The Lifecycle of the Spectral Edge: From Gradient Learning to Weight-Decay Compression
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Abstract (arXiv)
We decompose the spectral edge -- the dominant direction of the Gram matrix of parameter updates -- into its gradient and weight-decay components during grokking in two sequence tasks (Dyck-1 and SCAN). We find a sharp two-phase lifecycle: before grokking the edge is gradient-driven and functionally active; at grokking, gradient and weight decay align, and the edge becomes a compression axis that is perturbation-flat yet ablation-critical (>4000x more impactful than random directions). Three universality classes emerge (functional, mixed, compression), predicted by the gap flow equation. Nonlinear probes show information is re-encoded, not lost (MLP R2=0.99 where linear R2=0.86), and removing weight decay post-grok reverses compression while preserving the algorithm.
Key facts. Cited by 1 paper in the map (data through 14 Oct 2026). Builds on 14 of its 24 references that are in the map. First posted on arXiv 8 Apr 2026.
Builds on
14 of 24 references.
References · 14
- 2023Progress measures for grokking via mechanistic interpretabilitycited by 839
- 2022Grokking: Generalization Beyond Overfitting on Small Algorithmic Datasetscited by 629
- 2021Gradient Descent on Neural Networks Typically Occurs at the Edge of Stabilitycited by 427
- 2019Gradient Descent Maximizes the Margin of Homogeneous Neural Networkscited by 320
- 2017Empirical Analysis of the Hessian of Over-Parametrized Neural Networkscited by 290
- 2022Towards Understanding Grokking: An Effective Theory of Representation Learningcited by 230
- 2018Gradient Descent Happens in a Tiny Subspacecited by 217
- 2023Dichotomy of Early and Late Phase Implicit Biases Can Provably Induce Grokkingcited by 80
- 2026Low-Dimensional and Transversely Curved Optimization Dynamics in Grokkingcited by 11
- 2026The Geometry of Multi-Task Grokking: Transverse Instability, Superposition, and Weight Decay Phase Structurecited by 9
- 2026Low-Dimensional Execution Manifolds in Transformer Learning Dynamics: Evidence from Modular Arithmetic Taskscited by 7
- 2026Early-Warning Signals of Grokking via Loss-Landscape Geometrycited by 7
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