Optimal scaling laws in learning hierarchical multi-index models
- URL: http://arxiv.org/abs/2602.05846v1
- Date: Thu, 05 Feb 2026 16:33:51 GMT
- Title: Optimal scaling laws in learning hierarchical multi-index models
- Abstract summary: We derive exact information-theoretic scaling laws for subspace recovery and prediction error.<n>We show that these optimal rates are achieved by a simple, target-agnostic spectral estimator.
- Score: 28.495611422425238
- License: http://creativecommons.org/licenses/by/4.0/
- Abstract: In this work, we provide a sharp theory of scaling laws for two-layer neural networks trained on a class of hierarchical multi-index targets, in a genuinely representation-limited regime. We derive exact information-theoretic scaling laws for subspace recovery and prediction error, revealing how the hierarchical features of the target are sequentially learned through a cascade of phase transitions. We further show that these optimal rates are achieved by a simple, target-agnostic spectral estimator, which can be interpreted as the small learning-rate limit of gradient descent on the first-layer weights. Once an adapted representation is identified, the readout can be learned statistically optimally, using an efficient procedure. As a consequence, we provide a unified and rigorous explanation of scaling laws, plateau phenomena, and spectral structure in shallow neural networks trained on such hierarchical targets.
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