Diagnosing Spectral Ceilings in Equivariant Neural Force Fields
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Abstract (arXiv)
We introduce a spectral-injection diagnostic for measuring which angular frequencies a trained equivariant force-field backbone preserves: inject a controlled angular-frequency perturbation into a molecular force field, attach a lightweight Spectral Prediction Network (SPN) to the frozen backbone, and read off which frequencies are recoverable. On aspirin, a quadratic SPN attached to an L = 2 NequIP backbone recovers the boundary signal at l = 4 but collapses at l = 5: a 11.7x cliff at the predicted drL boundary, with p dropping from 0.913 to 0.078. The same boundary-vs-above contrast persists across n = 4 independently trained backbones (raw-gain delta contrast, hierarchical cluster bootstrap) and is corroborated by a denominator-free injected-residual metric (R2_inj(4) = 0.374 versus R2_inj(5) = 0.006). A finite-degree span theorem calibrates the diagnostic: for a single marked direction, degree-d polynomials of degree-L spherical-harmonic features span exactly H less than or equal to dL with multiplicity-one saturation at the boundary (scoped to single-direction degree-bounded probes, not a function-class upper bound on multi-atom MPNNs). A synthetic C5 calibration plus capacity, activation, and cross-architecture controls rule out parameter count alone as the explanation.
Key facts. No citing papers in the map yet (data through 7 Oct 2026). Builds on 23 of its 40 references that are in the map. First posted on arXiv 8 May 2026.
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References · 23
- 2018On the Spectral Bias of Neural Networkscited by 1,321
- 2018Tensor field networks: Rotation- and translation-equivariant neural networks for 3D point cloudscited by 735
- 2021E(3)-Equivariant Graph Neural Networks for Data-Efficient and Accurate Interatomic Potentialscited by 701
- 2017SchNet: A continuous-filter convolutional neural network for modeling quantum interactionscited by 569
- 2022MACE: Higher Order Equivariant Message Passing Neural Networks for Fast and Accurate Force Fieldscited by 467
- 2018Spherical CNNscited by 452
- 2021Equivariant message passing for the prediction of tensorial properties and molecular spectracited by 438
- 2019Cormorant: Covariant Molecular Neural Networkscited by 262
- 2022Equiformer: Equivariant Graph Attention Transformer for 3D Atomistic Graphscited by 258
- 2022Learning Local Equivariant Representations for Large-Scale Atomistic Dynamicscited by 254
- 2023EquiformerV2: Improved Equivariant Transformer for Scaling to Higher-Degree Representationscited by 201
- 2022e3nn: Euclidean Neural Networkscited by 171
11 more
- 2018Clebsch-Gordan Nets: a Fully Fourier Space Spherical Convolutional Neural Networkcited by 168
- 2021Frame Averaging for Invariant and Equivariant Network Designcited by 166
- 2023Reducing SO(3) Convolutions to SO(2) for Efficient Equivariant GNNscited by 113
- 2022The Design Space of E(3)-Equivariant Atom-Centered Interatomic Potentialscited by 100
- 2023On the Expressive Power of Geometric Graph Neural Networkscited by 89
- 2020On the Universality of Rotation Equivariant Point Cloud Networkscited by 80
- 2023FAENet: Frame Averaging Equivariant GNN for Materials Modelingcited by 72
- 2023TensorNet: Cartesian Tensor Representations for Efficient Learning of Molecular Potentialscited by 53
- 2025The Price of Freedom: Exploring Expressivity and Runtime Tradeoffs in Equivariant Tensor Productscited by 14
- 2023Completeness of Atomic Structure Representationscited by 7
- 2023Wigner kernels: body-ordered equivariant machine learning without a basiscited by 7
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