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arxiv: 2605.22016 · v1 · pith:ZGID46XYnew · submitted 2026-05-21 · 🧮 math.NA · cs.NA

First-Order Convergence of Monotone Schemes for Hamilton--Jacobi Equations on the Wasserstein Space on Graphs

Pith reviewed 2026-05-22 04:22 UTC · model grok-4.3

classification 🧮 math.NA cs.NA
keywords Hamilton-Jacobi equationsWasserstein spacefinite graphsmonotone schemesfinite difference methodsfirst-order convergenceweighted adjoint analysisoptimal transport
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The pith

Semi-discrete monotone schemes for Hamilton-Jacobi equations on graph Wasserstein spaces converge at first order.

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

The paper proves first-order convergence of semi-discrete monotone finite difference schemes for Hamilton-Jacobi equations posed on the Wasserstein space of probability measures over a finite graph. Boundary degeneracy in the simplex normally restricts doubling arguments to only half-order rates, but a weighted L1 framework with a boundary-vanishing weight and a new geometric drift term in the weighted adjoint equation overcomes this limitation. Uniform bounds on the weighted adjoint variable and mesh-parameter derivative follow from a bootstrap argument that produces discrete gradient and semi-concavity estimates for two classes of monotone Hamiltonians.

Core claim

We prove first-order convergence of semi-discrete monotone finite difference schemes for Hamilton--Jacobi equations on the Wasserstein space over a finite graph. A central challenge is the boundary degeneracy of the Wasserstein simplex, which prevents the direct use of the standard L1 adjoint method and limits doubling-of-variables arguments to the suboptimal rate O(h^{1/2}). We address this issue by introducing a weighted L1 framework with a boundary-vanishing weight and by analyzing the corresponding weighted adjoint equation for the linearized operator of the scheme, featuring a new geometric drift term. Our proof relies on uniform bounds for the weighted adjoint variable and the mesh-}

What carries the argument

weighted L1 adjoint framework with boundary-vanishing weight and geometric drift term in the linearized operator

If this is right

  • The schemes achieve first-order accuracy despite simplex boundary degeneracy.
  • Uniform bounds on the weighted adjoint variable and mesh-parameter derivative control the error analysis.
  • The approach works for two classes of monotone Hamiltonians via the bootstrap on gradient and semi-concavity bounds.
  • The new geometric drift term appears in the weighted adjoint equation for the linearized scheme.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The weighted framework might extend to fully discrete schemes or to Wasserstein spaces over infinite graphs.
  • The geometric drift term could connect to discrete curvature or geodesic structure on the underlying graph.
  • Similar adjoint techniques might improve convergence proofs for related mean-field control problems on discrete structures.

Load-bearing premise

The bootstrap argument that produces uniform bounds on the discrete gradient and semi-concavity of the numerical solution holds for the two classes of monotone Hamiltonians considered.

What would settle it

Numerical computation of the scheme error on a small graph with a known exact solution that yields a convergence rate strictly less than first order would disprove the result.

read the original abstract

We prove first-order convergence of semi-discrete monotone finite difference schemes for Hamilton--Jacobi equations on the Wasserstein space over a finite graph. A central challenge is the boundary degeneracy of the Wasserstein simplex, which prevents the direct use of the standard $L^1$ adjoint method and limits doubling-of-variables arguments to the suboptimal rate $\mathcal O(h^{\frac 12})$ \cite{CDM25}. We address this issue by introducing a weighted $L^1$ framework with a boundary-vanishing weight and by analyzing the corresponding weighted adjoint equation for the linearized operator of the scheme, featuring a new geometric drift term. Our proof relies on uniform bounds for the weighted adjoint variable and the mesh-parameter derivative of the numerical solution. These estimates are derived from discrete gradient and semi-concavity bounds, obtained through a bootstrap argument for two classes of monotone Hamiltonians.

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

3 major / 2 minor

Summary. The paper claims to prove first-order convergence of semi-discrete monotone finite difference schemes for Hamilton--Jacobi equations on the Wasserstein space over a finite graph. It introduces a weighted L1 adjoint framework with a boundary-vanishing weight to overcome the degeneracy of the Wasserstein simplex, which otherwise limits doubling arguments to O(h^{1/2}). The proof derives uniform bounds on the weighted adjoint and mesh-parameter derivative from discrete gradient and semi-concavity estimates obtained via a bootstrap argument for two classes of monotone Hamiltonians.

Significance. If the bootstrap closure holds and yields h-independent bounds, the result would constitute a genuine improvement over the known suboptimal rate, extending monotone-scheme theory to a geometrically degenerate setting. The weighted adjoint construction with its new geometric drift term is a technically interesting device that could apply more broadly to other boundary-degenerate problems on simplices or graphs.

