 2
Figure 2. Figure 2: Learned vector fields and corresponding absorbing sets (shaded in green) for Lyapunov function degree dv = 2 and model degrees df = 2, 3, 4, 5. Panels in the bottom row show a zoomed-in view of the box [−3, 3]2 . limit cycle and a certified absorbing ellipsoid. Thus, while the true system does not admit a quadratic Lyapunov function, it can be approximated by one that does, which SILAS recovers. Increasing… view at source ↗
Figure 3
Figure 3. Figure 3: Learned vector fields and corresponding absorbing sets (shaded in green) for Lyapunov function degree dv = 4 and model degrees df = 2, . . . , 9. The bottom row shows zoomed-out views of the panels in the middle row. dimension up to n = 6 and no reported unbounded variables. Of these 109 ODEs, 82 have a polynomial vector field. Some of them, such as the Lorenz system, are known to admit absorbing sets. Oth… view at source ↗
Figure 4
Figure 4. Figure 4: Pointwise 2-norm errors between the exact vector field of the cubic system in Section 3.1 and the vector fields learned with Lyapunov function degree dv = 4 and model degree df = 2, . . . , 9. fixing Λ = 0.1Λ0 and µ = 0.1µ0, where Λ0 and µ0 are selected such that the function z 7→ Λ −1 0 (z − µ0) maps the hypercube [−1, 1]n to a box bounding the training data with a 25% buffer. Precisely, if x max and x mi… view at source ↗
Figure 5
Figure 5. Figure 5: Error distributions (curves) and mean errors (vertical bars) for 82 polynomial ODEs in the dysts library. Colors identify models of degree 2 (■), 3 (■), 4 (■), 5 (■), 6 (■), and 7 (■). Green shading indicates errors smaller than 1%. error is smaller than 1% for 71 of the 82 polynomial systems and for 10 of the 27 non￾polynomial ones. Thus, SILAS works robustly for systems governed by polynomial equations, … view at source ↗
Figure 6
Figure 6. Figure 6: Error distributions (curves) and mean errors (vertical bars) for 27 non-polynomial ODEs in the dysts library. Colors identify models of degree 2 (■), 3 (■), 4 (■), 5 (■), 6 (■), and 7 (■). Green shading indicates errors smaller than 1% view at source ↗
Figure 7
Figure 7. Figure 7: Attractors for selected systems from the dysts library. Top row: The true attrac￾tor. Middle row: Discovered attractors. Bottom row: Discovered attractors and absorbing sets certifying the boundedness of the discovered ODEs. the discovered models are also shown. In all cases, the discovered attractors are topo￾logically similar to the exact ones, showing that SILAS can work well even when the true system d… view at source ↗
Figure 8
Figure 8. Figure 8: Attractors for selected systems from the dysts library, discovered with a refined dataset. Top row: True attractors. Middle row: Discovered attractors. Bottom row: Discov￾ered attractors and absorbing sets certifying the boundedness of the discovered ODEs. there are also cases in which our bounded ODE models are unable to accurately re￾produce the true system dynamics, such as the non-polynomial systems Sp… view at source ↗
Figure 9
Figure 9. Figure 9: Modeled vs. true POD-coefficient dynamics for the PDE example in Section 3.3, projected onto the (x1, x2) plane. The reduced-order models are for n = 3 (left), 4 (middle), and 5 (right) POD modes. Panels in each column show the PDE dynamics (top), the reduced￾order ODE dynamics (middle), and the reduced-order ODE dynamics with their absorbing ellipsoid (bottom). with df = 3 for n = 5 view at source ↗
Figure 10
Figure 10. Figure 10: Reconstructed vs. true r-component of the PDE solution in Section 3.3, obtained from reduced-order models with n = 3 (top), 4 (middle), and 5 (bottom) POD modes. In each row, panels show the reference PDE simulation (left), the reconstruction from the learned ODE model (middle), and the absolute error between the two (right). Lyapunov functions characterizing compact absorbing sets. Concretely, SILAS iden… view at source ↗
read the original abstract

We introduce SILAS, a data-driven framework for discovering polynomial ordinary differential equations (ODEs) with provably bounded trajectories. Boundedness is certified by compact absorbing sets defined via polynomial Lyapunov functions. We jointly identify the ODE vector field and the Lyapunov function using a well-posed nonconvex optimization problem built using polynomial optimization tools. We solve this problem using an alternating block-coordinate optimization scheme with convex subproblems, whose feasibility is ensured by a novel model-agnostic initialization that identifies a candidate Lyapunov function from data. Our methods extend prior approaches for quadratic ODEs with absorbing ellipsoids to a significantly broader class of ODEs and absorbing sets. A suite of over 100 examples demonstrates that SILAS can recover accurate and provably bounded ODE models for a broad range of nonlinear dynamical systems.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript introduces SILAS, a data-driven framework that jointly identifies a polynomial vector field and a polynomial Lyapunov function from trajectory data via a nonconvex optimization problem solved by alternating block-coordinate descent on convex subproblems. Boundedness is certified by the existence of a compact absorbing set defined by the Lyapunov function. The method is initialized with a model-agnostic procedure that finds an initial feasible Lyapunov function, and the approach is validated empirically on a suite of over 100 examples spanning nonlinear dynamical systems.

