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arxiv: 2604.11375 · v2 · submitted 2026-04-13 · 🧮 math.NA · cs.NA

Recognition: unknown

DiLO: Decoupling Generative Priors and Neural Operators via Diffusion Latent Optimization for Inverse Problems

Guang Lin, Haibo Liu

Pith reviewed 2026-05-10 15:54 UTC · model grok-4.3

classification 🧮 math.NA cs.NA
keywords diffusion modelsinverse problemsneural operatorsPDE constraintsgenerative priorslatent optimizationmanifold consistencysurrogate solvers
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The pith

DiLO converts stochastic diffusion sampling into deterministic latent optimization to keep neural operators on physical manifolds for inverse problems.

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

The paper establishes that diffusion models provide flexible generative priors for PDE inverse problems but break when neural operator surrogates are applied to intermediate noisy states. DiLO solves this by turning the sampling process into an optimization trajectory over the initial latent variable, so the surrogate is always evaluated only on fully denoised physical parameters. This satisfies the manifold consistency requirement, permits stable gradient flow from measurements back to the latent start, and yields more accurate reconstructions. Experiments on electrical impedance tomography, inverse scattering, and inverse Navier-Stokes problems show gains in accuracy, speed, and noise robustness, backed by convergence theory.

Core claim

DiLO transforms the stochastic sampling process into a deterministic latent trajectory, enabling stable backpropagation of measurement gradients to the initial latent state. By keeping the trajectory on the physical manifold, it ensures physically valid updates and improves reconstruction accuracy while providing theoretical guarantees for convergence.

What carries the argument

Diffusion Latent Optimization (DiLO), which replaces stochastic diffusion sampling with deterministic optimization over the initial latent variable to enforce evaluation of neural surrogates exclusively on fully denoised physical states.

If this is right

  • Reconstruction accuracy improves because updates remain on the physical manifold at every step.
  • Measurement gradients propagate stably back to the initial latent without out-of-distribution evaluations.
  • The approach applies across Electrical Impedance Tomography, Inverse Scattering, and Inverse Navier-Stokes without retraining paired datasets.
  • Convergence of the latent trajectory is guaranteed under the stated theoretical conditions.

Where Pith is reading between the lines

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

  • The same latent-optimization idea could be tested on other generative priors such as flow-based models for the same inverse problems.
  • Running DiLO on experimental sensor data instead of synthetic measurements would check robustness outside simulated settings.
  • Extending the manifold consistency idea to time-evolving or high-dimensional PDEs not included in the current experiments could reveal further limits.

Load-bearing premise

Neural operator surrogates produce unreliable results when evaluated on partially denoised, non-physical intermediate states during diffusion sampling.

What would settle it

Demonstrating that a standard diffusion sampler with neural operators applied at every step achieves comparable accuracy and convergence on the same inverse problems without latent optimization.

Figures

Figures reproduced from arXiv: 2604.11375 by Guang Lin, Haibo Liu.