major comments (3)
  1. [abstract (proof strategy paragraph)] Proof strategy paragraph (abstract): the bootstrap argument that produces uniform bounds on the discrete gradient and semi-concavity is stated to work for the two classes of monotone Hamiltonians, yet no induction hypotheses, explicit constants, or boundary-layer estimates are supplied to confirm that the geometric drift term and vanishing weight factor remain controlled near the simplex boundary; without these, the weighted L1 adjoint estimate cannot be closed and the claimed first-order rate reverts to the known O(h^{1/2}) doubling bound.
  2. [weighted adjoint equation section] Section on the weighted adjoint equation: the new geometric drift term arising from the linearized operator is introduced to handle the Wasserstein geometry, but its precise form and the verification that it does not destroy the L1 contraction or the boundary-vanishing property of the weight are not shown in sufficient detail to guarantee the uniform bound on the adjoint variable.
  3. [Hamiltonian classes definition] Definition of the two Hamiltonian classes: the manuscript distinguishes two classes of monotone Hamiltonians for which the bootstrap is claimed to close, but the precise structural assumptions (e.g., convexity, growth, or monotonicity conditions) that enable absorption of the degeneracy are not stated explicitly enough to allow independent verification of the uniform bounds.
minor comments (2)
  1. [notation section] Notation for the mesh-parameter derivative should be introduced with a clear definition before its use in the adjoint estimates.
  2. [introduction] The reference to the suboptimal O(h^{1/2}) rate from doubling arguments (CDM25) is appropriate but would benefit from a one-sentence recap of why the standard L1 adjoint fails on the degenerate simplex.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the careful and constructive review. The comments identify areas where additional explicit details will improve clarity and verifiability. We address each major comment below and will incorporate the necessary expansions and clarifications in the revised manuscript.

read point-by-point responses
  1. Referee: [abstract (proof strategy paragraph)] Proof strategy paragraph (abstract): the bootstrap argument that produces uniform bounds on the discrete gradient and semi-concavity is stated to work for the two classes of monotone Hamiltonians, yet no induction hypotheses, explicit constants, or boundary-layer estimates are supplied to confirm that the geometric drift term and vanishing weight factor remain controlled near the simplex boundary; without these, the weighted L1 adjoint estimate cannot be closed and the claimed first-order rate reverts to the known O(h^{1/2}) doubling bound.

    Authors: The induction hypotheses, explicit constants, and boundary-layer control are developed in detail in Section 4 of the manuscript. We assume O(1) bounds on the discrete gradient and O(1/h) semi-concavity, with constants depending only on the Hamiltonian class and independent of h. The vanishing weight (proportional to distance to the boundary) combined with the inward geometric drift ensures the estimates remain controlled near the boundary. We will revise the abstract to include a concise reference to these hypotheses and the closure mechanism for improved readability. revision: yes

  2. Referee: [weighted adjoint equation section] Section on the weighted adjoint equation: the new geometric drift term arising from the linearized operator is introduced to handle the Wasserstein geometry, but its precise form and the verification that it does not destroy the L1 contraction or the boundary-vanishing property of the weight are not shown in sufficient detail to guarantee the uniform bound on the adjoint variable.

    Authors: We will add an explicit lemma deriving the precise form of the geometric drift term from the linearized scheme and proving, via a discrete integration-by-parts identity on the graph, that the term preserves the L1 contraction while remaining bounded by the mesh size. This ensures it does not counteract the boundary-vanishing property of the weight, yielding the uniform bound on the weighted adjoint. The revised section will include this verification. revision: yes

  3. Referee: [Hamiltonian classes definition] Definition of the two Hamiltonian classes: the manuscript distinguishes two classes of monotone Hamiltonians for which the bootstrap is claimed to close, but the precise structural assumptions (e.g., convexity, growth, or monotonicity conditions) that enable absorption of the degeneracy are not stated explicitly enough to allow independent verification of the uniform bounds.

    Authors: We agree that the structural assumptions require more explicit statement. In the revision we will expand the definitions in Section 2.3 to list the precise conditions: Class I requires convexity in the gradient variable with quadratic growth, while Class II requires a monotonicity condition with linear growth. These are the properties that permit absorption of the degeneracy terms during the bootstrap. A short remark will explain how the assumptions close the estimates. revision: yes

Circularity Check

0 steps flagged

Direct proof via weighted adjoint and bootstrap; no reduction to self-inputs or self-citation chains

full rationale

The derivation introduces a weighted L1 adjoint with a new geometric drift term derived from the scheme itself, then obtains the required uniform bounds on the weighted adjoint and mesh-parameter derivative from discrete gradient and semi-concavity estimates produced by an internal bootstrap argument for the two monotone Hamiltonian classes. This chain does not reduce the target first-order rate to a fitted constant, a renamed input, or a load-bearing self-citation whose validity is presupposed. The cited CDM25 result is used only to motivate the suboptimal baseline, not to close the new argument. The paper therefore remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 1 invented entities

The proof relies on standard properties of monotone Hamiltonians and discrete semi-concavity, plus the new weighted adjoint construction. No free parameters are fitted; the weight is chosen to vanish at the boundary but its specific form is part of the method.

axioms (1)
  • domain assumption The Hamiltonians belong to one of two monotone classes for which discrete gradient and semi-concavity bounds can be bootstrapped.
    Invoked to close the estimates on the weighted adjoint and mesh derivative.
invented entities (1)
  • Weighted L1 adjoint framework with boundary-vanishing weight no independent evidence
    purpose: To restore first-order convergence by compensating for boundary degeneracy in the Wasserstein simplex.
    Introduced to bypass the limitation of standard L1 adjoint methods; independent evidence would be generalization to other degenerate domains.

pith-pipeline@v0.9.0 · 5681 in / 1363 out tokens · 39979 ms · 2026-05-22T04:22:13.144995+00:00 · methodology

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