Neural Operators with Localized Integral and Differential Kernels
Miguel Liu-SchiaffiniJulius BernerBoris BonevThorsten KurthKamyar AzizzadenesheliAnima Anandkumar
Develops discretization-independent localized differential and integral kernel layers for Fourier neural operators, enabling high-resolution local feature capture in PDE modeling and cutting relative prediction error by up to 72% across fluid dynamics benchmarks.
Simulating complex physical systems such as fluid turbulence, weather patterns, and biological processes often demands solving partial differential equations. While traditional numerical simulations require significant computing power, modern deep learning methods known as neural operators offer orders of magnitude speedups. However, existing neural operator models like Fourier neural operators tend to over-smooth solutions and miss fine-scale, local details because they rely primarily on global operations. Conversely, standard convolutional neural networks capture local details well but are constrained to a fixed grid resolution and cannot easily scale to higher-resolution or irregular meshes without losing critical high-frequency information.
The objective of the article is to formulate, prove, and demonstrate a principled neural operator framework that incorporates localized operations—specifically differential and local integral operators—while remaining independent of data grid resolution.
To achieve this, the authors develop two complementary local layers that integrate into existing neural operator frameworks: a differential layer derived from finite-difference stencils that rescales and centers convolutional kernels to converge to exact derivatives as grid spacing shrinks, and a local integral layer based on discrete-continuous convolutions parameterized by basis functions that function across planar, spherical, and unstructured geometries. The researchers evaluate these augmented architectures across five benchmark partial differential equation problems, including 2D Darcy flow, turbulent 2D Navier-Stokes flow, 2D diffusion-reaction systems, spherical shallow water equations, and fluid flow past an irregular cylindrical geometry, maintaining comparable parameter budgets across models to ensure fair comparisons.
The key findings show substantial performance gains across all benchmarks when incorporating local operations. Augmenting Fourier neural operators with both differential and local integral layers reduces relative prediction error by 34% in 2D turbulent Navier-Stokes flow and by 72% in spherical shallow water equations. For the 2D diffusion-reaction equation, the hybrid model cuts relative error by 63% and achieves markedly lower high-frequency errors. In the Darcy flow benchmark, which explicitly mimics a differential operator, the proposed differential kernels improve accuracy over standard Fourier neural operators by 87%. Furthermore, on unstructured meshes modeling flow past a cylinder, the local integral approach outperforms the strongest baseline by 42% while retaining zero-shot super-resolution capabilities across different grid scales.
These findings demonstrate that combining global Fourier convolutions with localized differential and integral kernels overcomes the trade-off between capturing fine-grained physical features and maintaining resolution independence. For engineering and scientific modeling teams, this enables faster, higher-fidelity simulations across varying resolutions without retraining, reducing the computational expense and latency associated with high-resolution forecasting and simulation workflows.
Organizations developing machine learning models for physics simulations should adopt hybrid neural operator architectures that merge global spectral layers with local differential and integral kernels. When configuring models, teams can allocate higher embedding capacity to local branches and use fewer global Fourier modes to improve accuracy without increasing overall parameter counts. Practitioners should also implement discrete-continuous convolutions as encoders and decoders when working with non-uniform or unstructured meshes.
Users should note that differential layers require sufficiently resolved training data; training on under-resolved data can induce discretization errors that compound across deep architectures. Furthermore, Fourier-based components still inherit minor boundary errors in non-periodic domains. Despite these constraints, the high level of experimental consistency across diverse physical domains provides strong confidence in the stability, scalability, and general applicability of the framework.
- Paper: Fourier Neural Operator for Parametric Partial Differential Equations, Zongyi Li et al. (2020). This paper establishes the Fourier neural operator architecture that the source directly augments to address global over-smoothing and capture localized features.
- Paper: Neural Operator: Learning Maps Between Function Spaces With Applications to PDEs, Nikola Kovachki et al. (2023). This work introduces the foundational framework and discretization-invariant properties of neural operators learning mappings between infinite-dimensional function spaces.
- Paper: Convolutional Neural Operators for robust and accurate learning of PDEs, Bogdan Raonic et al. (2023). This paper introduces continuous-discrete equivalent convolutional operators for PDEs, providing essential context for designing resolution-invariant local convolutional layers.
- Paper: Learning nonlinear operators via DeepONet based on the universal approximation theorem of operators, Lu Lu et al. (2021). This seminal paper formulates operator learning via neural networks based on universal approximation theorems between infinite-dimensional function spaces.
- Paper: Beyond Correlation Filters: Learning Continuous Convolution Operators for Visual Tracking, Martin Danelljan et al. (2016). This work formulates continuous convolution operators directly in the continuous domain, offering relevant background for constructing resolution-independent integral kernels.
- Paper: Neural means and kernel corrections for operator learning, Yitzchak Shmalo (2026). This work builds on neural operator formulations, including FNOs, by constructing hybrid architectures that pair neural means with exact kernel ridge regression corrections.
- Paper: Score-Based Diffusion Models in Function Space, Jae Hyun Lim 0001 et al. (2025). This paper extends neural operators in infinite-dimensional function spaces to formulate score-based generative diffusion models for functional PDE data.