Figure 1
Figure 1. Figure 1: The DiLO framework. (A) Offline Training: Pre-training the Latent Diffusion Model (LDM) to serve as a plug-and-play prior, alongside a Differentiable Surrogate (e.g., FNO) acting as a forward physics operator. (B) Online Inference: Solving the inverse problem via deterministic latent optimization, where precise gradients from the measurement loss are backpropagated to the initial noise zT . where zt = √ α¯… view at source ↗
Figure 2
Figure 2. Figure 2: Detailed iterative reconstruction of the conductivity distribution for EIT. [PITH_FULL_IMAGE:figures/full_fig_p013_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Detailed iterative reconstruction of the scattering contrast. [PITH_FULL_IMAGE:figures/full_fig_p014_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Detailed iterative reconstruction of the initial vorticity field for the Inverse N-S problem. [PITH_FULL_IMAGE:figures/full_fig_p014_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Qualitative comparison of reconstruction results. [PITH_FULL_IMAGE:figures/full_fig_p015_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Qualitative comparison of reconstruction robustness under 50% Gaussian noise. [PITH_FULL_IMAGE:figures/full_fig_p016_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Reconstruction analysis for a GT characterized by prominent, large-scale internal struc [PITH_FULL_IMAGE:figures/full_fig_p016_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: Reconstruction analysis for a GT featuring multiple closely spaced, distinct anatomical [PITH_FULL_IMAGE:figures/full_fig_p017_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: Reconstruction analysis for an abdominal GT containing small, localized high-contrast [PITH_FULL_IMAGE:figures/full_fig_p017_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: Reconstruction analysis for a chest GT exhibiting large, low-conductivity lung fields [PITH_FULL_IMAGE:figures/full_fig_p017_10.png] view at source ↗
Figure 11
Figure 11. Figure 11: Reconstruction analysis for sparse cell structures with heterogeneous internal contrasts, [PITH_FULL_IMAGE:figures/full_fig_p018_11.png] view at source ↗
Figure 12
Figure 12. Figure 12: Reconstruction analysis for a tightly packed cluster of biological-like cells, confirming [PITH_FULL_IMAGE:figures/full_fig_p018_12.png] view at source ↗
Figure 13
Figure 13. Figure 13: Reconstruction analysis for an initial vorticity field generated via a Gaussian random [PITH_FULL_IMAGE:figures/full_fig_p019_13.png] view at source ↗
Figure 14
Figure 14. Figure 14: Reconstruction analysis for a GRF-generated vorticity field characterized by a highly [PITH_FULL_IMAGE:figures/full_fig_p019_14.png] view at source ↗
Figure 15
Figure 15. Figure 15: Reconstruction analysis for a chaotic, multi-scale vorticity distribution sampled from [PITH_FULL_IMAGE:figures/full_fig_p019_15.png] view at source ↗
Figure 16
Figure 16. Figure 16: Reconstruction analysis for a large-scale, coherent vortex structure originating from a [PITH_FULL_IMAGE:figures/full_fig_p019_16.png] view at source ↗
Figure 17
Figure 17. Figure 17: Robustness analysis under 50% observation noise. [PITH_FULL_IMAGE:figures/full_fig_p020_17.png] view at source ↗
read the original abstract

Diffusion models have emerged as powerful generative priors for solving PDE-constrained inverse problems. Compared to end-to-end approaches relying on massive paired datasets, explicitly decoupling the prior distribution of physical parameters from the forward physical model, a paradigm often formalized as Plug-and-Play (PnP) priors, offers enhanced flexibility and generalization. To accelerate inference within such decoupled frameworks, fast neural operators are employed as surrogate solvers. However, directly integrating them into standard diffusion sampling introduces a critical bottleneck: evaluating neural surrogates on partially denoised, non-physical intermediate states forces them into out-of-distribution (OOD) regimes. To eliminate this, the physical surrogate must be evaluated exclusively on the fully denoised parameter, a principle we formalize as the Manifold Consistency Requirement. To satisfy this requirement, we present Diffusion Latent Optimization (DiLO), which transforms the stochastic sampling process into a deterministic latent trajectory, enabling stable backpropagation of measurement gradients to the initial latent state. By keeping the trajectory on the physical manifold, it ensures physically valid updates and improves reconstruction accuracy. We provide theoretical guarantees for the convergence of this optimization trajectory. Extensive experiments across Electrical Impedance Tomography, Inverse Scattering, and Inverse Navier-Stokes problems demonstrate DiLO's accuracy, efficiency, and robustness to noise.

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

1 major / 2 minor

Summary. The paper proposes Diffusion Latent Optimization (DiLO) to address a bottleneck when combining diffusion-based generative priors with neural operators for PDE-constrained inverse problems. It formalizes the Manifold Consistency Requirement (neural operators evaluated only on fully denoised physical parameters) and introduces a deterministic latent trajectory that replaces stochastic diffusion sampling. This enables stable backpropagation of measurement gradients to the initial latent state while preserving physical validity, with claimed theoretical convergence guarantees. Experiments on Electrical Impedance Tomography, Inverse Scattering, and Inverse Navier-Stokes demonstrate gains in accuracy, efficiency, and noise robustness compared to standard approaches.