Significance. If the alternating procedure reliably recovers accurate polynomial models together with valid Lyapunov certificates, the work would meaningfully extend data-driven discovery beyond quadratic ODEs with ellipsoidal bounds, providing explicit safety guarantees useful for control and verification. The scale of the numerical demonstration and the convex-subproblem structure are positive features; however, the absence of convergence analysis or failure-mode quantification limits the strength of the central claim that the method works for the broader class invoked in the abstract.

major comments (2)
  1. [optimization procedure (alternating scheme)] The alternating block-coordinate scheme for the joint nonconvex problem (described in the optimization section following the problem formulation) lacks any convergence analysis, basin characterization, or quantification of how often it reaches points where the data-fit residual remains large or the Lyapunov certificate becomes invalid after rounding. This is load-bearing for the claim that SILAS recovers accurate and provably bounded models on the reported suite, because each block subproblem being convex does not guarantee that alternation avoids stationary points that are feasible yet inaccurate.
  2. [numerical results / examples] No error bars, sensitivity analysis with respect to polynomial degree selection, or statistics on how often the post-hoc degree choice affects certificate validity are provided in the numerical results section. This weakens the assertion of success across more than 100 examples, as the central claim relies on the procedure producing both accurate dynamics and valid certificates without quantifying variability or failure rates.
minor comments (2)
  1. [problem formulation] The notation for the polynomial bases and the precise definition of the absorbing-set radius should be stated more explicitly when first introduced, to avoid ambiguity when comparing to prior quadratic-ODE work.
  2. [figures] A few figure captions in the examples section could more clearly indicate which trajectories are training data versus validation trajectories.

Simulated Author's Rebuttal

2 responses · 2 unresolved

We thank the referee for the constructive review and positive remarks on the framework's scope and numerical demonstration. We respond to each major comment below, indicating where revisions are planned.

read point-by-point responses
  1. Referee: The alternating block-coordinate scheme for the joint nonconvex problem (described in the optimization section following the problem formulation) lacks any convergence analysis, basin characterization, or quantification of how often it reaches points where the data-fit residual remains large or the Lyapunov certificate becomes invalid after rounding. This is load-bearing for the claim that SILAS recovers accurate and provably bounded models on the reported suite, because each block subproblem being convex does not guarantee that alternation avoids stationary points that are feasible yet inaccurate.

    Authors: We acknowledge the absence of a theoretical convergence analysis for the alternating scheme. Each block subproblem is convex and solved to global optimality, while the model-agnostic initialization explicitly constructs a feasible starting Lyapunov function from data. The joint problem remains nonconvex, so global convergence or basin characterization is not available. In revision we will expand the optimization section with a dedicated paragraph discussing these limitations, reporting observed iteration counts and residual behavior across the example suite, and clarifying that the method relies on empirical reliability rather than provable convergence to accurate models. revision: partial

  2. Referee: No error bars, sensitivity analysis with respect to polynomial degree selection, or statistics on how often the post-hoc degree choice affects certificate validity are provided in the numerical results section. This weakens the assertion of success across more than 100 examples, as the central claim relies on the procedure producing both accurate dynamics and valid certificates without quantifying variability or failure rates.

    Authors: The numerical results section reports success on more than 100 examples without error bars, degree-sensitivity studies, or aggregate statistics on post-rounding certificate validity. We agree that such quantification would strengthen the presentation. In the revision we will add a short subsection (or appendix) containing sensitivity results for a representative subset of systems, including the effect of degree choice on certificate validity, and report the fraction of examples in which the rounded Lyapunov function remains valid. Full error bars and exhaustive failure-mode statistics for every example would require substantial additional computation beyond the current scope. revision: partial

standing simulated objections not resolved
  • Theoretical convergence analysis or basin characterization for the nonconvex alternating block-coordinate scheme
  • Comprehensive error bars, sensitivity analysis, and failure-rate statistics across the entire suite of more than 100 examples

Circularity Check

0 steps flagged

No significant circularity in the derivation chain

full rationale

The paper presents SILAS as a new algorithmic framework that formulates a joint nonconvex optimization problem over polynomial vector-field coefficients and a polynomial Lyapunov function, then solves it via alternating convex block-coordinate steps initialized by a model-agnostic procedure. No step in the abstract or described method reduces a claimed prediction, uniqueness result, or boundedness certificate to a fitted parameter or self-citation by construction; the extension of prior quadratic-ODE work is stated as a generalization rather than a load-bearing premise that defines the new result. The central contribution is therefore an empirically validated procedure whose validity rests on the optimization formulation and numerical examples, not on any tautological re-expression of its inputs.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The central claim rests on the existence of a polynomial vector field and a polynomial Lyapunov function of modest degree that can be recovered by the proposed nonconvex program; the abstract does not enumerate explicit free parameters or invented entities.

free parameters (1)
  • polynomial degree for vector field and Lyapunov function
    Chosen to balance expressivity and tractability; not specified numerically in abstract.
axioms (1)
  • domain assumption The underlying system admits a polynomial approximation whose trajectories remain inside a compact absorbing set certified by a polynomial Lyapunov function.
    Invoked implicitly when claiming provable boundedness for the discovered models.

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