Significance. If the central construction and convergence analysis hold, the work offers a principled decoupling of pre-trained generative priors from fast physical surrogates, avoiding OOD evaluation issues that plague direct integration. This could improve flexibility and generalization over end-to-end learned solvers while retaining the benefits of diffusion priors for ill-posed inverse problems. The explicit manifold constraint and theoretical guarantees distinguish it from heuristic PnP variants; reproducible code or parameter-free derivations would further strengthen its utility.

major comments (1)
  1. [§4] §4 (theoretical analysis): The convergence guarantee for the DiLO trajectory is stated to follow from keeping updates on the physical manifold, but the proof sketch does not explicitly bound the deviation introduced by the neural operator approximation or the discretization of the latent trajectory; a quantitative error term relating the surrogate accuracy to the final reconstruction error would be needed to support the claim that DiLO improves accuracy over standard sampling.
minor comments (2)
  1. [Abstract] Abstract: The phrase 'transforms the stochastic sampling process into a deterministic latent trajectory' is repeated; a single concise definition early in the abstract would improve readability.
  2. [Experiments] Experiments section: The noise-robustness plots would benefit from error bars over multiple random seeds and a direct comparison table against a vanilla PnP baseline using the same neural operator but without the latent optimization step.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their positive summary, recognition of the work's potential significance, and recommendation for minor revision. We address the single major comment point-by-point below.

read point-by-point responses
  1. Referee: [§4] §4 (theoretical analysis): The convergence guarantee for the DiLO trajectory is stated to follow from keeping updates on the physical manifold, but the proof sketch does not explicitly bound the deviation introduced by the neural operator approximation or the discretization of the latent trajectory; a quantitative error term relating the surrogate accuracy to the final reconstruction error would be needed to support the claim that DiLO improves accuracy over standard sampling.

    Authors: We appreciate the referee's careful reading and agree that strengthening the error analysis would improve the presentation. The current proof in §4 establishes convergence of the deterministic latent optimization to a stationary point on the physical manifold under the manifold consistency requirement, treating the forward model as exact. In the revised manuscript we will augment §4 with an explicit quantitative error bound. The total reconstruction error will be decomposed as the sum of (i) the optimization error along the latent trajectory (which vanishes with increasing steps under the stated assumptions) and (ii) the neural-operator approximation error, controlled by the surrogate's Lipschitz constant restricted to the manifold. This bound will be contrasted with the additional out-of-distribution error incurred by standard diffusion sampling, thereby providing theoretical support for the accuracy gains observed in the experiments. The added analysis remains fully consistent with the existing convergence result and does not alter any claims. revision: yes

Circularity Check

0 steps flagged

No significant circularity detected

full rationale

The paper defines the Manifold Consistency Requirement as the principle that neural surrogates must be evaluated only on fully denoised physical parameters, then constructs DiLO as a deterministic latent trajectory optimization to satisfy it while enabling gradient backpropagation. This is a standard design choice for a new method, not a reduction of the claimed result to its own inputs by construction. No equations or steps are shown to equate a 'prediction' with a fitted parameter, no load-bearing self-citations reduce the central claim, and no ansatz or uniqueness theorem is smuggled in. The derivation remains self-contained with separate theoretical convergence guarantees claimed for the trajectory.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 1 invented entities

The approach relies on the newly introduced requirement and method; no free parameters or standard mathematical axioms are specified in the abstract.

axioms (1)
  • ad hoc to paper Manifold Consistency Requirement that neural operators are only evaluated on fully denoised physical parameters
    Introduced to prevent OOD evaluation of surrogates during diffusion sampling.
invented entities (1)
  • Diffusion Latent Optimization (DiLO) no independent evidence
    purpose: Transforms stochastic diffusion sampling into deterministic latent trajectory optimization
    Proposed method to enable gradient backpropagation while maintaining physical validity.

pith-pipeline@v0.9.0 · 5521 in / 1120 out tokens · 32755 ms · 2026-05-10T15:54:59.338005+00:00 · methodology

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Reference graph

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